bims-mitdis Biomed News
on Mitochondrial disorders
Issue of 2023–12–03
63 papers selected by
Catalina Vasilescu, Helmholz Munich
  1. Mitochondrial DNA editing with mitoARCUS.
  2. MmisAT and MmisP: an efficient and accurate suite of variant analysis toolkit for primary mitochondrial diseases.
  3. Metabolic control of mitophagy.
  4. Loss of mitochondrial Ca2+ uptake protein 3 impairs skeletal muscle calcium handling and exercise capacity.
  5. Efficient elimination of MELAS-associated m.3243G mutant mitochondrial DNA by an engineered mitoARCUS nuclease.
  6. TFAM mislocalization during spermatogenesis.
  7. Multifaceted Roles of AFG3L2, a Mitochondrial ATPase in Relation to Neurological Disorders.
  8. Review title: Mechanisms of mitochondrial reorganization.
  9. Combined RNA interference and gene replacement therapy targeting MFN2 as proof of principle for the treatment of Charcot-Marie-Tooth type 2A.
  10. Protocol for evaluating mitochondrial morphology changes in response to CCCP-induced stress through open-source image processing software.
  11. Mitochondria possess a large, non-selective ionic current that is enhanced during cardiac injury.
  12. Mitochondrial Transformation of Smooth Muscle Phenotype.
  13. Mitochondrial E3 ligase MARCH5 is a safeguard against DNA-PKcs-mediated immune signaling in mitochondria-damaged cells.
  14. Ataxia Syndrome With Hearing Loss and Nephronophthisis Associated With a Novel Homozygous Variant in XPNPEP3.
  15. Biased placement of Mitochondria fission facilitates asymmetric inheritance of protein aggregates during yeast cell division.
  16. Leber's hereditary optic neuropathy: Update on the novel genes and therapeutic options.
  17. Altered anterograde axonal transport of mitochondria in cultured striatal neurons of a knock-in mouse model of Huntington's disease.
  18. The Effect of Photobiomodulation on the Treatment of Hereditary Mitochondrial Diseases.
  19. Mitochondrial transplantation reduces lower limb ischemia-reperfusion injury by increasing skeletal muscle energy and adipocyte browning.
  20. Mitophagy in human health, ageing and disease.
  21. Cardiovascular Aging: Spotlight on Mitochondria.
  22. Substrate Sequestration and Chain Flipping in Human Mitochondrial Acyl Carrier Protein.
  23. Powering prescription: Mitochondria as "Living Drugs" - Definition, clinical applications, and industry advancements.
  24. Targeting mitochondrial Ca2+ uptake for the treatment of amyotrophic lateral sclerosis.
  25. A new family with a case of severe early-onset muscle fatigue and a peculiar maternally inherited painful swelling in chewing muscles associated with homoplasmic m.15992A>T mutation in mitochondrial tRNAPro.
  26. Analyzing Mitochondrial Function in a Drosophila melanogaster PINK1B9-Null Mutant Using High-resolution Respirometry.
  27. Impaired Mitochondrial Respiration in REM-Sleep Behavior Disorder: A Biomarker of Parkinson's Disease?
  28. Skeletal muscle proteome analysis underpins multifaceted mitochondrial dysfunction in Friedreich's ataxia.
  29. Lowered oxidative capacity in spinal muscular atrophy, Jokela type; comparison with mitochondrial muscle disease.
  30. NGLY1 mutations cause protein aggregation in human neurons.
  31. Interactions of amyloidogenic proteins with mitochondrial protein import machinery in aging-related neurodegenerative diseases.
  32. Role of F-actin-mediated endocytosis and exercise in mitochondrial transplantation in an experimental Parkinson's disease mouse model.
  33. Mitochondrial quality control in health and cardiovascular diseases.
  34. The poxvirus F17 protein counteracts mitochondrially orchestrated antiviral responses.
  35. Methylmalonyl Coenzyme A (CoA) Epimerase Deficiency, an Ultra-Rare Cause of Isolated Methylmalonic Aciduria With Predominant Neurological Features.
  36. Long-term prognosis of fatty-acid oxidation disorders in adults: Optimism despite the limited effective therapies available.
  37. Supercomplex formation of mitochondrial respiratory chain complexes in leukocytes from patients with neurodegenerative diseases.
  38. Multi-phase separation in mitochondrial nucleoids and eukaryotic nuclei.
  39. The clinical, myopathological, and genetic analysis of 155 Chinese mitochondrial ophthalmoplegia patients with mitochondrial DNA single large deletions.
  40. ACO2 deficiency increases vulnerability to Parkinson's disease via dysregulating mitochondrial function and histone acetylation-mediated transcription of autophagy genes.
  41. Real-Time Assessment of Mitochondrial Function in Cytotrophoblast and Syncytialized Trophoblast Cells Using the Seahorse XFe24 Extracellular Flux Analyzer.
  42. Anesthetic Management for a Child With a Newly Identified Mitochondrial Disease SLC25A46 Mutation: A Case Report.
  43. O-GlcNAcylation is essential for therapeutic mitochondrial transplantation.
  44. Skeletal Health in Patients With Mitochondrial Diabetes: Case Series and Review of Literature.
  45. Decoding mitochondrial-nuclear (epi)genome interactions: the emerging role of ncRNAs.
  46. [Expert consensus on the diagnosis and treatment of Leigh syndrome (2023)].
  47. Basal activity of PINK1 and PRKN in cell models and rodent brain.
  48. NR-SAFE: a randomized, double-blind safety trial of high dose nicotinamide riboside in Parkinson's disease.
  49. Living donor liver transplantation for myocerebrohepatopathy spectrum due to POLG mutations.
  50. Negative modulation of mitochondrial calcium uniporter complex protects neurons against ferroptosis.
  51. Improved detection of aberrant splicing with FRASER 2.0 and the intron Jaccard index.
  52. Commentary: Can astrocytic mitochondria therapy be used as antioxidant conditioning to protect neurons?
  53. A modified mouse model of Friedreich's ataxia with conditional Fxn allele homozygosity delays onset of cardiomyopathy.
  54. COQ4 is required for the oxidative decarboxylation of the C1 carbon of Coenzyme Q in eukaryotic cells.
  55. PhenoSV: interpretable phenotype-aware model for the prioritization of genes affected by structural variants.
  56. Case report: Two unexpected cases of DGUOK-related mitochondrial DNA depletion syndrome presenting with hyperinsulinemic hypoglycemia.
  57. Biallelic variants in the COQ4 gene caused hereditary spastic paraplegia predominant phenotype.
  58. The implementation and utility of clinical exome sequencing in a South African infant cohort.
  59. IGF2 deficiency promotes liver aging through mitochondrial dysfunction and upregulated CEBPB signaling in D-galactose-induced aging mice.
  60. Mitochondrial nucleic acids in innate immunity and beyond.
  61. Tiny robots made from human cells heal damaged tissue.
  62. Clinical and genetic analysis of infants with Pontocerebellar Hypoplasia Type 6 caused by RARS2 variations.
  63. Adjust the format of papers to improve description by AI.
  1. Nat Metab. 2023 Nov 30.
    Mitochondrial DNA editing with mitoARCUS.
    Denisa Hathazi, Rita Horvath.
      
    DOI:  https://doi.org/10.1038/s42255-023-00933-5
  2. Hum Genomics. 2023 Nov 27. 17(1): 108
    MmisAT and MmisP: an efficient and accurate suite of variant analysis toolkit for primary mitochondrial diseases.
    Shuangshuang Huang, Zhaoyu Wu, Tong Wang, Rui Yu, Zhijian Song, Hao Wang.
      Recent advances in next-generation sequencing (NGS) technology have greatly accelerated the need for efficient annotation to accurately interpret clinically relevant genetic variants in human diseases. Therefore, it is crucial to develop appropriate analytical tools to improve the interpretation of disease variants. Given the unique genetic characteristics of mitochondria, including haplogroup, heteroplasmy, and maternal inheritance, we developed a suite of variant analysis toolkits specifically designed for primary mitochondrial diseases: the Mitochondrial Missense Variant Annotation Tool (MmisAT) and the Mitochondrial Missense Variant Pathogenicity Predictor (MmisP). MmisAT can handle protein-coding variants from both nuclear DNA and mtDNA and generate 349 annotation types across six categories. It processes 4.78 million variant data in 76 min, making it a valuable resource for clinical and research applications. Additionally, MmisP provides pathogenicity scores to predict the pathogenicity of genetic variations in mitochondrial disease. It has been validated using cross-validation and external datasets and demonstrated higher overall discriminant accuracy with a receiver operating characteristic (ROC) curve area under the curve (AUC) of 0.94, outperforming existing pathogenicity predictors. In conclusion, the MmisAT is an efficient tool that greatly facilitates the process of variant annotation, expanding the scope of variant annotation information. Furthermore, the development of MmisP provides valuable insights into the creation of disease-specific, phenotype-specific, and even gene-specific predictors of pathogenicity, further advancing our understanding of specific fields.
    Keywords:  Genetics; Machine learning; Pathogenicity predictor; Primary mitochondrial disease; Variant
    DOI:  https://doi.org/10.1186/s40246-023-00557-6
  3. Eur J Clin Invest. 2023 Dec 01. e14138
    Metabolic control of mitophagy.
    Andreas Zimmermann, Frank Madeo, Abhinav Diwan, Junichi Sadoshima, Simon Sedej, Guido Kroemer, Mahmoud Abdellatif.
      Mitochondrial dysfunction is a major hallmark of ageing and related chronic disorders. Controlled removal of damaged mitochondria by the autophagic machinery, a process known as mitophagy, is vital for mitochondrial homeostasis and cell survival. The central role of mitochondria in cellular metabolism places mitochondrial removal at the interface of key metabolic pathways affecting the biosynthesis or catabolism of acetyl-coenzyme A, nicotinamide adenine dinucleotide, polyamines, as well as fatty acids and amino acids. Molecular switches that integrate the metabolic status of the cell, like AMP-dependent protein kinase, protein kinase A, mechanistic target of rapamycin and sirtuins, have also emerged as important regulators of mitophagy. In this review, we discuss how metabolic regulation intersects with mitophagy. We place special emphasis on the metabolic regulatory circuits that may be therapeutically targeted to delay ageing and mitochondria-associated chronic diseases. Moreover, we identify outstanding knowledge gaps, such as the ill-defined distinction between basal and damage-induced mitophagy, which must be resolved to boost progress in this area.
    Keywords:  AMPK; NAD; acetyl-CoA; ageing; ageing-related disease; metabolism; mitophagy; spermidine
    DOI:  https://doi.org/10.1111/eci.14138
  4. J Physiol. 2023 Nov 28.
    Loss of mitochondrial Ca2+ uptake protein 3 impairs skeletal muscle calcium handling and exercise capacity.
    Barbara Roman, Yusuf Mastoor, Yingfan Zhang, Dennis Gross, Danielle Springer, Chengyu Liu, Brian Glancy, Elizabeth Murphy.
      Mitochondrial calcium concentration ([Ca2+ ]m ) plays an essential role in bioenergetics, and loss of [Ca2+ ]m homeostasis can trigger diseases and cell death in numerous cell types. Ca2+ uptake into mitochondria occurs via the mitochondrial Ca2+ uniporter (MCU), which is regulated by three mitochondrial Ca2+ uptake (MICU) proteins localized in the intermembrane space, MICU1, 2, and 3. We generated a mouse model of systemic MICU3 ablation and examined its physiological role in skeletal muscle. We found that loss of MICU3 led to impaired exercise capacity. When the muscles were directly stimulated there was a decrease in time to fatigue. MICU3 ablation significantly increased the maximal force of the KO muscle and altered fibre type composition with an increase in the ratio of type IIb (low oxidative capacity) to type IIa (high oxidative capacity) fibres. Furthermore, MICU3-KO mitochondria have reduced uptake of Ca2+ and increased phosphorylation of pyruvate dehydrogenase, indicating that KO animals contain less Ca2+ in their mitochondria. Skeletal muscle from MICU3-KO mice exhibited lower net oxidation of NADH during electrically stimulated muscle contraction compared with wild-type. These data demonstrate that MICU3 plays a role in skeletal muscle physiology by setting the proper threshold for mitochondrial Ca2+ uptake, which is important for matching energy demand and supply in muscle. KEY POINTS: Mitochondrial calcium uptake is an important regulator of bioenergetics and cell death and is regulated by the mitochondrial calcium uniporter (MCU) and three calcium sensitive regulatory proteins (MICU1, 2 and 3). Loss of MICU3 leads to impaired exercise capacity and decreased time to skeletal muscle fatigue. Skeletal muscle from MICU3-KO mice exhibits a net oxidation of NADH during electrically stimulated muscle contractions, suggesting that MICU3 plays a role in skeletal muscle physiology by matching energy demand and supply.
    Keywords:  MICU3; calcium uptake; skeletal muscle
    DOI:  https://doi.org/10.1113/JP284894
  5. Nat Metab. 2023 Nov 30.
    Efficient elimination of MELAS-associated m.3243G mutant mitochondrial DNA by an engineered mitoARCUS nuclease.
    Wendy K Shoop, Janel Lape, Megan Trum, Alea Powell, Emma Sevigny, Adam Mischler, Sandra R Bacman, Flavia Fontanesi, Jeff Smith, Derek Jantz, Cassandra L Gorsuch, Carlos T Moraes.
      Nuclease-mediated editing of heteroplasmic mitochondrial DNA (mtDNA) seeks to preferentially cleave and eliminate mutant mtDNA, leaving wild-type genomes to repopulate the cell and shift mtDNA heteroplasmy. Various technologies are available, but many suffer from limitations based on size and/or specificity. The use of ARCUS nucleases, derived from naturally occurring I-CreI, avoids these pitfalls due to their small size, single-component protein structure and high specificity resulting from a robust protein-engineering process. Here we describe the development of a mitochondrial-targeted ARCUS (mitoARCUS) nuclease designed to target one of the most common pathogenic mtDNA mutations, m.3243A>G. mitoARCUS robustly eliminated mutant mtDNA without cutting wild-type mtDNA, allowing for shifts in heteroplasmy and concomitant improvements in mitochondrial protein steady-state levels and respiration. In vivo efficacy was demonstrated using a m.3243A>G xenograft mouse model with mitoARCUS delivered systemically by adeno-associated virus. Together, these data support the development of mitoARCUS as an in vivo gene-editing therapeutic for m.3243A>G-associated diseases.
    DOI:  https://doi.org/10.1038/s42255-023-00932-6
  6. Trends Genet. 2023 Nov 29. pii: S0168-9525(23)00257-3. [Epub ahead of print]
    TFAM mislocalization during spermatogenesis.
    Sam Kavoosi, Martin Picard, Brett A Kaufman.
      Mitochondrial DNA (mtDNA) is inherited almost exclusively from the maternal lineage. Paternal destruction of either mtDNA or whole mitochondria has been the dominant model for mtDNA transmission. Recently, Lee et al. provided evidence for mitochondrial transcription factor A (TFAM) import sequence regulation as a potential cause for mtDNA depletion in human sperm before fertilization.
    Keywords:  TFAM; mtDNA; spermatogenesis; uniparental inheritance
    DOI:  https://doi.org/10.1016/j.tig.2023.11.002
  7. Mol Neurobiol. 2023 Nov 28.
    Multifaceted Roles of AFG3L2, a Mitochondrial ATPase in Relation to Neurological Disorders.
    Ranita Ghosh Dastidar, Saradindu Banerjee, Piyush Behari Lal, Somasish Ghosh Dastidar.
      AFG3L2 is a zinc metalloprotease and an ATPase localized in an inner mitochondrial membrane involved in mitochondrial quality control of several nuclear- and mitochondrial-encoded proteins. Mutations in AFG3L2 lead to diseases like slow progressive ataxia, which is a neurological disorder. This review delineates the cellular functions of AFG3L2 and its dysfunction that leads to major clinical outcomes, which include spinocerebellar ataxia type 28, spastic ataxia type 5, and optic atrophy type 12. It summarizes all relevant AFG3L2 mutations associated with the clinical outcomes to understand the detailed mechanisms attributable to its structure-related multifaceted roles in proteostasis and quality control. We face early diagnostic challenges of ataxia and optic neuropathy due to asymptomatic parents and variable clinical manifestations due to heterozygosity/homozygosity of AFG3L2 mutations. This review intends to promote AFG3L2 as a putative prognostic or diagnostic marker. Functions, mutations, and clinical manifestations in AFG3L2, a mitochondrial AAA + ATPases.
    Keywords:  AFG3L2; Ataxia; Mitochondria; Neurological disorders; SCA28; Zinc metalloprotease
    DOI:  https://doi.org/10.1007/s12035-023-03768-z
  8. J Biochem. 2023 Nov 28. pii: mvad098. [Epub ahead of print]
    Review title: Mechanisms of mitochondrial reorganization.
    Tatsuro Maruyama, Yutaro Hama, Nobuo N Noda.
      The cytoplasm of eukaryotes is dynamically zoned by membrane-bound and membraneless organelles. Cytoplasmic zoning allows various biochemical reactions to take place at the right time and place. Mitochondrion is a membrane-bound organelle that provides a zone for intracellular energy production and metabolism of lipids and iron. A key feature of mitochondria is their high dynamics: mitochondria constantly undergo fusion and fission, and excess or damaged mitochondria are selectively eliminated by mitophagy. Therefore, mitochondria are appropriate model systems to understand dynamic cytoplasmic zoning by membrane organelles. In this review, we summarize the molecular mechanisms of mitochondrial fusion and fission as well as mitophagy unveiled through studies using yeast and mammalian models.
    Keywords:  cytoplasmic zoning; mitochondria; mitochondrial fission; mitochondrial fusion; mitophagy
    DOI:  https://doi.org/10.1093/jb/mvad098
  9. Cell Mol Life Sci. 2023 Nov 25. 80(12): 373
    Combined RNA interference and gene replacement therapy targeting MFN2 as proof of principle for the treatment of Charcot-Marie-Tooth type 2A.
    Federica Rizzo, Silvia Bono, Marc David Ruepp, Sabrina Salani, Linda Ottoboni, Elena Abati, Valentina Melzi, Chiara Cordiglieri, Serena Pagliarani, Roberta De Gioia, Alessia Anastasia, Michela Taiana, Manuela Garbellini, Simona Lodato, Paolo Kunderfranco, Daniele Cazzato, Daniele Cartelli, Caterina Lonati, Nereo Bresolin, Giacomo Comi, Monica Nizzardo, Stefania Corti.
      Mitofusin-2 (MFN2) is an outer mitochondrial membrane protein essential for mitochondrial networking in most cells. Autosomal dominant mutations in the MFN2 gene cause Charcot-Marie-Tooth type 2A disease (CMT2A), a severe and disabling sensory-motor neuropathy that impacts the entire nervous system. Here, we propose a novel therapeutic strategy tailored to correcting the root genetic defect of CMT2A. Though mutant and wild-type MFN2 mRNA are inhibited by RNA interference (RNAi), the wild-type protein is restored by overexpressing cDNA encoding functional MFN2 modified to be resistant to RNAi. We tested this strategy in CMT2A patient-specific human induced pluripotent stem cell (iPSC)-differentiated motor neurons (MNs), demonstrating the correct silencing of endogenous MFN2 and replacement with an exogenous copy of the functional wild-type gene. This approach significantly rescues the CMT2A MN phenotype in vitro, stabilizing the altered axonal mitochondrial distribution and correcting abnormal mitophagic processes. The MFN2 molecular correction was also properly confirmed in vivo in the MitoCharc1 CMT2A transgenic mouse model after cerebrospinal fluid (CSF) delivery of the constructs into newborn mice using adeno-associated virus 9 (AAV9). Altogether, our data support the feasibility of a combined RNAi and gene therapy strategy for treating the broad spectrum of human diseases associated with MFN2 mutations.
    Keywords:  CMT2A; Gene therapy; MFN2; MitoCharc1; Motor neuron; RNA interfering
    DOI:  https://doi.org/10.1007/s00018-023-05018-w
  10. STAR Protoc. 2023 Nov 29. pii: S2666-1667(23)00712-8. [Epub ahead of print]4(4): 102745
    Protocol for evaluating mitochondrial morphology changes in response to CCCP-induced stress through open-source image processing software.
    Sudeshna Nag, Kaitlin Szederkenyi, Christopher M Yip, G Angus McQuibban.
      Mitochondrial morphology is an indicator of cellular health and function; however, its quantification and categorization into different subclasses is a complicated process. Here, we present a protocol for mitochondrial morphology quantification in the presence and absence of carbonyl cyanide m-chlorophenyl hydrazone stress. We describe steps for the preparation of cells for immunofluorescence microscopy, staining, and morphology quantification. The quantification protocol generates an aspect ratio that helps to categorize mitochondria into two clear subclasses. For complete details on the use and execution of this protocol, please refer to Nag et al.1.
    Keywords:  Cell Biology; Cell culture; Metabolism; Microscopy; Molecular/Chemical Probes
    DOI:  https://doi.org/10.1016/j.xpro.2023.102745
  11. bioRxiv. 2023 Nov 16. pii: 2023.11.15.567241. [Epub ahead of print]
    Mitochondria possess a large, non-selective ionic current that is enhanced during cardiac injury.
    Enrique Balderas, Sandra H J Lee, Thirupura S Shankar, Xue Yin, Anthony M Balynas, Christos P Kyriakopoulos, Craig H Selzman, Stavros G Drakos, Dipayan Chaudhuri.
      Mitochondrial ion channels are essential for energy production and cell survival. To avoid depleting the electrochemical gradient used for ATP synthesis, channels so far described in the mitochondrial inner membrane open only briefly, are highly ion-selective, have restricted tissue distributions, or have small currents. Here, we identify a mitochondrial inner membrane conductance that has strikingly different behavior from previously described channels. It is expressed ubiquitously, and transports cations non-selectively, producing a large, up to nanoampere-level, current. The channel does not lead to inner membrane uncoupling during normal physiology because it only becomes active at depolarized voltages. It is inhibited by external Ca 2+ , corresponding to the intermembrane space, as well as amiloride. This large, ubiquitous, non-selective, amiloride-sensitive (LUNA) current appears most active when expression of the mitochondrial calcium uniporter is minimal, such as in the heart. In this organ, we find that LUNA current magnitude increases two- to threefold in multiple mouse models of injury, an effect also seen in cardiac mitochondria from human patients with heart failure with reduced ejection fraction. Taken together, these features lead us to speculate that LUNA current may arise from an essential protein that acts as a transporter under physiological conditions, but becomes a channel under conditions of mitochondrial stress and depolarization.
    DOI:  https://doi.org/10.1101/2023.11.15.567241
  12. Am J Physiol Cell Physiol. 2023 Nov 27.
    Mitochondrial Transformation of Smooth Muscle Phenotype.
    William J Pearce.
      Smooth muscle cells transition reversibly between contractile and non-contractile phenotypes in response to diverse influences, including many from mitochondria. Numerous molecules including myocardin, pro-contractile miRNAs, and the mitochondrial protein Prohibitin-2 promote contractile differentiation; this is opposed by mitochondrial reactive oxygen species (mtROS), high lactate concentrations, and metabolic reprogramming induced by mitophagy and/or mitochondrial fission. A major pathway through which vascular pathologies such as oncogenic transformation, pulmonary hypertension, and atherosclerosis cause loss of vascular contractility is by enhancing mitophagy and mitochondrial fission with secondary effects on smooth muscle phenotype. Pro-proliferative miRNAs and the mitochondrial translocase TOMM40 also attenuate contractile differentiation. Hypoxia can initiate loss of contractility by enhancing mtROS and lactate production while simultaneously depressing mitochondrial respiration. Mitochondria can reduce cytosolic calcium by moving it across the inner mitochondrial membrane via the Mitochondrial Calcium Uniporter, and then through Mitochondria Associated Membranes to and from calcium stores in the sarcoplasmic/endoplasmic reticulum. Through these effects on calcium, mitochondria can influence multiple calcium-sensitive nuclear transcription factors and genes, some of which govern smooth muscle phenotype, and possibly also the production of genomically encoded mitochondrial proteins and miRNAs (mitoMirs) that target the mitochondria. In turn, mitochondria also can influence nuclear transcription and mRNA processing through Mitochondrial Retrograde Signaling, which is currently a topic of intensive investigation. Mitochondria also can signal to adjacent cells by contribution to the content of exosomes. Considering these and other mechanisms, it is becoming increasingly clear that mitochondria contribute significantly to regulation of smooth muscle phenotype and differentiation.
    Keywords:  Metabolic Reprogramming; Mitochondria Associated Membranes; Mitochondrial Calcium; Mitochondrial Retrograde Signaling; Mitomirs
    DOI:  https://doi.org/10.1152/ajpcell.00354.2023
  13. Cell Death Dis. 2023 Dec 01. 14(12): 788
    Mitochondrial E3 ligase MARCH5 is a safeguard against DNA-PKcs-mediated immune signaling in mitochondria-damaged cells.
    June Heo, Yeon-Ji Park, Yonghyeon Kim, Ho-Soo Lee, Jeongah Kim, Soon-Hwan Kwon, Myeong-Gyun Kang, Hyun-Woo Rhee, Woong Sun, Jae-Ho Lee, Hyeseong Cho.
      Mitochondrial dysfunction is important in various chronic degenerative disorders, and aberrant immune responses elicited by cytoplasmic mitochondrial DNA (mtDNA) may be related. Here, we developed mtDNA-targeted MTERF1-FokI and TFAM-FokI endonuclease systems to induce mitochondrial DNA double-strand breaks (mtDSBs). In these cells, the mtDNA copy number was significantly reduced upon mtDSB induction. Interestingly, in cGAS knockout cells, synthesis of interferon β1 and interferon-stimulated gene was increased upon mtDSB induction. We found that mtDSBs activated DNA-PKcs and HSPA8 in a VDAC1-dependent manner. Importantly, the mitochondrial E3 ligase MARCH5 bound active DNA-PKcs in cells with mtDSBs and reduced the type І interferon response through the degradation of DNA-PKcs. Likewise, mitochondrial damage caused by LPS treatment in RAW264.7 macrophage cells increased phospho-HSPA8 levels and the synthesis of mIFNB1 mRNA in a DNA-PKcs-dependent manner. Accordingly, in March5 knockout macrophages, phospho-HSPA8 levels and the synthesis of mIFNB1 mRNA were prolonged after LPS stimulation. Together, cytoplasmic mtDNA elicits a cellular immune response through DNA-PKcs, and mitochondrial MARCH5 may be a safeguard to prevent persistent inflammatory reactions.
    DOI:  https://doi.org/10.1038/s41419-023-06315-9
  14. Neurol Genet. 2023 Dec;9(6): e200100
    Ataxia Syndrome With Hearing Loss and Nephronophthisis Associated With a Novel Homozygous Variant in XPNPEP3.
    Ilan Ben-Shabat, Malin Kvarnung, Wolfgang Sperker, Helene Bruhn, Anna Wredenberg, Rolf Wibom, Inger Nennesmo, Martin Engvall, Martin Paucar.
       Objectives: Biallelic variants in XPNPEP3 are associated with a rare mitochondrial syndrome characterized by nephronophthisis leading to kidney failure, essential tremor, hearing loss, seizures, and intellectual disability. Only 2 publications on this condition are available. We report a man with a complex ataxia syndrome, hearing loss, and kidney failure associated with a new biallelic variant in XPNPEP3.
    Methods: Clinical evaluation, neuroimaging studies, a kidney biopsy, and whole genome sequencing (WGS) were applied. Since the phenotype was compatible with a mitochondrial disease, a muscle biopsy with morphological and mitochondrial biochemical investigations was performed.
    Results: Axial ataxia, cerebellar atrophy, hearing loss, myopathy, ptosis, supranuclear palsy, and kidney failure because of nephronophthisis were the prominent features in this case. WGS revealed the novel biallelic variant c.766C>T (p.Gln256*) in XPNPEP3. A muscle biopsy revealed COX negative fibers, a few ragged red fibers, and ultrastructural mitochondrial changes. Enzyme activity in respiratory chain complex IV was reduced in muscle and fibroblasts.
    Discussion: This is the first report of a slowly progressive cerebellar ataxia associated with a novel biallelic variant in XPNPEP3. Abnormalities typical for mitochondrial disease and the slow progression of kidney disease are also striking. Our report expands the spectrum of XPNPEP3-related diseases.
    DOI:  https://doi.org/10.1212/NXG.0000000000200100
  15. PLoS Comput Biol. 2023 Nov 27. 19(11): e1011588
    Biased placement of Mitochondria fission facilitates asymmetric inheritance of protein aggregates during yeast cell division.
    Gordon Sun, Christine Hwang, Tony Jung, Jian Liu, Rong Li.
      Mitochondria are essential and dynamic eukaryotic organelles that must be inherited during cell division. In yeast, mitochondria are inherited asymmetrically based on quality, which is thought to be vital for maintaining a rejuvenated cell population; however, the mechanisms underlying mitochondrial remodeling and segregation during this process are not understood. We used high spatiotemporal imaging to quantify the key aspects of mitochondrial dynamics, including motility, fission, and fusion characteristics, upon aggregation of misfolded proteins in the mitochondrial matrix. Using these measured parameters, we developed an agent-based stochastic model of dynamics of mitochondrial inheritance. Our model predicts that biased mitochondrial fission near the protein aggregates facilitates the clustering of protein aggregates in the mitochondrial matrix, and this process underlies asymmetric mitochondria inheritance. These predictions are supported by live-cell imaging experiments where mitochondrial fission was perturbed. Our findings therefore uncover an unexpected role of mitochondrial dynamics in asymmetric mitochondrial inheritance.
    DOI:  https://doi.org/10.1371/journal.pcbi.1011588
  16. J Chin Med Assoc. 2023 Nov 28.
    Leber's hereditary optic neuropathy: Update on the novel genes and therapeutic options.
    Jui-Lin Hu, Chih-Chien Hsu, Yu-Jer Hsiao, Yi-Ying Lin, Wei-Yi Lai, Yu-Hao Liu, Chia-Lin Wang, Yu-Ling Ko, Ming-Long Tsai, Huan-Chin Tseng, Yueh Chien, Yi-Ping Yang.
      A maternal inheritance disorder called Leber's hereditary optic neuropathy (LHON) is the most common primary mitochondrial DNA disorder. In most studies, there are more male patients than female patients, which contradicts the usual pattern in mitochondrial hereditary diseases. This suggests that nuclear DNA (nDNA) may influence the degeneration of retinal ganglion cells (RGCs) in LHON. The primary cause of this is dysfunction in complex I of the electron transport chain, leading to ineffective ATP production. In addition to MT-ND4 or MT-ND1 mutations, genes such as PRICKLE3, YARS2, and DNAJC30, which come from nuclear DNA, also play a role in LHON. These three genes affect the electron chain transport differently. PRICKLE3 interacts with ATP synthase (complex V) at Xp11.23, while YARS2 is a tyrosyl-tRNA synthetase 2 involved in mitochondria. DNAJC30 mutations result in autosomal recessive LHON (arLHON). Understanding how genes impact the disease is crucial for developing new treatments. Idebenone has been approved for treating LHON and has shown safety and efficacy in clinical trials. Mesenchymal stem cell-based therapy has also emerged as a potential treatment for LHON by transferring mitochondria into target cells. Gene therapy research focuses on specific gene mutations, and the wild-type ND4 gene target in the AAV vector has shown promise in clinical trials as a potential treatment for LHON.
    DOI:  https://doi.org/10.1097/JCMA.0000000000001031
  17. Biochem Biophys Res Commun. 2023 Nov 18. pii: S0006-291X(23)01340-2. [Epub ahead of print]691 149246
    Altered anterograde axonal transport of mitochondria in cultured striatal neurons of a knock-in mouse model of Huntington's disease.
    Chao Wu, Haoran Yin, Songdi Fu, Hanna Yoo, Min Zhang, Hyokeun Park.
      Huntington's disease (HD) is a progressive genetic neurodegenerative disease caused by an abnormal expansion of a cytosine-adenine-guanine trinucleotide repeat in the huntingtin gene. One pathological feature of HD is neuronal loss in the striatum. Despite many efforts, mechanisms underlying neuronal loss in HD striatum remain elusive. It was suggested that the mutant huntingtin protein interacts mitochondrial proteins and causes mitochondrial dysfunction in striatal neurons. However, whether axonal transport of mitochondria is altered in HD striatal neurons remains controversial. Here, we examined axonal transport of single mitochondria labelled with Mito-DsRed2 in cultured striatal neurons of zQ175 knock-in mice (a knock-in mouse model of HD). We observed decreased anterograde axonal transport of proximal mitochondria in HD striatal neurons compared with wild-type (WT) striatal neurons. Decreased anterograde transport in HD striatal neurons was prevented by overexpressing mitochondrial Rho GTPase 1 (Miro1). Our results offer a new insight into mechanisms underlying neuronal loss in the striatum in HD.
    Keywords:  Axonal transport; Huntington's disease; Miro1; Mitochondria; Neurodegenerative disease; Real-time imaging
    DOI:  https://doi.org/10.1016/j.bbrc.2023.149246
  18. J Lasers Med Sci. 2023 ;14 e41
    The Effect of Photobiomodulation on the Treatment of Hereditary Mitochondrial Diseases.
    Richard Baskerville, Nykle Krijgsveld, Patrick Esser, Glen Jeffery, Joanna Poulton.
      Introduction: Despite a wide variety of clinical presentations in hereditary Mitochondrial Diseases, muscle fatigue is a common theme and impairs a patient's quality of life and ability to function. Current treatments are only supportive and include nutritional supplementation and physical therapy. Photobiomodulation therapy (PBMT) using low-intensity, narrow spectrum light in the red/near infrared (NIR) range, from a low-level laser or light-emitting diode sources, enhances mitochondrial function in preclinical and clinical studies on a range of conditions. However, little research has been done on the effectiveness of photobiomodulation in hereditary mitochondrial disorders. Methods: We performed a scoping review of the evidence of the beneficial effects of photobiomodulation for treating the muscle-related symptoms of hereditary mitochondrial disease. Results: No studies regarding photobiomodulation in hereditary mitochondrial disease were identified. However, in other clinical conditions featuring acquired mitochondrial impairment, we identified studies that suggested improved function, although sample sizes were small in number and statistical power. Conclusion: There is emerging evidence of efficacy for PBMT for diseases involving acquired mitochondrial insufficiency. We identified no published research on PBMT in hereditary mitochondrial disease, but this review confirms a theoretical rationale for a positive effect and suggests further research.
    Keywords:  Cytochrome oxidase; Fatigue; Mitochondrial disease; Muscle; Near-infrared; Photobiomodulation
    DOI:  https://doi.org/10.34172/jlms.2023.41
  19. Mol Ther Methods Clin Dev. 2023 Dec 14. 31 101152
    Mitochondrial transplantation reduces lower limb ischemia-reperfusion injury by increasing skeletal muscle energy and adipocyte browning.
    Jiaqi Zeng, Jianing Liu, Haiya Ni, Ling Zhang, Jun Wang, Yazhou Li, Wentao Jiang, Ziyu Wu, Min Zhou.
      Recent studies have shown that mitochondrial transplantation can repair lower limb IRI, but the underlying mechanism of the repair effect remains unclear. In this study, we found that in addition to being taken up by skeletal muscle cells, human umbilical cord mesenchymal stem cells (hMSCs)-derived mitochondria were also taken up by adipocytes, which was accompanied by an increase in optic atrophy 1 (OPA1) and uncoupling protein 1. Transplantation of hMSCs-derived mitochondria could not only supplement the original damaged mitochondrial function of skeletal muscle, but also promote adipocyte browning by increasing the expression of OPA1. In this process, mitochondrial transplantation can reduce cell apoptosis and repair muscle tissue, which promotes the recovery of motor function in vivo. To the best of our knowledge, there is no study on the therapeutic mechanism of mitochondrial transplantation from this perspective, which could provide a theoretical basis.
    Keywords:  Mitochondrial damage; adipocyte browning; lower limb ischemia-reperfusion injury; mesenchymal stem cells; mitochondrial transplantation
    DOI:  https://doi.org/10.1016/j.omtm.2023.101152
  20. Nat Metab. 2023 Nov 30.
    Mitophagy in human health, ageing and disease.
    Anna Picca, Julie Faitg, Johan Auwerx, Luigi Ferrucci, Davide D'Amico.
      Maintaining optimal mitochondrial function is a feature of health. Mitophagy removes and recycles damaged mitochondria and regulates the biogenesis of new, fully functional ones preserving healthy mitochondrial functions and activities. Preclinical and clinical studies have shown that impaired mitophagy negatively affects cellular health and contributes to age-related chronic diseases. Strategies to boost mitophagy have been successfully tested in model organisms, and, recently, some have been translated into clinics. In this Review, we describe the basic mechanisms of mitophagy and how mitophagy can be assessed in human blood, the immune system and tissues, including muscle, brain and liver. We outline mitophagy's role in specific diseases and describe mitophagy-activating approaches successfully tested in humans, including exercise and nutritional and pharmacological interventions. We describe how mitophagy is connected to other features of ageing through general mechanisms such as inflammation and oxidative stress and forecast how strengthening research on mitophagy and mitophagy interventions may strongly support human health.
    DOI:  https://doi.org/10.1038/s42255-023-00930-8
  21. Am J Physiol Heart Circ Physiol. 2023 Dec 01.
    Cardiovascular Aging: Spotlight on Mitochondria.
    Md Akkas Ali, Rachel Gioscia-Ryan, Dongli Yang, Nadia R Sutton, Daniel J Tyrrell.
      Mitochondria are cellular organelles critical for ATP production and are particularly relevant to cardiovascular diseases including heart failure, atherosclerosis, ischemia reperfusion injury, and cardiomyopathies. With advancing age, even in the absence of clinical disease, mitochondrial homeostasis becomes disrupted (e.g. redox balance, mitochondrial DNA damage, oxidative metabolism, and mitochondrial quality control). Mitochondrial dysregulation leads to the accumulation of damaged and dysfunctional mitochondria, producing excessive reactive oxygen species and perpetuating mitochondrial dysfunction. Additionally, mitochondrial DNA, cardiolipin, and N-formyl peptides are potent activators of cell-intrinsic and extrinsic inflammatory pathways. These age-related mitochondrial changes contribute to development of cardiovascular diseases. This review covers the impact of aging on mitochondria and links these mechanisms to therapeutic implications for age-associated cardiovascular diseases.
    Keywords:  Cardiovascular; aging; metabolism; mitochondria; senescence
    DOI:  https://doi.org/10.1152/ajpheart.00632.2023
  22. Biochemistry. 2023 Dec 01.
    Substrate Sequestration and Chain Flipping in Human Mitochondrial Acyl Carrier Protein.
    Yixing Suo, Aochiu Chen, James J La Clair, Michael D Burkart.
      Outside of their involvement in energy production, mitochondria play a critical role for the cell through their access to a discrete pathway for fatty acid biosynthesis. Despite decades of study in bacterial fatty acid synthases (the putative evolutionary mitochondrial precursor), our understanding of human mitochondrial fatty acid biosynthesis remains incomplete. In particular, the role of the key carrier protein, human mitochondrial acyl carrier protein (mACP), which shuttles the substrate intermediates through the pathway, has not been well-studied in part due to challenges in protein expression and purification. Herein, we report a reliable method for recombinant Escherichia coli expression and purification of mACP. Fundamental characteristics, including substrate sequestration and chain-flipping activity, are demonstrated in mACP using solvatochromic response. This study provides an efficient approach toward understanding the fundamental protein-protein interactions of mACP and its partner proteins, ultimately leading to a molecular understanding of human mitochondrial diseases such as mitochondrial fatty acid oxidation deficiencies.
    DOI:  https://doi.org/10.1021/acs.biochem.3c00447
  23. Pharmacol Res. 2023 Nov 25. pii: S1043-6618(23)00374-2. [Epub ahead of print]199 107018
    Powering prescription: Mitochondria as "Living Drugs" - Definition, clinical applications, and industry advancements.
    Andrés Caicedo, Emilia Morales, Aldana Moyano, Sebastian Peñaherrera, José Peña-Cisneros, Abigail Benavides-Almeida, Álvaro A Pérez-Meza, Alissen Haro-Vinueza, Cristina Ruiz, Paola Robayo, Doménica Tenesaca, Diego Barba, Kevin Zambrano, Verónica Castañeda, Keshav K Singh.
      Mitochondria's role as engines and beacons of metabolism and determinants of cellular health is being redefined through their therapeutic application as "Living Drugs" (LDs). Artificial mitochondrial transfer/transplant (AMT/T), encompassing various techniques to modify, enrich, or restore mitochondria in cells and tissues, is revolutionizing acellular therapies and the future of medicine. This article proposes a necessary definition for LDs within the Advanced Therapeutic Medicinal Products (ATMPs) framework. While recognizing different types of LDs as ATMPs, such as mesenchymal stem cells (MSCs) and chimeric antigen receptor T (CAR T) cells, we focus on mitochondria due to their unique attributes that distinguish them from traditional cell therapies. These attributes include their inherent living nature, diverse sources, industry applicability, validation, customizability for therapeutic needs, and their capability to adapt and respond within recipient cells. We trace the journey from initial breakthroughs in AMT/T to the current state-of-the-art applications by emerging innovative companies, highlighting the need for manufacturing standards to navigate the transition of mitochondrial therapies from concept to clinical practice. By providing a comprehensive overview of the scientific, clinical, and commercial landscape of mitochondria as LDs, this article contributes to the essential dialogue among regulatory agencies, academia, and industry to shape their future in medicine.
    Keywords:  Acellular therapy; Advanced therapeutic medicinal products (ATMPs); Artificial mitochondrial transfer transplant (AMT/T); Cell therapy; Industry; Innovation; Living drugs (LDs); Mitochondria
    DOI:  https://doi.org/10.1016/j.phrs.2023.107018
  24. J Physiol. 2023 Nov 27.
    Targeting mitochondrial Ca2+ uptake for the treatment of amyotrophic lateral sclerosis.
    Renjia Zhong, Michael T Rua, Lan Wei-LaPierre.
      Amyotrophic lateral sclerosis (ALS) is a rare adult-onset neurodegenerative disease characterized by progressive motor neuron (MN) loss, muscle denervation and paralysis. Over the past several decades, researchers have made tremendous efforts to understand the pathogenic mechanisms underpinning ALS, with much yet to be resolved. ALS is described as a non-cell autonomous condition with pathology detected in both MNs and non-neuronal cells, such as glial cells and skeletal muscle. Studies in ALS patient and animal models reveal ubiquitous abnormalities in mitochondrial structure and function, and disturbance of intracellular calcium homeostasis in various tissue types, suggesting a pivotal role of aberrant mitochondrial calcium uptake and dysfunctional calcium signalling cascades in ALS pathogenesis. Calcium signalling and mitochondrial dysfunction are intricately related to the manifestation of cell death contributing to MN loss and skeletal muscle dysfunction. In this review, we discuss the potential contribution of intracellular calcium signalling, particularly mitochondrial calcium uptake, in ALS pathogenesis. Functional consequences of excessive mitochondrial calcium uptake and possible therapeutic strategies targeting mitochondrial calcium uptake or the mitochondrial calcium uniporter, the main channel mediating mitochondrial calcium influx, are also discussed.
    Keywords:  ALS; mitochondria calcium; motor neuron; skeletal muscle; therapeutic target
    DOI:  https://doi.org/10.1113/JP284143
  25. Neuromuscul Disord. 2023 Nov 04. pii: S0960-8966(23)00774-5. [Epub ahead of print]
    A new family with a case of severe early-onset muscle fatigue and a peculiar maternally inherited painful swelling in chewing muscles associated with homoplasmic m.15992A>T mutation in mitochondrial tRNAPro.
    Elena Ghirigato, Francesca Terenzi, Mirko Baglivo, Nadia Zanetti, Francesco Baldo, Flora Maria Murru, Marco Bobbo, Egidio Barbi, Massimo Zeviani, Irene Bruno, Eleonora Lamantea.
      A 16-year-old boy was evaluated for a history of exercise-induced fatigability associated with nausea even after minimal effort, lower limbs muscle hypotrophy, and swelling of the masseter muscles after chewing. Laboratory tests were remarkable for hyperlactatemia and metabolic acidosis after short physical activity. The muscle biopsy showed non-specific mitochondrial alterations and an increase in intrafibral lipids. Biochemical analysis showed reduced activity of the respiratory chain complexes. Mitochondrial DNA sequencing revealed the presence of a homoplasmic variant m.15992A>T in the MT-TP gene, coding for the mt-tRNAPro in the patient, in his mother and in his brother. Pathogenic or likely pathogenic variants in MT-TP gene are rare. They are responsible for different clinical presentation, almost ever involving the muscle tissue. We report the first family with exercise-induced muscle weakness and swelling of the chewing muscles due to m.15992A>T variant in absence of J1c10 haplogroup, confirming its pathogenicity.
    Keywords:  MT-TP; Masseter muscle swelling; Mitochondrial myopathy; Mitochondrial tRNA
    DOI:  https://doi.org/10.1016/j.nmd.2023.11.001
  26. J Vis Exp. 2023 Nov 10.
    Analyzing Mitochondrial Function in a Drosophila melanogaster PINK1B9-Null Mutant Using High-resolution Respirometry.
    Paula Michelotti, Tâmie Duarte, Cristiane L Dalla Corte.
      Neurodegenerative diseases, including Parkinson's Disease (PD), and cellular disturbances such as cancer are some of the disorders that disrupt energy metabolism with impairment of mitochondrial functions. Mitochondria are organelles that control both energy metabolism and cellular processes involved in cell survival and death. For this reason, approaches to evaluate mitochondrial function can offer important insights into cellular conditions in pathological and physiological processes. In this regard, high-resolution respirometry (HRR) protocols allow evaluation of the whole mitochondrial respiratory chain function or the activity of specific mitochondrial complexes. Furthermore, studying mitochondrial physiology and bioenergetics requires genetically and experimentally tractable models such as Drosophila melanogaster. This model presents several advantages, such as its similarity to human physiology, its rapid life cycle, easy maintenance, cost-effectiveness, high throughput capabilities, and a minimized number of ethical concerns. These attributes collectively establish it as an invaluable tool for dissecting complex cellular processes. The present work explains how to analyze mitochondrial function using the Drosophila melanogaster PINK1B9-null mutant. The pink1 gene is responsible for encoding PTEN-induced putative kinase 1, through a process recognized as mitophagy, which is crucial for the removal of dysfunctional mitochondria from the mitochondrial network. Mutations in this gene have been associated with an autosomal recessive early-onset familial form of PD. This model can be used to study mitochondrial dysfunction involved in the pathophysiology of PD.
    DOI:  https://doi.org/10.3791/65664
  27. Mov Disord. 2023 Nov 25.
    Impaired Mitochondrial Respiration in REM-Sleep Behavior Disorder: A Biomarker of Parkinson's Disease?
    Gerardo Ongari, Cristina Ghezzi, Deborah Di Martino, Antonio Pisani, Michele Terzaghi, Micol Avenali, Enza Maria Valente, Silvia Cerri, Fabio Blandini.
       BACKGROUND: Idiopathic rapid eye movement (REM) sleep behavior disorder (iRBD) is associated with prodromal Parkinson's disease (PD), but the mechanisms linking phenoconversion of iRBD to PD have not yet been clarified. Considering the association between mitochondrial dysfunction and sleep disturbances in PD, we explored mitochondrial activity in fibroblasts derived from iRBD patients to identify a biochemical profile that could mark the presence of impending neurodegeneration.
    METHODS: The study involved 28 participants, divided into three groups: patients diagnosed with iRBD, PD patients converted from iRBD (RBD-PD), and healthy controls. We performed a comprehensive assessment of mitochondrial function, including an examination of mitochondrial morphology, analysis of mitochondrial protein expression levels by western blot, and measurement of mitochondrial respiration using the Seahorse XFe24 analyzer.
    RESULTS: In basal conditions, mitochondrial respiration did not differ between iRBD and control fibroblasts, but when cells were challenged with a higher energy demand, iRBD fibroblasts exhibited a significant (P = 0.006) drop in maximal and spare respiration compared to controls. Interestingly, RBD-PD patients showed the same alterations with a further significant reduction in oxygen consumption linked to adenosine triphosphate production (P = 0.032). Moreover, RBD-PD patients exhibited a significant decrease in protein levels of complexes III (P = 0.02) and V (P = 0.002) compared to controls, along with fragmentation of the mitochondrial network. iRBD patients showed similar, but milder alterations.
    CONCLUSIONS: Altogether, these findings suggest that mitochondrial dysfunctions in individuals with iRBD might predispose to worsening of the bioenergetic profile observed in RBD-PD patients, highlighting these alterations as potential predictors of phenoconversion to PD. © 2023 The Authors. Movement Disorders published by Wiley Periodicals LLC on behalf of International Parkinson and Movement Disorder Society.
    Keywords:  Parkinson's disease; fibroblasts; idiopathic REM sleep disorders; mitochondrial dysfunction; prodromal markers
    DOI:  https://doi.org/10.1002/mds.29643
  28. Front Neurosci. 2023 ;17 1289027
    Skeletal muscle proteome analysis underpins multifaceted mitochondrial dysfunction in Friedreich's ataxia.
    Elisabetta Indelicato, Klaus Faserl, Matthias Amprosi, Wolfgang Nachbauer, Rainer Schneider, Julia Wanschitz, Bettina Sarg, Sylvia Boesch.
      Friedreich's ataxia (FRDA) is a severe multisystemic disorder caused by a deficiency of the mitochondrial protein frataxin. While some aspects of FRDA pathology are developmental, the causes underlying the steady progression are unclear. The inaccessibility of key affected tissues to sampling is a main hurdle. Skeletal muscle displays a disease phenotype and may be sampled in vivo to address open questions on FRDA pathophysiology. Thus, we performed a quantitative mass spectrometry-based proteomics analysis in gastrocnemius skeletal muscle biopsies from genetically confirmed FRDA patients (n = 5) and controls. Obtained data files were processed using Proteome Discoverer and searched by Sequest HT engine against a UniProt human reference proteome database. Comparing skeletal muscle proteomics profiles between FRDA and controls, we identified 228 significant differentially expressed (DE) proteins, of which 227 were downregulated in FRDA. Principal component analysis showed a clear separation between FRDA and control samples. Interactome analysis revealed clustering of DE proteins in oxidative phosphorylation, ribosomal elements, mitochondrial architecture control, and fission/fusion pathways. DE findings in the muscle-specific proteomics suggested a shift toward fast-twitching glycolytic fibers. Notably, most DE proteins (169/228, 74%) are target of the transcription factor nuclear factor-erythroid 2. Our data corroborate a mitochondrial biosignature of FRDA, which extends beyond a mere oxidative phosphorylation failure. Skeletal muscle proteomics highlighted a derangement of mitochondrial architecture and maintenance pathways and a likely adaptive metabolic shift of contractile proteins. The present findings are relevant for the design of future therapeutic strategies and highlight the value of skeletal muscle-omics as disease state readout in FRDA.
    Keywords:  Friedreich’s ataxia; frataxin; mass spectrometry; mitochondria; proteomics; skeletal muscle
    DOI:  https://doi.org/10.3389/fnins.2023.1289027
  29. Front Neurol. 2023 ;14 1277944
    Lowered oxidative capacity in spinal muscular atrophy, Jokela type; comparison with mitochondrial muscle disease.
    Nadja Ratia, Edouard Palu, Hanna Lantto, Emil Ylikallio, Ritva Luukkonen, Anu Suomalainen, Mari Auranen, Päivi Piirilä.
       Introduction: Spinal muscular atrophy, Jokela type (SMAJ) is a rare autosomal dominantly hereditary form of spinal muscular atrophy caused by a point mutation c.197G>T in CHCHD10. CHCHD10 is known to be involved in the regulation of mitochondrial function even though patients with SMAJ do not present with multiorgan symptoms of mitochondrial disease. We aimed to characterize the cardiopulmonary oxidative capacity of subjects with SMAJ compared to healthy controls and patients with mitochondrial myopathy.
    Methods: Eleven patients with genetically verified SMAJ, 26 subjects with mitochondrial myopathy (MM), and 28 healthy volunteers underwent a cardiopulmonary exercise test with lactate and ammonia sampling. The effect of the diagnosis group on the test results was analysed using a linear model.
    Results: Adjusted for sex, age, and BMI, the SMAJ group had lower power output (p < 0.001), maximal oxygen consumption (VO2 max) (p < 0.001), and mechanical efficiency (p < 0.001) compared to the healthy controls but like that in MM. In the SMAJ group and healthy controls, plasma lactate was lower than in MM measured at rest, light exercise, and 30 min after exercise (p ≤ 0.001-0.030) and otherwise lactate in SMAJ was lower than controls and MM, in longitudinal analysis p = 0.018. In MM, the ventilatory equivalent for oxygen was higher (p = 0.040), and the fraction of end-tidal CO2 lower in maximal exercise compared to healthy controls (p = 0.023) and subjects with SMAJ.
    Conclusion: In cardiopulmonary exercise test, subjects with SMAJ showed a similar decrease in power output and oxidative capacity as subjects with mitochondrial myopathy but did not exhibit findings typical of mitochondrial disease.
    Keywords:  cardiopulmonary exercise testing; lactate; mitochondrial myopathy; motoneuron disease; spinal muscular atrophy Jokela type (SMAJ)
    DOI:  https://doi.org/10.3389/fneur.2023.1277944
  30. Cell Rep. 2023 Nov 30. pii: S2211-1247(23)01478-X. [Epub ahead of print]42(12): 113466
    NGLY1 mutations cause protein aggregation in human neurons.
    Andreea Manole, Thomas Wong, Amanda Rhee, Sammy Novak, Shao-Ming Chin, Katya Tsimring, Andres Paucar, April Williams, Traci Fang Newmeyer, Simon T Schafer, Idan Rosh, Susmita Kaushik, Rene Hoffman, Songjie Chen, Guangwen Wang, Michael Snyder, Ana Maria Cuervo, Leo Andrade, Uri Manor, Kevin Lee, Jeffrey R Jones, Shani Stern, Maria C Marchetto, Fred H Gage.
      Biallelic mutations in the gene that encodes the enzyme N-glycanase 1 (NGLY1) cause a rare disease with multi-symptomatic features including developmental delay, intellectual disability, neuropathy, and seizures. NGLY1's activity in human neural cells is currently not well understood. To understand how NGLY1 gene loss leads to the specific phenotypes of NGLY1 deficiency, we employed direct conversion of NGLY1 patient-derived induced pluripotent stem cells (iPSCs) to functional cortical neurons. Transcriptomic, proteomic, and functional studies of iPSC-derived neurons lacking NGLY1 function revealed several major cellular processes that were altered, including protein aggregate-clearing functionality, mitochondrial homeostasis, and synaptic dysfunctions. These phenotypes were rescued by introduction of a functional NGLY1 gene and were observed in iPSC-derived mature neurons but not astrocytes. Finally, laser capture microscopy followed by mass spectrometry provided detailed characterization of the composition of protein aggregates specific to NGLY1-deficient neurons. Future studies will harness this knowledge for therapeutic development.
    Keywords:  CP: Neuroscience; NGLY1 deficiency; chaperones; fragmented mitochondria; neural cells; organoids; protein aggregates
    DOI:  https://doi.org/10.1016/j.celrep.2023.113466
  31. Front Physiol. 2023 ;14 1263420
    Interactions of amyloidogenic proteins with mitochondrial protein import machinery in aging-related neurodegenerative diseases.
    Ashley L Reed, Wayne Mitchell, Andrei T Alexandrescu, Nathan N Alder.
      Most mitochondrial proteins are targeted to the organelle by N-terminal mitochondrial targeting sequences (MTSs, or "presequences") that are recognized by the import machinery and subsequently cleaved to yield the mature protein. MTSs do not have conserved amino acid compositions, but share common physicochemical properties, including the ability to form amphipathic α-helical structures enriched with basic and hydrophobic residues on alternating faces. The lack of strict sequence conservation implies that some polypeptides can be mistargeted to mitochondria, especially under cellular stress. The pathogenic accumulation of proteins within mitochondria is implicated in many aging-related neurodegenerative diseases, including Alzheimer's, Parkinson's, and Huntington's diseases. Mechanistically, these diseases may originate in part from mitochondrial interactions with amyloid-β precursor protein (APP) or its cleavage product amyloid-β (Aβ), α-synuclein (α-syn), and mutant forms of huntingtin (mHtt), respectively, that are mediated in part through their associations with the mitochondrial protein import machinery. Emerging evidence suggests that these amyloidogenic proteins may present cryptic targeting signals that act as MTS mimetics and can be recognized by mitochondrial import receptors and transported into different mitochondrial compartments. Accumulation of these mistargeted proteins could overwhelm the import machinery and its associated quality control mechanisms, thereby contributing to neurological disease progression. Alternatively, the uptake of amyloidogenic proteins into mitochondria may be part of a protein quality control mechanism for clearance of cytotoxic proteins. Here we review the pathomechanisms of these diseases as they relate to mitochondrial protein import and effects on mitochondrial function, what features of APP/Aβ, α-syn and mHtt make them suitable substrates for the import machinery, and how this information can be leveraged for the development of therapeutic interventions.
    Keywords:  amyloids; cryptic targeting; mitochondria; neurodegeneration; protein import; targeting signals
    DOI:  https://doi.org/10.3389/fphys.2023.1263420
  32. Mitochondrion. 2023 Nov 29. pii: S1567-7249(23)00095-8. [Epub ahead of print]
    Role of F-actin-mediated endocytosis and exercise in mitochondrial transplantation in an experimental Parkinson's disease mouse model.
    Rachit Jain, Nusrat Begum, Shruti Rajan, Kamatham Pushpa Tryphena, Dharmendra Kumar Khatri.
      Dopaminergic neurons gradually deteriorate in Parkinson's Disease (PD), which is characterized by the intracellular accumulation of Lewy bodies that are enriched with α-synuclein protein. Mitochondrial dysfunction is one of the primary contributors to this and is considered as the central player in the pathogenesis of PD. Recently, improving mitochondrial function has been extensively explored as a therapeutic strategy in various preclinical PD models. Mitochondrial transplantation is one such naïve yet highly efficient technique that has been well explored in diseases like diabetes, NAFLD, and cardiac ischemia but not in PD. Here, we compared the effects of transplanting normal allogenic mitochondria to those of transplanting exercise-induced allogenic mitochondria isolated from the liver into the PD mouse model. It is already known that normal Mitochondrial Transplant (MT) reduces the PD pathology, but our research found out that exercise-induced mitochondria were more effective in treating the PD pathology because they had higher respiratory capacities. Additionally, compared to a standard transplant, this therapy significantly boosted the rate of mitochondrial biogenesis and the quantity of mitochondrial subunits in PD mice. Further, we also explored the mechanism of mitochondrial uptake into the cells and found that F-actin plays a key role in the internalization of mitochondria. This study is the first to demonstrate the relevance of exercise-induced allogenic MT and the function of F-actin in the internalization of mitochondria in PD mice.
    Keywords:  Exercise; F-actin; Mitochondria; Mitochondrial Transplant; Parkinson’s Disease
    DOI:  https://doi.org/10.1016/j.mito.2023.11.007
  33. Front Cell Dev Biol. 2023 ;11 1290046
    Mitochondrial quality control in health and cardiovascular diseases.
    Asli E Atici, Timothy R Crother, Magali Noval Rivas.
      Cardiovascular diseases (CVDs) are one of the primary causes of mortality worldwide. An optimal mitochondrial function is central to supplying tissues with high energy demand, such as the cardiovascular system. In addition to producing ATP as a power source, mitochondria are also heavily involved in adaptation to environmental stress and fine-tuning tissue functions. Mitochondrial quality control (MQC) through fission, fusion, mitophagy, and biogenesis ensures the clearance of dysfunctional mitochondria and preserves mitochondrial homeostasis in cardiovascular tissues. Furthermore, mitochondria generate reactive oxygen species (ROS), which trigger the production of pro-inflammatory cytokines and regulate cell survival. Mitochondrial dysfunction has been implicated in multiple CVDs, including ischemia-reperfusion (I/R), atherosclerosis, heart failure, cardiac hypertrophy, hypertension, diabetic and genetic cardiomyopathies, and Kawasaki Disease (KD). Thus, MQC is pivotal in promoting cardiovascular health. Here, we outline the mechanisms of MQC and discuss the current literature on mitochondrial adaptation in CVDs.
    Keywords:  ROS; cardiovascular disease; mitobiogenesis; mitochondria; mitochondrial dynamics; mitophagy
    DOI:  https://doi.org/10.3389/fcell.2023.1290046
  34. Nat Commun. 2023 Nov 30. 14(1): 7889
    The poxvirus F17 protein counteracts mitochondrially orchestrated antiviral responses.
    Nathan Meade, Helen K Toreev, Ram P Chakrabarty, Charles R Hesser, Chorong Park, Navdeep S Chandel, Derek Walsh.
      Poxviruses are unusual DNA viruses that replicate in the cytoplasm. To do so, they encode approximately 100 immunomodulatory proteins that counteract cytosolic nucleic acid sensors such as cGAMP synthase (cGAS) along with several other antiviral response pathways. Yet most of these immunomodulators are expressed very early in infection while many are variable host range determinants, and significant gaps remain in our understanding of poxvirus sensing and evasion strategies. Here, we show that after infection is established, subsequent progression of the viral lifecycle is sensed through specific changes to mitochondria that coordinate distinct aspects of the antiviral response. Unlike other viruses that cause extensive mitochondrial damage, poxviruses sustain key mitochondrial functions including membrane potential and respiration while reducing reactive oxygen species that drive inflammation. However, poxvirus replication induces mitochondrial hyperfusion that independently controls the release of mitochondrial DNA (mtDNA) to prime nucleic acid sensors and enables an increase in glycolysis that is necessary to support interferon stimulated gene (ISG) production. To counter this, the poxvirus F17 protein localizes to mitochondria and dysregulates mTOR to simultaneously destabilize cGAS and block increases in glycolysis. Our findings reveal how the poxvirus F17 protein disarms specific mitochondrially orchestrated responses to later stages of poxvirus replication.
    DOI:  https://doi.org/10.1038/s41467-023-43635-y
  35. Cureus. 2023 Oct;15(10): e48017
    Methylmalonyl Coenzyme A (CoA) Epimerase Deficiency, an Ultra-Rare Cause of Isolated Methylmalonic Aciduria With Predominant Neurological Features.
    Rui Diogo, Inês B Rua, Sara Ferreira, Célia Nogueira, Cristina Pereira, Joana Rosmaninho-Salgado, Luísa Diogo.
      Methylmalonyl coenzyme A (CoA) epimerase (MCE) converts D-methylmalonyl-CoA into L-methylmalonyl CoA in the final common degradation pathway of valine, isoleucine, methionine, threonine, odd-chain fatty acids, and cholesterol side chains. Methylmalonyl-CoA epimerase deficiency is an ultra-rare autosomal recessive disorder where methylmalonic acid, methylcitrate, 3-hydroxypropionate, and propionylcarnitine are accumulated. We describe two novel pediatric patients and review the previously reported cases of MCE deficiency. Including our two novel patients, at least 24 cases of MCE deficiency have been described, with a broad clinical spectrum ranging from asymptomatic to severely neurologically impaired patients. Our patients are siblings of Arabic origin who presented with metabolic decompensation with coma and epilepsy during infancy. Methylmalonic aciduria was disclosed, L-methylmalonyl-CoA mutase deficiency was assumed, and they were treated accordingly. When first seen in our country, aged 10 and four years, respectively, both presented severe intellectual disability and spasticity. The younger had an ataxic gait, and the older was wheelchair-ridden. The study of the MMUT, MMAA, MMAB, and MMADHC genes was normal. Subsequently, the pathogenic variant c.139C>T (p.Arg47*) in the MCEE gene was identified in homozygosity in both patients, leading to the diagnosis of MCE deficiency (Online Mendelian Inheritance in Man (OMIM®) 251120, McKusick-Nathans Institute of Genetic Medicine, Johns Hopkins University, MD, USA). Most patients were homozygous for that variant (83% of the alleles). Correct diagnosis allowed treatment adequacy and genetic counseling. Methylmalonyl-CoA epimerase deficiency shares a similar biochemical profile with other rare genetic disorders. Patients present with overlapping clinical features with predominant neurological manifestations; genetic testing is indispensable for diagnosis. We found no association between genotype and biochemical and clinical phenotypes.
    Keywords:  intellectual disability; methylmalonic aciduria; methylmalonyl-coa epimerase; seizures; spasticity
    DOI:  https://doi.org/10.7759/cureus.48017
  36. Eur J Neurol. 2023 Nov 28.
    Long-term prognosis of fatty-acid oxidation disorders in adults: Optimism despite the limited effective therapies available.
    Alice Rouyer, Céline Tard, Anne-Frédérique Dessein, Marco Spinazzi, Anne-Laure Bédat-Millet, Dalia Dimitri-Boulos, Aleksandra Nadaj-Pakleza, Jean-Baptiste Chanson, Guillaume Nicolas, Claire Douillard, Pascal Laforêt.
       INTRODUCTION: Fatty-acid oxidation disorders (FAODs) are recessive genetic diseases.
    MATERIALS AND METHODS: We report here clinical and paraclinical data from a retrospective study of 44 adults with muscular FAODs from six French reference centers for neuromuscular or metabolic diseases.
    RESULTS: The study cohort consisted of 44 adult patients: 14 with carnitine palmitoyl transferase 2 deficiency (32%), nine with multiple acyl-CoA deficiency (20%), 13 with very long-chain acyl-CoA dehydrogenase deficiency (30%), three with long-chain 3-hydroxyacyl-CoA dehydrogenase deficiency (7%), and five with short-chain acyl-CoA dehydrogenase deficiency (11%). Disease onset occurred during childhood in the majority of patients (59%), with a mean age at onset of 15 years (range = 0.5-35) and a mean of 12.6 years (range = 0-58) from disease onset to diagnosis. The principal symptoms were acute muscle manifestations (rhabdomyolysis, exercise intolerance, myalgia), sometimes associated with permanent muscle weakness. Episodes of rhabdomyolysis were frequent (84%), with a mean creatinine kinase level of 68,958 U/L (range = 660-300,000). General metabolic complications were observed in 58% of patients, respiratory manifestations in 18% of cases, and cardiological manifestations in 9% of cases. Fasting acylcarnitine profile was used to orient genetic explorations in 65% of cases. After a mean follow-up of 10 years, 33% of patients were asymptomatic and 56% continued to display symptoms after exercise. The frequency of rhabdomyolysis decreased after diagnosis in 64% of cases.
    CONCLUSION: A standardized register would complete this cohort description of muscular forms of FAODs with exhaustive data, making it possible to assess the efficacy of therapeutic protocols in real-life conditions and during the long-term follow-up of patients.
    Keywords:  acylcarnitine profile; beta-oxidation; exercise intolerance; fatty acids; genetic analyses; long-term improvement; muscle weakness; rhabdomyolysis
    DOI:  https://doi.org/10.1111/ene.16138
  37. J Biochem. 2023 Nov 28. pii: mvad100. [Epub ahead of print]
    Supercomplex formation of mitochondrial respiratory chain complexes in leukocytes from patients with neurodegenerative diseases.
    Tsukasa Hara, Ryosuke Amagai, Ryuji Sakakibara, Ayako Okado-Matsumoto.
      With population aging, cognitive impairments and movement disorders due to neurodegenerative diseases, such as Alzheimer's disease (AD), Parkinson's disease (PD), and dementia with Lewy bodies (DLB), are increasingly considered as key social issues. Clinically, it has remained challenging to diagnose them before the onset of symptoms because of difficulty to observe the progressive loss of neurons in the brain. Therefore, with exploratory research into biomarkers, a number of candidates have previously been proposed, such as activities of mitochondrial respiratory chain complexes in blood in AD and PD. In this study, we focused on the formation of mitochondrial respiratory chain supercomplexes (SCs) because the formation of SC itself modulates the activity of each complex. Here we investigated the SC formation in leukocytes from patients with AD, PD, and DLB. Our results showed that SCs were well formed in AD and PD compared with controls, while poorly formed in DLB. We highlighted that the disruption of the SC formation correlated with the progression of PD and DLB. Taking our findings together, we propose that pronounced SC formation would already have occurred before the onset of AD, PD, and DLB and, with the progression of neurodegeneration, the SC formation would gradually be disrupted.
    Keywords:  Alzheimer’s disease; Parkinson’s disease; dementia with Lewy bodies; high-resolution clear native polyacrylamide gel electrophoresis; in-gel activity assay; mitochondrial respiratory chain complexes
    DOI:  https://doi.org/10.1093/jb/mvad100
  38. Biophys Rep. 2023 Jun 30. 9(3): 113-119
    Multi-phase separation in mitochondrial nucleoids and eukaryotic nuclei.
    Qi Long, Yanshuang Zhou, Jingyi Guo, Hao Wu, Xingguo Liu.
      In mammalian cells, besides nuclei, mitochondria are the only semi-autonomous organelles possessing own DNA organized in the form of nucleoids. While eukaryotic nuclear DNA compaction, chromatin compartmentalization and transcription are regulated by phase separation, our recent work proposed a model of mitochondrial nucleoid self-assembly and transcriptional regulation by multi-phase separation. Herein, we summarized the phase separation both in the nucleus and mitochondrial nucleoids, and did a comparison of the organization and activity regulating, which would provide new insight into the understanding of both architecture and genetics of nucleus and mitochondrial nucleoids.
    DOI:  https://doi.org/10.52601/bpr.2023.220018
  39. Mol Genet Genomic Med. 2023 Nov 28. e2328
    The clinical, myopathological, and genetic analysis of 155 Chinese mitochondrial ophthalmoplegia patients with mitochondrial DNA single large deletions.
    Yang Zhao, Yue Hou, Xutong Zhao, Tongling Liufu, Meng Yu, Wei Zhang, Zhiying Xie, Victor Wei Zhang, Yun Yuan, Zhaoxia Wang.
       BACKGROUND: Progressive external ophthalmoplegia (PEO) is a common subtype of mitochondrial encephalomyopathy.
    OBJECTIVE: The study aimed to investigate the relationship between mitochondrial DNA (mtDNA) abnormalities, muscle pathology, and clinical manifestations in Chinese patients with single large-scale mtDNA deletion presenting with PEO.
    METHODS: This is a retrospective single-center study. Patients with PEO who had a single large deletion in mitochondrial DNA were included in this study. The associations were analyzed between mtDNA deletion patterns, myopathological changes, and clinical characteristics.
    RESULTS: In total, 155 patients with mitochondrial PEO carrying single large-scale mtDNA mutations were enrolled, including 137 chronic progressive external ophthalmoplegia (CPEO) and 18 Kearns-Sayre syndrome (KSS) patients. The onset ages were 9.61 ± 4.12 in KSS and 20.15 ± 9.06 in CPEO. The mtDNA deletions ranged from 2225 bp to 9131 bp, with m.8470_13446del being the most common. The KSS group showed longer deletions than the CPEO group (p = 0.004). Additionally, a higher number of deleted genes encoding respiratory chain complex subunits (p = 0.001) and tRNA genes (p = 0.009) were also observed in the KSS group. A weak negative correlation between the mtDNA deletion size and ages of onset (p < 0.001, r = -0.369) was observed. The proportion of ragged red fibers, ragged blue fibers, and cytochrome c negative fibers did not correlate significantly with onset ages (p > 0.05). However, a higher percentage of abnormal muscle fibers corresponds to an increased prevalence of exercise intolerance, limb muscle weakness, dysphagia, and cerebellar ataxia.
    CONCLUSION: We reported a large Chinese cohort consisting of mitochondrial PEO patients with single large-scale mtDNA deletions. Our results demonstrated that the length and locations of mtDNA deletions may influence onset ages and clinical phenotypes. The severity of muscle pathology could not only indicate diagnosis but also may be associated with clinical manifestations beyond the extraocular muscles.
    Keywords:  Kearns-Sayre syndrome; chronic progressive external ophthalmoplegia; mitochondrial DNA; single large-scale deletion
    DOI:  https://doi.org/10.1002/mgg3.2328
  40. Commun Biol. 2023 Nov 25. 6(1): 1201
    ACO2 deficiency increases vulnerability to Parkinson's disease via dysregulating mitochondrial function and histone acetylation-mediated transcription of autophagy genes.
    Junge Zhu, Fanxi Xu, Hong Lai, Huiyao Yuan, Xu-Ying Li, Junya Hu, Wei Li, Lei Liu, Chaodong Wang.
      Parkinson's disease (PD) is characterized by α-synuclein aggregation in dopaminergic (DA) neurons, which are sensitive to oxidative stress. Mitochondria aconitase 2 (ACO2) is an essential enzyme in the tricarboxylic acid cycle that orchestrates mitochondrial and autophagic functions to energy metabolism. Though widely linked to diseases, its relation to PD has not been fully clarified. Here we revealed that the peripheral ACO2 activity was significantly decreased in PD patients and associated with their onset age and disease durations. The knock-in mouse and Drosophila models with the A252T variant displayed aggravated motor deficits and DA neuron degeneration after 6-OHDA and rotenone-induction, and the ACO2 knockdown or blockade cells showed features of mitochondrial and autophagic dysfunction. Moreover, the transcription of autophagy-related genes LC3 and Atg5 was significantly downregulated via inhibited histone acetylation at the H3K9 and H4K5 sites. These data provided multi-dimensional evidences supporting the essential roles of ACO2, and as a potential early biomarker to be used in clinical trials for assessing the effects of antioxidants in PD. Moreover, ameliorating energy metabolism by targeting ACO2 could be considered as a potential therapeutic strategy for PD and other neurodegenerative disorders.
    DOI:  https://doi.org/10.1038/s42003-023-05570-y
  41. Methods Mol Biol. 2024 ;2728 137-147
    Real-Time Assessment of Mitochondrial Function in Cytotrophoblast and Syncytialized Trophoblast Cells Using the Seahorse XFe24 Extracellular Flux Analyzer.
    O'Llenecia S Walker, Linda L May, Sandeep Raha.
      Physiological processes utilize variable amounts of energy required for optimal growth, development, and survival. This energy is supplied by total intracellular adenosine triphosphate (ATP) and is mainly generated by mitochondrial oxidative phosphorylation and to a lesser extent via glycolysis. Here, we provide a detailed protocol for obtaining measurements of energy metabolism using the Seahorse XFe24 Extracellular Flux Analyzer. Specifically, this assay measures mitochondrial oxidative phosphorylation based on oxygen consumption rate (OCR) and glycolysis by analyzing the extracellular acidification rate (ECAR) via real-time live cell analysis. Using trophoblast cell lines, this protocol focuses on analyzing mitochondrial respiration for both cytotrophoblasts and syncytiotrophoblasts.
    Keywords:  Mitochondria; OCR; Oxidative phosphorylation; Seahorse XF24 Extracellular Flux Analyzer; Trophoblasts
    DOI:  https://doi.org/10.1007/978-1-0716-3495-0_12
  42. Cureus. 2023 Oct;15(10): e47076
    Anesthetic Management for a Child With a Newly Identified Mitochondrial Disease SLC25A46 Mutation: A Case Report.
    Thong Nguyen, Sarah Shabot, David Yngve, Amr Abouleish.
      SLC25A46 mutation is a newly recognized mitochondrial mutation causing neurological and muscular abnormalities. We describe a first-ever report of the anesthetic management of a seven-year-old boy with an SLC25A46 mutation during a major orthopedic procedure. The patient was nonverbal and presented with cerebral visual impairment, torticollis, and lower extremity contractures. Because of his new diagnosis of mitochondrial disease and history of delayed awakening after anesthesia, we performed general anesthesia with sevoflurane, a low-dose ketamine infusion, and small doses of fentanyl while avoiding propofol and maintaining normoglycemia and normothermia. No postoperative complications were noted during the recovery period.
    Keywords:  anesthetic management; cerebral palsy; femoral osteotomy; intra-iliac osteotomy; mitochondrial disease; slc25a46 mutation
    DOI:  https://doi.org/10.7759/cureus.47076
  43. Commun Med (Lond). 2023 Nov 25. 3(1): 169
    O-GlcNAcylation is essential for therapeutic mitochondrial transplantation.
    Ji Hyun Park, Masayoshi Tanaka, Takafumi Nakano, Ester Licastro, Yoshihiko Nakamura, Wenlu Li, Elga Esposito, Emiri T Mandeville, Sherry Hsiang-Yi Chou, MingMing Ning, Eng H Lo, Kazuhide Hayakawa.
       BACKGROUND: Transplantation of mitochondria is increasingly explored as a novel therapy in central nervous system (CNS) injury and disease. However, there are limitations in safety and efficacy because mitochondria are vulnerable in extracellular environments and damaged mitochondria can induce unfavorable danger signals.
    METHODS: Mitochondrial O-GlcNAc-modification was amplified by recombinant O-GlcNAc transferase (OGT) and UDP-GlcNAc. O-GlcNAcylated mitochondrial proteins were identified by mass spectrometry and the antiglycation ability of O-GlcNAcylated DJ1 was determined by loss-of-function via mutagenesis. Therapeutic efficacy of O-GlcNAcylated mitochondria was assessed in a mouse model of transient focal cerebral ischemia-reperfusion. To explore translational potential, we evaluated O-GlcNAcylated DJ1 in CSF collected from patients with subarachnoid hemorrhagic stroke (SAH).
    RESULTS: We show that isolated mitochondria are susceptible to advanced glycation end product (AGE) modification, and these glycated mitochondria induce the receptor for advanced glycation end product (RAGE)-mediated autophagy and oxidative stress when transferred into neurons. However, modifying mitochondria with O-GlcNAcylation counteracts glycation, diminishes RAGE-mediated effects, and improves viability of mitochondria recipient neurons. In a mouse model of stroke, treatment with extracellular mitochondria modified by O-GlcNAcylation reduces neuronal injury and improves neurologic deficits. In cerebrospinal fluid (CSF) samples from SAH patients, levels of O-GlcNAcylation in extracellular mitochondria correlate with better clinical outcomes.
    CONCLUSIONS: These findings suggest that AGE-modification in extracellular mitochondria may induce danger signals, but O-GlcNAcylation can prevent glycation and improve the therapeutic efficacy of transplanted mitochondria in the CNS.
    DOI:  https://doi.org/10.1038/s43856-023-00402-w
  44. JBMR Plus. 2023 Nov;7(11): e10824
    Skeletal Health in Patients With Mitochondrial Diabetes: Case Series and Review of Literature.
    Kagan Ege Karakus, Varun Suryadevara, Austin Larson, Prathosh Gangadhar, Viral N Shah.
      Monogenic diabetes, including mitochondrial diabetes, constitutes 1% to 3% of all diabetes. Although there is an increased interest in understanding the mechanisms of bone fragility in people with diabetes, skeletal research is mostly focused on type 1 and type 2 diabetes. Little is known on skeletal health among people with mitochondrial diabetes. In this single-center study, we presented clinical characteristics of individuals with mitochondrial diabetes and clinical diagnosis of osteoporosis. Of 10 patients with mitochondrial diabetes, 4 (40%) had a clinical diagnosis of osteoporosis. Patients with osteoporosis were older, had lower body mass index, longer diabetes duration, lower fasting C-peptide, and presence of multiple comorbidities compared with patients without osteoporosis. In addition to our cases, we also systematically reviewed literature on skeletal health in people with mitochondrial diabetes and provided an overview of potential factors affecting skeletal health and future clinical and research directions to improve the care of people with mitochondrial disease. © 2023 The Authors. JBMR Plus published by Wiley Periodicals LLC on behalf of American Society for Bone and Mineral Research.
    Keywords:  DIABETES; DXA; FRACTURE; MITOCHONDRIAL DIABETES; OSTEOPOROSIS; PRIMARY MITOCHONDRIAL DISEASE; SKELETAL HEALTH
    DOI:  https://doi.org/10.1002/jbm4.10824
  45. Epigenomics. 2023 Nov;15(21): 1121-1136
    Decoding mitochondrial-nuclear (epi)genome interactions: the emerging role of ncRNAs.
    Julia Nguyen, Quinn Le, Phyo W Win, Kathleen A Hill, Shiva M Singh, Christina A Castellani.
      Bidirectional communication between the mitochondria and the nucleus is required for several physiological processes, and the nuclear epigenome is a key mediator of this relationship. ncRNAs are an emerging area of discussion for their roles in cellular function and regulation. In this review, we highlight the role of mitochondrial-encoded ncRNAs as mediators of communication between the mitochondria and the nuclear genome. We focus primarily on retrograde signaling, a process in which the mitochondrion relays ncRNAs to translate environmental stress signals to changes in nuclear gene expression, with implications on stress responses that may include disease(s). Other biological roles of mitochondrial-encoded ncRNAs, such as mitochondrial import of proteins and regulation of cell signaling, will also be discussed.
    Keywords:  disease risk; gene expression; mitochondria; ncRNA; retrograde signaling
    DOI:  https://doi.org/10.2217/epi-2023-0322
  46. Zhonghua Er Ke Za Zhi. 2023 Dec 02. 61(12): 1077-1085
    [Expert consensus on the diagnosis and treatment of Leigh syndrome (2023)].
    Subspecialty Group of Neurology, the Society of Pediatrics, Chinese Medical Association
      
    DOI:  https://doi.org/10.3760/cma.j.cn112140-20230904-00153
  47. Autophagy. 2023 Dec 02. 1-12
    Basal activity of PINK1 and PRKN in cell models and rodent brain.
    Jens O Watzlawik, Fabienne C Fiesel, Gabriella Fiorino, Bernardo A Bustillos, Zahra Baninameh, Briana N Markham, Xu Hou, Caleb S Hayes, Jenny M Bredenberg, Nicholas W Kurchaba, Dominika Fričová, Joanna Siuda, Zbigniew K Wszolek, Sachiko Noda, Shigeto Sato, Nobutaka Hattori, Asheeta A Prasad, Deniz Kirik, Howard S Fox, Kelly L Stauch, Matthew S Goldberg, Wolfdieter Springer.
      The ubiquitin kinase-ligase pair PINK1-PRKN recognizes and transiently labels damaged mitochondria with ubiquitin phosphorylated at Ser65 (p-S65-Ub) to mediate their selective degradation (mitophagy). Complete loss of PINK1 or PRKN function unequivocally leads to early-onset Parkinson disease, but it is debated whether impairments in mitophagy contribute to disease later in life. While the pathway has been extensively studied in cell culture upon acute and massive mitochondrial stress, basal levels of activation under endogenous conditions and especially in vivo in the brain remain undetermined. Using rodent samples, patient-derived cells, and isogenic neurons, we here identified age-dependent, brain region-, and cell type-specific effects and determined expression levels and extent of basal and maximal activation of PINK1 and PRKN. Our work highlights the importance of defining critical risk and therapeutically relevant levels of PINK1-PRKN signaling which will further improve diagnosis and prognosis and will lead to better stratification of patients for future clinical trials.
    Keywords:  Mitophagy; PINK1; PRKN; Parkinson disease; parkin; ubiquitin
    DOI:  https://doi.org/10.1080/15548627.2023.2286414
  48. Nat Commun. 2023 Nov 28. 14(1): 7793
    NR-SAFE: a randomized, double-blind safety trial of high dose nicotinamide riboside in Parkinson's disease.
    Haakon Berven, Simon Kverneng, Erika Sheard, Mona Søgnen, Solveig Amdahl Af Geijerstam, Kristoffer Haugarvoll, Geir-Olve Skeie, Christian Dölle, Charalampos Tzoulis.
      Nicotinamide adenine dinucleotide (NAD) replenishment therapy using nicotinamide riboside (NR) shows promise for Parkinson's disease (PD) and other neurodegenerative disorders. However, the optimal dose of NR remains unknown, and doses exceeding 2000 mg daily have not been tested in humans. To evaluate the safety of high-dose NR therapy, we conducted a single-center, randomized, placebo-controlled, double-blind, phase I trial on 20 individuals with PD, randomized 1:1 on NR 1500 mg twice daily (n = 10) or placebo (n = 10) for four weeks. The trial was conducted at the Department of Neurology, Haukeland University Hospital, Bergen, Norway. The primary outcome was safety, defined as the frequency of moderate and severe adverse events. Secondary outcomes were tolerability defined as frequency of mild adverse events, change in the whole blood and urine NAD metabolome, and change in the clinical severity of PD, measured by MDS-UPDRS. All 20 participants completed the trial. The trial met all prespecified outcomes. NR therapy was well tolerated with no moderate or severe adverse events, and no significant difference in mild adverse events. NR therapy was associated with clinical improvement of total MDS-UPDRS scores. However, this change was also associated with a shorter interval since the last levodopa dose. NR greatly augmented the blood NAD metabolome with up to 5-fold increase in blood NAD+ levels. While NR-recipients exhibited a slight initial rise in serum homocysteine levels, the integrity of the methyl donor pool remained intact. Our results support extending the dose range of NR in phase II clinical trials to 3000 mg per day, with appropriate safety monitoring. Clinicaltrials.gov identifier: NCT05344404.
    DOI:  https://doi.org/10.1038/s41467-023-43514-6
  49. Pediatr Transplant. 2023 Nov 27. e14659
    Living donor liver transplantation for myocerebrohepatopathy spectrum due to POLG mutations.
    Masashi Kadohisa, Tatsuya Okamoto, Miki Yamamoto, Elena Yukie Uebayashi, Mari Sonoda, Eri Ogawa, Atsushi Yokoyama, Hidenori Kawasaki, Eitaro Hiejima, Shogo Ito, Takao Togawa, Kazuo Imagawa, Kei Murayama, Hideaki Okajima, Etsuro Hatano.
       BACKGROUND: POLG is one of several nuclear genes associated with mitochondrial DNA maintenance defects and is a group of diseases caused by mitochondrial DNA deficiency that results in impaired adenosine triphosphate production and organ dysfunction. Myocerebrohepatopathy spectrum (MCHS) is the most severe and earliest presentation of POLG mutations, and liver transplantation (LT) for MCHS has never been reported.
    CASE PRESENTATION: The patient was a 3-month-old boy with acute liver failure and no neurological manifestations (e.g., seizures). We performed a living donor LT using a left lateral segment graft from his father. The postoperative course was uneventful. Subsequently, a homozygous POLG mutation (c.2890C>T, p. R964C) was identified by multigene analysis of neonatal/infantile intrahepatic cholestasis. Moreover, respiratory chain complex I, II, and III enzyme activities and the ratio of mtDNA to nuclear DNA in the liver were reduced. Therefore, we considered that these clinical manifestations and examination findings met the definition for MCHS. During meticulous follow-up, the patient had shown satisfactory physical growth and mental development until the time of writing this report.
    CONCLUSION: We presumed that the absence of remarkable neurologic manifestations prior to LT in patients with MCHS is a good indication for LT and contributes to a better prognosis in the present case.
    Keywords:  POLG; liver transplantation; mitochondrial DNA maintenance defect; myocerebrohepatopathy spectrum; respiratory chain complexes
    DOI:  https://doi.org/10.1111/petr.14659
  50. Cell Death Dis. 2023 Nov 25. 14(11): 772
    Negative modulation of mitochondrial calcium uniporter complex protects neurons against ferroptosis.
    Alejandro Marmolejo-Garza, Inge E Krabbendam, Minh Danh Anh Luu, Famke Brouwer, Marina Trombetta-Lima, Osman Unal, Shane J O'Connor, Naďa Majerníková, Carolina R S Elzinga, Cristina Mammucari, Martina Schmidt, Muniswamy Madesh, Erik Boddeke, Amalia M Dolga.
      Ferroptosis is an iron- and reactive oxygen species (ROS)-dependent form of regulated cell death, that has been implicated in Alzheimer's disease and Parkinson's disease. Inhibition of cystine/glutamate antiporter could lead to mitochondrial fragmentation, mitochondrial calcium ([Ca2+]m) overload, increased mitochondrial ROS production, disruption of the mitochondrial membrane potential (ΔΨm), and ferroptotic cell death. The observation that mitochondrial dysfunction is a characteristic of ferroptosis makes preservation of mitochondrial function a potential therapeutic option for diseases associated with ferroptotic cell death. Mitochondrial calcium levels are controlled via the mitochondrial calcium uniporter (MCU), the main entry point of Ca2+ into the mitochondrial matrix. Therefore, we have hypothesized that negative modulation of MCU complex may confer protection against ferroptosis. Here we evaluated whether the known negative modulators of MCU complex, ruthenium red (RR), its derivative Ru265, mitoxantrone (MX), and MCU-i4 can prevent mitochondrial dysfunction and ferroptotic cell death. These compounds mediated protection in HT22 cells, in human dopaminergic neurons and mouse primary cortical neurons against ferroptotic cell death. Depletion of MICU1, a [Ca2+]m gatekeeper, demonstrated that MICU is protective against ferroptosis. Taken together, our results reveal that negative modulation of MCU complex represents a therapeutic option to prevent degenerative conditions, in which ferroptosis is central to the progression of these pathologies.
    DOI:  https://doi.org/10.1038/s41419-023-06290-1
  51. Am J Hum Genet. 2023 Nov 20. pii: S0002-9297(23)00367-1. [Epub ahead of print]
    Improved detection of aberrant splicing with FRASER 2.0 and the intron Jaccard index.
    Ines F Scheller, Karoline Lutz, Christian Mertes, Vicente A Yépez, Julien Gagneur.
      Detection of aberrantly spliced genes is an important step in RNA-seq-based rare-disease diagnostics. We recently developed FRASER, a denoising autoencoder-based method that outperformed alternative methods of detecting aberrant splicing. However, because FRASER's three splice metrics are partially redundant and tend to be sensitive to sequencing depth, we introduce here a more robust intron-excision metric, the intron Jaccard index, that combines the alternative donor, alternative acceptor, and intron-retention signal into a single value. Moreover, we optimized model parameters and filter cutoffs by using candidate rare-splice-disrupting variants as independent evidence. On 16,213 GTEx samples, our improved algorithm, FRASER 2.0, called typically 10 times fewer splicing outliers while increasing the proportion of candidate rare-splice-disrupting variants by 10-fold and substantially decreasing the effect of sequencing depth on the number of reported outliers. To lower the multiple-testing correction burden, we introduce an option to select the genes to be tested for each sample instead of a transcriptome-wide approach. This option can be particularly useful when prior information, such as candidate variants or genes, is available. Application on 303 rare-disease samples confirmed the relative reduction in the number of outlier calls for a slight loss of sensitivity; FRASER 2.0 recovered 22 out of 26 previously identified pathogenic splicing cases with default cutoffs and 24 when multiple-testing correction was limited to OMIM genes containing rare variants. Altogether, these methodological improvements contribute to more effective RNA-seq-based rare diagnostics by drastically reducing the amount of splicing outlier calls per sample at minimal loss of sensitivity.
    Keywords:  Aberrant splicing; RNA-seq; outlier detection; rare disease; rare disease diagnostics; rare variant
    DOI:  https://doi.org/10.1016/j.ajhg.2023.10.014
  52. Cond Med. 2022 Dec;5(6): 192-195
    Commentary: Can astrocytic mitochondria therapy be used as antioxidant conditioning to protect neurons?
    Kazuhide Hayakawa.
      In the context of central nervous system (CNS) disease, oxidative stress may cause progression of cell death and neuroinflammation. Therefore, restoring mitochondrial antioxidant ability within cells is a major therapeutic strategy in many CNS disorders. A recent study uncovers a novel mechanism of astrocytic mitochondria being neuroprotective after intracerebral hemorrhage in mice. In their work, systemic administration of mitochondria obtained from astrocytes restores neuronal antioxidant defense, prevents neuronal death while promoting neurite outgrowth, indicating that extracellular mitochondria may play key roles in mediating beneficial non-cell autonomous effects. Given that mitochondria are also responsible for tolerance to stress and injury, is it possible that exogenous mitochondria signals may regulate cellular conditioning by boosting antioxidant ability? Further studies are warranted to build on these emerging findings in the pursuit of conditioning therapies mediated by mitochondrial transplantation in CNS injury and disease.
    Keywords:  Antioxidant defense; Astrocytic mitochondria; CNS disorders; Mitochondrial transplantation
  53. Am J Physiol Heart Circ Physiol. 2023 Dec 01.
    A modified mouse model of Friedreich's ataxia with conditional Fxn allele homozygosity delays onset of cardiomyopathy.
    Tyler L Perfitt, Claudia Huichalaf, Renea Gooch, Anna Kuperman, Youngwook Ahn, Xian Chen, Soumya Ullas, Dinesh Hirenallur-Shanthappa, Yutian Zhan, Diana Otis, Laurence O Whiteley, Christine Bulawa, Alain Martelli.
      Friedreich's ataxia (FA) is an autosomal recessive disorder caused by a deficiency in frataxin (FXN), a mitochondrial protein that plays a critical role in the synthesis of iron sulfur clusters (Fe-S), vital inorganic cofactors necessary for numerous cellular processes. FA is characterized by progressive ataxia and hypertrophic cardiomyopathy, with cardiac dysfunction as the most common cause of mortality in patients. Commonly used cardiac-specific mouse models of FA utilize the muscle creatine kinase (MCK) promoter to express Cre recombinase in cardiomyocytes and striated muscle cells in mice with one conditional Fxn allele and one floxed-out/null allele. These mice quickly develop cardiomyopathy that becomes fatal by 9-11 weeks of age. Here, we generated a cardiac-specific model with floxed Fxn allele homozygosity (MCK-Fxnflox/flox). MCK-Fxnflox/flox mice were phenotypically normal at 9 weeks of age, despite no detectable FXN protein expression. Between 13 and 15 weeks of age, these mice began to display progressive cardiomyopathy, including decreased ejection fraction and fractional shortening, and increased left ventricular mass. MCK-Fxnflox/flox mice began to lose weight around 16 weeks of age, characteristically associated with heart failure in other cardiac-specific FA models. By 18 weeks of age, MCK-Fxnflox/flox mice displayed elevated markers of Fe-S deficiency, cardiac stress and injury, and cardiac fibrosis. This modified model reproduced important pathophysiological and biochemical features of FA over a longer timescale than previous cardiac-specific mouse models, offering a larger window for studying potential therapeutics.
    Keywords:  Friedreich's ataxia; animal models; cardiac diseases; genetic diseases
    DOI:  https://doi.org/10.1152/ajpheart.00496.2023
  54. bioRxiv. 2023 Nov 13. pii: 2023.11.13.566839. [Epub ahead of print]
    COQ4 is required for the oxidative decarboxylation of the C1 carbon of Coenzyme Q in eukaryotic cells.
    Ludovic Pelosi, Laura Morbiato, Arthur Burgardt, Fiorella Tonello, Abigail K Bartlett, Rachel M Guerra, Katayoun Kazemzadeh Ferizhendi, Maria Andrea Desbats, Bérengère Rascalou, Marco Marchi, Luis Vázquez-Fonseca, Caterina Agosto, Giuseppe Zanotti, Morgane Roger-Margueritat, María Alcázar-Fabra, Laura García-Corzo, Ana Sánchez-Cuesta, Plácido Navas, Gloria Brea-Calvo, Eva Trevisson, Volker F Wendisch, David J Pagliarini, Leonardo Salviati, Fabien Pierrel.
      Coenzyme Q (CoQ) is a redox lipid that fulfills critical functions in cellular bioenergetics and homeostasis. CoQ is synthesized by a multi-step pathway that involves several COQ proteins. Two steps of the eukaryotic pathway, the decarboxylation and hydroxylation of position C1, have remained uncharacterized. Here, we provide evidence that these two reactions occur in a single oxidative decarboxylation step catalyzed by COQ4. We demonstrate that COQ4 complements an Escherichia coli strain deficient for C1 decarboxylation and hydroxylation and that COQ4 displays oxidative decarboxylation activity in the non-CoQ producer Corynebacterium glutamicum . Overall, our results substantiate that COQ4 contributes to CoQ biosynthesis, not only via its previously proposed structural role, but also via oxidative decarboxylation of CoQ precursors. These findings fill a major gap in the knowledge of eukaryotic CoQ biosynthesis, and shed new light on the pathophysiology of human primary CoQ deficiency due to COQ4 mutations.
    DOI:  https://doi.org/10.1101/2023.11.13.566839
  55. Nat Commun. 2023 Nov 28. 14(1): 7805
    PhenoSV: interpretable phenotype-aware model for the prioritization of genes affected by structural variants.
    Zhuoran Xu, Quan Li, Luigi Marchionni, Kai Wang.
      Structural variants (SVs) represent a major source of genetic variation associated with phenotypic diversity and disease susceptibility. While long-read sequencing can discover over 20,000 SVs per human genome, interpreting their functional consequences remains challenging. Existing methods for identifying disease-related SVs focus on deletion/duplication only and cannot prioritize individual genes affected by SVs, especially for noncoding SVs. Here, we introduce PhenoSV, a phenotype-aware machine-learning model that interprets all major types of SVs and genes affected. PhenoSV segments and annotates SVs with diverse genomic features and employs a transformer-based architecture to predict their impacts under a multiple-instance learning framework. With phenotype information, PhenoSV further utilizes gene-phenotype associations to prioritize phenotype-related SVs. Evaluation on extensive human SV datasets covering all SV types demonstrates PhenoSV's superior performance over competing methods. Applications in diseases suggest that PhenoSV can determine disease-related genes from SVs. A web server and a command-line tool for PhenoSV are available at https://phenosv.wglab.org .
    DOI:  https://doi.org/10.1038/s41467-023-43651-y
  56. Front Endocrinol (Lausanne). 2023 ;14 1268135
    Case report: Two unexpected cases of DGUOK-related mitochondrial DNA depletion syndrome presenting with hyperinsulinemic hypoglycemia.
    Herodes Guzman, Sahr Yazdani, Jennifer L Harmon, Kimberly A Chapman, Bernadette Vitola, Louise Pyle, Heather McKnight, Winnie Sigal, Katherine Lord, Diva D De Leon, Nadia Merchant, Rebecca Ganetzky.
      Timely diagnosis of persistent neonatal hypoglycemia is critical to prevent neurological sequelae, but diagnosis is complicated by the heterogenicity of the causes. We discuss two cases at separate institutions in which clinical management was fundamentally altered by the results of molecular genetic testing. In both patients, critical samples demonstrated hypoketotic hypoglycemia and a partial glycemic response to glucagon stimulation, thereby suggesting hyperinsulinism (HI). However, due to rapid genetic testing, both patients were found to have deoxyguanosine kinase (DGUOK)-related mitochondrial DNA depletion syndrome, an unexpected diagnosis. Patients with this disease typically present with either hepatocerebral disease in the neonatal period or isolated hepatic failure in infancy. The characteristic features involved in the hepatocerebral form of the disease include lactic acidosis, hypoglycemia, cholestasis, progressive liver failure, and increasing neurologic dysfunction. Those with isolated liver involvement experience hepatomegaly, cholestasis, and liver failure. Although liver transplantation is considered, research has demonstrated that for patients with DGUOK-related mitochondrial DNA depletion syndrome and neurologic symptoms, early demise occurs. Our report advocates for the prompt initiation of genetic testing in patients presenting with persistent neonatal hypoglycemia and for the incorporation of mitochondrial DNA depletion syndromes in the differential diagnosis of HI.
    Keywords:  DGUOK; exome; hyperinsulinism; hypoglycemia; mitochondria
    DOI:  https://doi.org/10.3389/fendo.2023.1268135
  57. CNS Neurosci Ther. 2023 Nov 27.
    Biallelic variants in the COQ4 gene caused hereditary spastic paraplegia predominant phenotype.
    Qiao Wei, Hao Yu, Pei-Shan Wang, Juan-Juan Xie, Hai-Lin Dong, Zhi-Ying Wu, Hong-Fu Li.
       INTRODUCTION: Hereditary spastic paraplegias (HSPs) comprise a group of neurodegenerative disorders characterized by progressive degeneration of upper motor neurons. Homozygous or compound heterozygous variants in COQ4 have been reported to cause primary CoQ10 deficiency-7 (COQ10D7), which is a mitochondrial disease.
    AIMS: We aimed to screened COQ4 variants in a cohort of HSP patients.
    METHODS: A total of 87 genetically unidentified HSP index patients and their available family members were recruited. Whole exome sequencing (WES) was performed in all probands. Functional studies were performed to identify the pathogenicity of those uncertain significance variants.
    RESULTS: In this study, five different COQ4 variants were identified in three Chinese HSP pedigrees and two variants were novel, c.87dupT (p.Arg30*), c.304C>T (p.Arg102Cys). More importantly, we firstly described two early-onset pure HSP caused by COQ4 variants. Functional studies in patient-derived fibroblast lines revealed a reduction cellular CoQ10 levels and the abnormal mitochondrial structure.
    CONCLUSIONS: Our findings revealed that bilateral variants in the COQ4 gene caused HSP predominant phenotype, expanding the phenotypic spectrum of the COQ4-related disorders.
    Keywords:   COQ4 ; Chinese; hereditary spastic paraplegia; novel phenotype
    DOI:  https://doi.org/10.1111/cns.14529
  58. Front Genet. 2023 ;14 1277948
    The implementation and utility of clinical exome sequencing in a South African infant cohort.
    L Campbell, J Fredericks, K Mathivha, P Moshesh, A Coovadia, P Chirwa, B Dillon, A Ghoor, D Lawrence, L Nair, N Mabaso, D Mokwele, M Novellie, A Krause, N Carstens.
      Genetic disorders are significant contributors to infant hospitalization and mortality globally. The early diagnosis of these conditions in infants remains a considerable challenge. Clinical exome sequencing (CES) has shown to be a successful tool for the early diagnosis of genetic conditions, however, its utility in African infant populations has not been investigated. The impact of the under-representation of African genomic data, the cost of testing, and genomic workforce shortages, need to be investigated and evidence-based implementation strategies accounting for locally available genetics expertise and diagnostic infrastructure need to be developed. We evaluated the diagnostic utility of singleton CES in a cohort of 32 ill, South African infants from two State hospitals in Johannesburg, South Africa. We analysed the data using a series of filtering approaches, including a curated virtual gene panel consisting of genes implicated in neonatal-and early childhood-onset conditions and genes with known founder and common variants in African populations. We reported a diagnostic yield of 22% and identified seven pathogenic variants in the NPHS1, COL2A1, OCRL, SHOC2, TPRV4, MTM1 and STAC3 genes. This study demonstrates the utility value of CES in the South African State healthcare setting, providing a diagnosis to patients who would otherwise not receive one and allowing for directed management. We anticipate an increase in the diagnostic yield of our workflow with further refinement of the study inclusion criteria. This study highlights important considerations for the implementation of genomic medicine in under-resourced settings and in under-represented African populations where variant interpretation remains a challenge.
    Keywords:  LMIC; South Africa; clinical-exome; diagnostic; implementation; infant
    DOI:  https://doi.org/10.3389/fgene.2023.1277948
  59. Mol Med. 2023 Nov 28. 29(1): 161
    IGF2 deficiency promotes liver aging through mitochondrial dysfunction and upregulated CEBPB signaling in D-galactose-induced aging mice.
    Xiaohai Zhou, Bowen Tan, Weiwei Gui, Caiping Zhou, Hanxin Zhao, Xihua Lin, Hong Li.
       BACKGROUND: Liver aging, marked by cellular senescence and low-grade inflammation, heightens susceptibility to chronic liver disease and worsens its prognosis. Insulin-like growth factor 2 (IGF2) has been implicated in numerous aging-related diseases. Nevertheless, its role and underlying molecular mechanisms in liver aging remain largely unexplored.
    METHODS: The expression of IGF2 was examined in the liver of young (2-4 months), middle-aged (9-12 months), and old (24-26 months) C57BL/6 mice. In vivo, we used transgenic IGF2f/f; Alb-Cre mice and D-galactose-induced aging model to explore the role of IGF2 in liver aging. In vitro, we used specific short hairpin RNA against IGF2 to knock down IGF2 in AML12 cells. D-galactose and hydrogen peroxide treatment were used to induce AML12 cell senescence.
    RESULTS: We observed a significant reduction of IGF2 levels in the livers of aged mice. Subsequently, we demonstrated that IGF2 deficiency promoted senescence phenotypes and senescence-associated secretory phenotypes (SASPs), both in vitro and in vivo aging models. Moreover, IGF2 deficiency impaired mitochondrial function, reducing mitochondrial respiratory capacity, mitochondrial membrane potential, and nicotinamide adenine dinucleotide (NAD)+/NADH ratio, increasing intracellular and mitochondrial reactive oxygen species levels, and disrupting mitochondrial membrane structure. Additionally, IGF2 deficiency markedly upregulated CCAAT/enhancer-binding protein beta (CEBPB). Notably, inhibiting CEBPB reversed the senescence phenotypes and reduced SASPs induced by IGF2 deficiency.
    CONCLUSIONS: In summary, our findings strongly suggest that IGF2 deficiency promotes liver aging through mitochondrial dysfunction and upregulated CEBPB signaling. These results provide compelling evidence for considering IGF2 as a potential target for interventions aimed at slowing down the process of liver aging.
    Keywords:  Aging; CEBPB; IGF2; Liver; Mitochondria dysfunction
    DOI:  https://doi.org/10.1186/s10020-023-00752-0
  60. Exp Mol Med. 2023 Dec 01.
    Mitochondrial nucleic acids in innate immunity and beyond.
    Jimin Yoon, Sujin Kim, Mihye Lee, Yoosik Kim.
      Mitochondria participate in a wide range of cellular processes. One essential function of mitochondria is to be a platform for antiviral signaling proteins during the innate immune response to viral infection. Recently, studies have revealed that mitochondrion-derived DNAs and RNAs are recognized as non-self molecules and act as immunogenic ligands. More importantly, the cytosolic release of these mitochondrial nucleic acids (mt-NAs) is closely associated with the pathogenesis of human diseases accompanying aberrant immune activation. The release of mitochondrial DNAs (mtDNAs) via BAX/BAK activation and/or VDAC1 oligomerization activates the innate immune response and inflammasome assembly. In addition, mitochondrial double-stranded RNAs (mt-dsRNAs) are sensed by pattern recognition receptors in the cytosol to induce type I interferon expression and initiate apoptotic programs. Notably, these cytosolic mt-NAs also mediate adipocyte differentiation and contribute to mitogenesis and mitochondrial thermogenesis. In this review, we summarize recent studies of innate immune signaling pathways regulated by mt-NAs, human diseases associated with mt-NAs, and the emerging physiological roles of mt-NAs.
    DOI:  https://doi.org/10.1038/s12276-023-01121-x
  61. Nature. 2023 Nov 30.
    Tiny robots made from human cells heal damaged tissue.
    Matthew Hutson.
      
    Keywords:  Engineering; Personalized medicine
    DOI:  https://doi.org/10.1038/d41586-023-03777-x
  62. Epilepsia Open. 2023 Nov 27.
    Clinical and genetic analysis of infants with Pontocerebellar Hypoplasia Type 6 caused by RARS2 variations.
    Shichao Zhao, Ruofei Lian, Liang Jin, Mengchun Li, Tianming Jia, Falin Xu, Kaixian Du, Lijun Wang, Qiliang Guo, Yan Dong.
       OBJECTIVE: Defects in RARS2 cause cerebellopontine hypoplasia type 6 (Pontocerebellar Hypoplasia Type 6, PCH6, OMIM: #611523), a rare autosomal recessive inherited mitochondrial disease. Here, we report two male patients and their respective family histories.
    METHODS: We describe the clinical presentation and magnetic resonance imaging (MRI) findings of these patients. Whole-exome sequencing was used to identify the genetic mutations.
    RESULTS: One patient showed hypoglycemia, high lactic acid levels (fluctuating from 6.7 to 14.1 mmol/l), and frequent seizures after birth, with progressive atrophy of the cerebrum, cerebellum, and pons. The other patient presented with early infantile developmental and epileptic encephalopathies (EIDEEs) with an initial developmental delay followed by infantile epileptic spasm syndrome (IESS) at 5 months old, with no imaging changes. Whole-exome sequencing identified compound heterozygous RARS2 variants c.25A>G (p.I9V) with c.1261C>T (p.Q421 *) and c.1A>G (p.M1V) with c.122A>G (p.D41G) in these two patients. Of these loci, c.1261C>T and c.122A>G have not been previously reported.
    SIGNIFICANCE: Our findings have expanded the RARS2 gene variant spectrum, and present EIDEEs and IESS as phenotypes which deepened the association between PCH6 and RARS2.
    Keywords:  EIDEEs; IESS; Pontocerebellar Hypoplasia Type 6; RARS2
    DOI:  https://doi.org/10.1002/epi4.12862
  63. Nature. 2023 Nov;623(7989): 916
    Adjust the format of papers to improve description by AI.
    Terence Day.
      
    Keywords:  Communication; Machine learning; Publishing
    DOI:  https://doi.org/10.1038/d41586-023-03739-3
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