bims-mitmed Biomed News
on Mitochondrial medicine
Issue of 2022‒05‒22
23 papers selected by
Dario Brunetti
Fondazione IRCCS Istituto Neurologico
  1. Mitochondrial complex complexification.
  2. Cryo-EM structures define ubiquinone-10 binding to mitochondrial complex I and conformational transitions accompanying Q-site occupancy.
  3. TALEDs complete the toolkit for editing human mitochondrial DNA.
  4. Mitochondrial-derived vesicles: Recent insights.
  5. Altered Mitochondrial Protein Homeostasis and Proteinopathies.
  6. Targeting Mitochondrial bioenergetics as a promising therapeutic strategy in metabolic and neurodegenerative diseases.
  7. Are mitophagy enhancers therapeutic targets for Alzheimer's disease?
  8. SQSTM1 and its MAP1LC3B-binding domain induce forced mitophagy to degrade mitochondrial carryover during mitochondrial replacement therapy.
  9. Mitochondrial transfer/transplantation: an emerging therapeutic approach for multiple diseases.
  10. What Is the Role of Mitochondrial Dysfunction in Programmed Axon Death?
  11. Ambra1 deficiency impairs mitophagy in skeletal muscle.
  12. Metabolites: Fuelling the Immune Response.
  13. Neuron-astrocyte transmitophagy is altered in Alzheimer's disease.
  14. Genome Engineering Human ESCs or iPSCs with Cytosine and Adenine Base Editors.
  15. Simultaneous Quantification of Mitochondrial Mature Frataxin and Extra-Mitochondrial Frataxin Isoform E in Friedreich's Ataxia Blood.
  16. Autosomal recessive spinocerebellar ataxia SCAR8/ARCA1: first families detected in Spain.
  17. Labeling and Tracking Mitochondria with Photoactivation in Drosophila Embryos.
  18. Mitochondrial calcium uniporter stabilization preserves energetic homeostasis during Complex I impairment.
  19. Identification of a modulator of the actin cytoskeleton, mitochondria, nutrient metabolism and lifespan in yeast.
  20. Identification of adeno-associated virus variants for gene transfer into human neural cell types by parallel capsid screening.
  21. Association between sperm mitochondrial DNA copy number and deletion rate and industrial air pollution dynamics.
  22. Age-Dependent Alterations of Cognition, Mitochondrial Function, and Beta-Amyloid Deposition in a Murine Model of Alzheimer's Disease-A Longitudinal Study.
  23. Lipid droplet degradation by autophagy connects mitochondria metabolism to Prox1-driven expression of lymphatic genes and lymphangiogenesis.
  1. Science. 2022 May 20. 376(6595): 794-795
    Mitochondrial complex complexification.
    Martijn A Huynen, Dei M Elurbe.
      Variation in complex composition provides clues about the function of individual subunits.
    DOI:  https://doi.org/10.1126/science.abq0368
  2. Nat Commun. 2022 May 19. 13(1): 2758
    Cryo-EM structures define ubiquinone-10 binding to mitochondrial complex I and conformational transitions accompanying Q-site occupancy.
    Injae Chung, John J Wright, Hannah R Bridges, Bozhidar S Ivanov, Olivier Biner, Caroline S Pereira, Guilherme M Arantes, Judy Hirst.
      Mitochondrial complex I is a central metabolic enzyme that uses the reducing potential of NADH to reduce ubiquinone-10 (Q10) and drive four protons across the inner mitochondrial membrane, powering oxidative phosphorylation. Although many complex I structures are now available, the mechanisms of Q10 reduction and energy transduction remain controversial. Here, we reconstitute mammalian complex I into phospholipid nanodiscs with exogenous Q10. Using cryo-EM, we reveal a Q10 molecule occupying the full length of the Q-binding site in the 'active' (ready-to-go) resting state together with a matching substrate-free structure, and apply molecular dynamics simulations to propose how the charge states of key residues influence the Q10 binding pose. By comparing ligand-bound and ligand-free forms of the 'deactive' resting state (that require reactivating to catalyse), we begin to define how substrate binding restructures the deactive Q-binding site, providing insights into its physiological and mechanistic relevance.
    DOI:  https://doi.org/10.1038/s41467-022-30506-1
  3. Nat Struct Mol Biol. 2022 May;29(5): 415
    TALEDs complete the toolkit for editing human mitochondrial DNA.
    Carolina N Perdigoto.
      
    DOI:  https://doi.org/10.1038/s41594-022-00781-z
  4. J Cell Mol Med. 2022 May 18.
    Mitochondrial-derived vesicles: Recent insights.
    Lucia-Doina Popov.
      The generation of vesicles is a constitutive attribute of mitochondria inherited from bacterial ancestors. The physiological conditions and mild oxidative stress promote oxidation and dysfunction of certain proteins and lipids within the mitochondrial membranes; these constituents are subsequently packed as small mitochondrial-derived vesicles (MDVs) (70-150 nm in diameter) and are transported intracellularly to lysosomes and peroxisomes to be degraded. In this way, MDVs remove the damaged mitochondrial components, preserve mitochondrial structural and functional integrity and restore homeostasis. An outline of the current knowledge on MDVs seems to be necessary for understanding the potential impact of this research area in cellular (patho)physiology. The present synopsis is an attempt towards the accomplishment of this demand, highlighting also the still unclear issues related to MDVs. Here, we discuss (i) MDVs budding and generation (molecules and mechanisms), (ii) the distinct cargoes packed and transported by MDVs, (iii) the MDVs trafficking pathways and (iv) the biological role of MDVs, from quality controllers to the involvement in organellar crosstalk, mitochondrial antigen presentation and peroxisome de novo biogenesis. These complex roles uncover also mitochondria integration into the cellular environment. As the therapeutic exploitation of MDVs is currently limited, future insights into MDVs cell biology are expected to direct to novel diagnostic tools and treatments.
    Keywords:  PINK1; Parkin; Quality control; extracellular vesicles; lysosomes; peroxisome
    DOI:  https://doi.org/10.1111/jcmm.17391
  5. Front Mol Neurosci. 2022 ;15 867935
    Altered Mitochondrial Protein Homeostasis and Proteinopathies.
    Aya Jishi, Xin Qi.
      Increasing evidence implicates mitochondrial dysfunction as key in the development and progression of various forms of neurodegeneration. The multitude of functions carried out by mitochondria necessitates a tight regulation of protein import, dynamics, and turnover; this regulation is achieved via several, often overlapping pathways that function at different levels. The development of several major neurodegenerative diseases is associated with dysregulation of these pathways, and growing evidence suggests direct interactions between some pathogenic proteins and mitochondria. When these pathways are compromised, so is mitochondrial function, and the resulting deficits in bioenergetics, trafficking, and mitophagy can exacerbate pathogenic processes. In this review, we provide an overview of the regulatory mechanisms employed by mitochondria to maintain protein homeostasis and discuss the failure of these mechanisms in the context of several major proteinopathies.
    Keywords:  mitochondrial dysfunction; mitochondrial quality control; neurodegeneration; protein homeostasis; proteinopathies
    DOI:  https://doi.org/10.3389/fnmol.2022.867935
  6. Biomed J. 2022 May 11. pii: S2319-4170(22)00074-9. [Epub ahead of print]
    Targeting Mitochondrial bioenergetics as a promising therapeutic strategy in metabolic and neurodegenerative diseases.
    Gurjit Kaur Bhatti, Anshika Gupta, Paras Pahwa, Naina Khullar, Satwinder Singh, Umashanker Navik, Shashank Kumar, Sarabjit Singh Mastana, Arubala P Reddy, P Hemachandra Reddy, Jasvinder Singh Bhatti.
      Mitochondria are the organelles that generate energy for the cells and act as biosynthetic and bioenergetic factories, vital for normal cell functioning and human health. Mitochondrial bioenergetics is considered an important measure to assess the pathogenesis of various diseases. Dysfunctional mitochondria affect or cause several conditions involving the most energy-intensive organs, including the brain, muscles, heart, and liver. This dysfunction may be attributed to an alteration in mitochondrial enzymes, increased oxidative stress, impairment of electron transport chain and oxidative phosphorylation, or mutations in mitochondrial DNA that leads to the pathophysiology of various pathological conditions, including neurological and metabolic disorders. The drugs or compounds targeting mitochondria are considered more effective and safer for treating these diseases. In this review, we make an effort to concise the available literature on mitochondrial bioenergetics in various conditions and the therapeutic potential of various drugs/compounds targeting mitochondrial bioenergetics in metabolic and neurodegenerative diseases.
    Keywords:  Antioxidants; Bioenergetics; Electron transport chain; Mitochondrial dysfunction; Oxidative stress
    DOI:  https://doi.org/10.1016/j.bj.2022.05.002
  7. Biomed Pharmacother. 2022 May;pii: S0753-3322(22)00307-9. [Epub ahead of print]149 112918
    Are mitophagy enhancers therapeutic targets for Alzheimer's disease?
    Jangampalli Adi Pradeepkiran, Ashly Hindle, Sudhir Kshirsagar, P Hemachandra Reddy.
      Healthy mitochondria are essential for functional bioenergetics, calcium signaling, and balanced redox homeostasis. Dysfunctional mitochondria are a central aspect of aging and neurodegenerative diseases such as Alzheimer's disease (AD). The formation and accumulation of amyloid beta (Aβ) and hyperphosphorylated tau (P-tau) play large roles in the cellular changes seen in AD, including mitochondrial dysfunction, synaptic damage, neuronal loss, and defective mitophagy. Mitophagy is the cellular process whereby damaged mitochondria are selectively removed, and it plays an important role in mitochondrial quality control. Dysfunctional mitochondria are associated with increased reactive oxygen species and increased levels of Aβ, P-tau and Drp1, which together trigger mitophagy and autophagy. Impaired mitophagy causes the progressive accumulation of defective organelles and damaged mitochondria, and it has been hypothesized that the restoration of mitophagy may offer therapeutic benefits to AD patients. This review highlights the challenges of pharmacologically inducing mitophagy through two different signaling cascades: 1) The PINK1/parkin-dependent pathway and 2) the PINK1/parkin-independent pathway, with an emphasis on abnormal mitochondrial interactions with Aβ and P-Tau, which alter mitophagy in an age-dependent manner. This article also summarizes recent studies on the effects of mitophagy enhancers, including urolithin A, NAD+, actinonin, and tomatidine, on mutant APP/Aβ and mutant Tau. Findings from our lab have revealed that mitophagy enhancers can suppress APP/Aβ-induced and mutant Tau-induced mitochondrial and synaptic dysfunctions in mouse and cell line models of AD. Finally, we discuss the mechanisms underlying the beneficial health effects of mitophagy enhancers like urolithin A, NAD+, resveratrol and spermidine in AD.
    Keywords:  Alzheimer’s disease; Aβ; Mitochondrial dysfunction; Mitophagy; Phosphorylated tau
    DOI:  https://doi.org/10.1016/j.biopha.2022.112918
  8. Autophagy. 2022 May 19. 1-2
    SQSTM1 and its MAP1LC3B-binding domain induce forced mitophagy to degrade mitochondrial carryover during mitochondrial replacement therapy.
    Xiao-Yan Fan, Shen Yin, Shi-Ming Luo.
      Mitophagy is a process that selectively degrades mitochondria in cells, and it involves a series of signaling events. Our recent paper shows that the ectopic expression of SQSTM1 and its MAP1LC3B-binding domain (Binding) at the mitochondrial outer membrane, can directly cause mitophagy. To distinguish this mitophagy from others, we called it forced mitophagy. Further results show that the forced mitophagy can degrade half of the mitochondria and their DNA in HeLa cells and mouse embryos. Meanwhile, there are no apparent effects on mitochondrial membrane potential (MMP), reactive oxygen species (ROS), mitosis and embryo development. Thus, the forced mitophagy was examined to selectively degrade mitochondrial carryover in the nuclear donor embryos' mitochondria by pre-labeling with Binding before mitochondrial replacement therapy (MRT). The results show that the forced mitophagy can reduce mitochondrial carryover from an average of 4% to 0.09% compared to the controls in mouse embryos and tissues. In addition, the offspring from MRT mice show negligible effects on growth, reproduction, exercise and behavior. Furthermore, results from human tri-pronuclear embryos show that the forced mitophagy results in undetectable mitochondrial carryover in 77% of embryos following MRT. Therefore, forced mitophagy is efficient and safe for degrading mitochondrial carryover in MRT.
    Keywords:  Forced mitophagy; NIX; SQSTM1; mitochondrial carryover; mitochondrial replacement therapy
    DOI:  https://doi.org/10.1080/15548627.2022.2077552
  9. Cell Biosci. 2022 May 19. 12(1): 66
    Mitochondrial transfer/transplantation: an emerging therapeutic approach for multiple diseases.
    Zonghan Liu, Yi Sun, Zhengtang Qi, Lu Cao, Shuzhe Ding.
      Mitochondria play a pivotal role in energy generation and cellular physiological processes. These organelles are highly dynamic, constantly changing their morphology, cellular location, and distribution in response to cellular stress. In recent years, the phenomenon of mitochondrial transfer has attracted significant attention and interest from biologists and medical investigators. Intercellular mitochondrial transfer occurs in different ways, including tunnelling nanotubes (TNTs), extracellular vesicles (EVs), and gap junction channels (GJCs). According to research on intercellular mitochondrial transfer in physiological and pathological environments, mitochondrial transfer hold great potential for maintaining body homeostasis and regulating pathological processes. Multiple research groups have developed artificial mitochondrial transfer/transplantation (AMT/T) methods that transfer healthy mitochondria into damaged cells and recover cellular function. This paper reviews intercellular spontaneous mitochondrial transfer modes, mechanisms, and the latest methods of AMT/T. Furthermore, potential application value and mechanism of AMT/T in disease treatment are also discussed.
    Keywords:  Ageing; Cancer therapy; Energy metabolism; Mitochondrial transfer; Mitochondrial transplantation; Stem cell; Tissue injury; mtDNA mutations and deletions
    DOI:  https://doi.org/10.1186/s13578-022-00805-7
  10. Neurology. 2022 May 17. 98(20): 836-840
    What Is the Role of Mitochondrial Dysfunction in Programmed Axon Death?
    Eduardo Benarroch.
      
    DOI:  https://doi.org/10.1212/WNL.0000000000200691
  11. J Cachexia Sarcopenia Muscle. 2022 May 20.
    Ambra1 deficiency impairs mitophagy in skeletal muscle.
    Lisa Gambarotto, Samuele Metti, Martina Chrisam, Cristina Cerqua, Patrizia Sabatelli, Andrea Armani, Carlo Zanon, Marianna Spizzotin, Silvia Castagnaro, Flavie Strappazzon, Paolo Grumati, Matilde Cescon, Paola Braghetta, Eva Trevisson, Francesco Cecconi, Paolo Bonaldo.
      BACKGROUND: Maintaining healthy mitochondria is mandatory for muscle viability and function. An essential surveillance mechanism targeting defective and harmful mitochondria to degradation is the selective form of autophagy called mitophagy. Ambra1 is a multifaceted protein with well-known autophagic and mitophagic functions. However, the study of its role in adult tissues has been extremely limited due to the embryonic lethality caused by full-body Ambra1 deficiency.METHODS: To establish the role of Ambra1 as a positive regulator of mitophagy, we exploited in vivo overexpression of a mitochondria-targeted form of Ambra1 in skeletal muscle. To dissect the consequence of Ambra1 inactivation in skeletal muscle, we generated muscle-specific Ambra1 knockout (Ambra1fl/fl :Mlc1f-Cre) mice. Mitochondria-enriched fractions were obtained from muscles of fed and starved animals to investigate the dynamics of the mitophagic flux.
    RESULTS: Our data show that Ambra1 has a critical role in the mitophagic flux of adult murine skeletal muscle and that its genetic inactivation leads to mitochondria alterations and myofibre remodelling. Ambra1 overexpression in wild-type muscles is sufficient to enhance mitochondria clearance through the autophagy-lysosome system. Consistently with this, Ambra1-deficient muscles display an abnormal accumulation of the mitochondrial marker TOMM20 by +76% (n = 6-7; P < 0.05), a higher presence of myofibres with swollen mitochondria by +173% (n = 4; P < 0.05), and an alteration in the maintenance of the mitochondrial membrane potential and a 34% reduction in the mitochondrial respiratory complex I activity (n = 4; P < 0.05). Lack of Ambra1 in skeletal muscle leads to impaired mitophagic flux, without affecting the bulk autophagic process. This is due to a significantly decreased recruitment of DRP1 (n = 6-7 mice; P < 0.01) and Parkin (n = 6-7 mice; P < 0.05) to the mitochondrial compartment, when compared with controls. Ambra1-deficient muscles also show a marked dysregulation of the endolysosome compartment, as the incidence of myofibres with lysosomal accumulation is 20 times higher than wild-type muscles (n = 4; P < 0.05). Histologically, Ambra1-deficient muscles of both 3- and 6-month-old animals display a significant decrease of myofibre cross-sectional area and a 52% reduction in oxidative fibres (n = 6-7; P < 0.05), thus highlighting a role for Ambra1 in the proper structure and activity of skeletal muscle.
    CONCLUSIONS: Our study indicates that Ambra1 is critical for skeletal muscle mitophagy and for the proper maintenance of functional mitochondria.
    Keywords:  Ambra1; Mitochondria; Mitophagy; Skeletal muscle
    DOI:  https://doi.org/10.1002/jcsm.13010
  12. Clin Exp Immunol. 2022 May 16. pii: uxac053. [Epub ahead of print]
    Metabolites: Fuelling the Immune Response.
    Corrado Mauro, Diana Moreira, Nicholas Jones.
      
    DOI:  https://doi.org/10.1093/cei/uxac053
  13. Neurobiol Dis. 2022 May 13. pii: S0969-9961(22)00145-0. [Epub ahead of print]170 105753
    Neuron-astrocyte transmitophagy is altered in Alzheimer's disease.
    Riikka Lampinen, Irina Belaya, Liudmila Saveleva, Jeffrey R Liddell, Dzhessi Rait, Mikko T Huuskonen, Raisa Giniatullina, Annika Sorvari, Liisi Soppela, Nikita Mikhailov, Isabella Boccuni, Rashid Giniatullin, Marcela Cruz-Haces, Julia Konovalova, Marja Koskuvi, Andrii Domanskyi, Riikka H Hämäläinen, Gundars Goldsteins, Jari Koistinaho, Tarja Malm, Sweelin Chew, Kirsi Rilla, Anthony R White, Nicholas Marsh-Armstrong, Katja M Kanninen.
      Under physiological conditions in vivo astrocytes internalize and degrade neuronal mitochondria in a process called transmitophagy. Mitophagy is widely reported to be impaired in neurodegeneration but it is unknown whether and how transmitophagy is altered in Alzheimer's disease (AD). Here we report that the internalization of neuronal mitochondria is significantly increased in astrocytes isolated from AD mouse brains. We also demonstrate that the degradation of neuronal mitochondria by astrocytes is increased in AD mice at the age of 6 months onwards. Furthermore, we demonstrate for the first time a similar phenomenon between human neurons and AD astrocytes, and in murine hippocampi in vivo. The results suggest the involvement of S100a4 in impaired mitochondrial transfer between neurons and AD astrocytes together with significant increases in the mitophagy regulator and reactive oxygen species in aged AD astrocytes. These findings demonstrate altered neuron-supporting functions of AD astrocytes and provide a starting point for studying the molecular mechanisms of transmitophagy in AD.
    Keywords:  Alzheimer's disease; Astrocytes; Mitochondria; Mitophagy; Transmitophagy
    DOI:  https://doi.org/10.1016/j.nbd.2022.105753
  14. Methods Mol Biol. 2022 May 18.
    Genome Engineering Human ESCs or iPSCs with Cytosine and Adenine Base Editors.
    Giulia Pavani, Joshua G Klein, Deborah L French, Paul Gadue.
      The ability to engineer specific mutations in human embryonic stem cells (ECSs) or induced pluripotent stem cells (iPSCs) is extremely important in the modeling of human diseases and the study of biological processes. While CRISPR/Cas9 can robustly generate gene knockouts (KOs) and gene loci modifications in coding sequences of iPSCs, it remains difficult to produce monoallelic mutations or modify specific nucleotides in noncoding sequences due to technical constraints.Here, we describe how to leverage cytosine (BE4max) and adenine (ABEmax) base editors to introduce precise mutations in iPSCs without inducing DNA double-stranded breaks. This chapter illustrates how to design and clone gRNAs, evaluate editing efficiency, and detect genomic edits at specific sites in iPSCs through the utilization of base editing technology.
    Keywords:  Base editing; Disease modeling; Gene correction; Genome editing; Induced pluripotent stem cells (iPSC)
    DOI:  https://doi.org/10.1007/7651_2022_461
  15. Front Neurosci. 2022 ;16 874768
    Simultaneous Quantification of Mitochondrial Mature Frataxin and Extra-Mitochondrial Frataxin Isoform E in Friedreich's Ataxia Blood.
    Qingqing Wang, Laurent Laboureur, Liwei Weng, Nicolas M Eskenazi, Lauren A Hauser, Clementina Mesaros, David R Lynch, Ian A Blair.
      Friedreich's ataxia (FRDA) is an autosomal recessive disease caused by an intronic guanine-adenine-adenine (GAA) triplet expansion in the frataxin (FXN) gene, which leads to reduced expression of full-length frataxin (1-210) also known as isoform 1. Full-length frataxin has a mitochondrial targeting sequence, which facilitates its translocation into mitochondria where it is processed through cleavage at G41-L42 and K80-S81 by mitochondrial processing (MPP) to release mitochondrial mature frataxin (81-210). Alternative splicing of FXN also leads to expression of N-terminally acetylated extra-mitochondrial frataxin (76-210) named isoform E because it was discovered in erythrocytes. Frataxin isoforms are undetectable in serum or plasma, and originally whole blood could not be used as a biomarker in brief therapeutic trials because it is present in erythrocytes, which have a half-life of 115-days and so frataxin levels would remain unaltered. Therefore, an assay was developed for analyzing frataxin in platelets, which have a half-life of only 10-days. However, our discovery that isoform E is only present in erythrocytes, whereas, mature frataxin is present primarily in short-lived peripheral blood mononuclear cells (PBMCs), granulocytes, and platelets, meant that both proteins could be quantified in whole blood samples. We now report a quantitative assay for frataxin proteoforms in whole blood from healthy controls and FRDA patients. The assay is based on stable isotope dilution coupled with immunoprecipitation (IP) and two-dimensional-nano-ultrahigh performance liquid chromatography/parallel reaction monitoring/high resolution mass spectrometry (2D-nano-UHPLC-PRM/HRMS). The lower limit of quantification was 0.5 ng/mL for each proteoform and the assays had 100% sensitivity and specificity for discriminating between healthy controls (n = 11) and FRDA cases (N = 100 in year-1, N = 22 in year-2,3). The mean levels of mature frataxin in whole blood from healthy controls and homozygous FRDA patients were significantly different (p < 0.0001) at 7.5 ± 1.5 ng/mL and 2.1 ± 1.2 ng/mL, respectively. The mean levels of isoform E in whole blood from healthy controls and homozygous FRDA patients were significantly different (p < 0.0001) at 26.8 ± 4.1 ng/mL and 4.7 ± 3.3 ng/mL, respectively. The mean levels of total frataxin in whole blood from healthy controls and homozygous FRDA patients were significantly different (p < 0.0001) at 34.2 ± 4.3 ng/mL and 6.8 ± 4.0 ng/mL, respectively. The assay will make it possible to rigorously monitor the natural history of the disease and explore the potential role of isoform E in etiology of the disease. It will also facilitate the assessment of therapeutic interventions (including gene therapy approaches) that attempt to increase frataxin protein expression as a treatment for this devastating disease.
    Keywords:  assay validations; heterozygous Friedreich’s ataxia; homozygous Friedreich’s ataxia; liquid chromatography; mass spectrometry; neurodegenerative disease; stable isotope dilution
    DOI:  https://doi.org/10.3389/fnins.2022.874768
  16. Neurologia (Engl Ed). 2022 May;pii: S2173-5808(21)00048-1. [Epub ahead of print]37(4): 257-262
    Autosomal recessive spinocerebellar ataxia SCAR8/ARCA1: first families detected in Spain.
    M Arias, P Mir, M Fernández-Matarrubia, J Arpa, R García-Ramos, P Blanco-Arias, B Quintans, M J Sobrido.
      INTRODUCTION: Autosomal recessive spinocerebellar ataxia type 8 (ARCA1/SCAR8) is caused by mutations of the SYNE1 gene. The disease was initially described in families from Quebec (Canada) with a phenotype of pure cerebellar syndrome, but in recent years has been reported with a more variable clinical phenotype in other countries. Cases have recently been described of muscular dystrophy, arthrogryposis, and cardiomyopathy due to SYNE1 mutations.OBJECTIVE: To describe clinical and molecular findings from 4 patients (3 men and one woman) diagnosed with ARCA1/SCAR8 from 3 Spanish families from different regions.
    MATERIAL AND METHODS: We describe the clinical, paraclinical, and genetic results from 4 patients diagnosed with ARCA1/SCAR8 at different Spanish neurology departments.
    RESULTS: Onset occurred in the third or fourth decade of life in all patients. After 15 years of progression, 3 patients presented pure cerebellar syndrome, similar to the Canadian patients; the fourth patient, with over 30 years' progression, presented vertical gaze palsy, pyramidal signs, and moderate cognitive impairment. In all patients, MRI studies showed cerebellar atrophy. The genetic study revealed distinct pathogenic SYNE1 mutations in each family.
    CONCLUSIONS: ARCA1/SCAR8 can be found worldwide and may be caused by many distinct mutations in the SYNE1 gene. The disease may manifest with a complex phenotype of varying severity.
    Keywords:  ARCA1; Ataxia; Autosomal recessive inheritance; Gene panel; Herencia autosómica recesiva; Panel de genes; SCAR8; SYNE1; Secuenciación; Sequencing
    DOI:  https://doi.org/10.1016/j.nrleng.2019.01.014
  17. Bio Protoc. 2022 Mar 05. 12(5): e4347
    Labeling and Tracking Mitochondria with Photoactivation in Drosophila Embryos.
    Sayali Chowdhary, Richa Rikhy.
      Mitochondria are relatively small, fragmented, and abundant in the large embryos of Drosophila, Xenopus and zebrafish. It is essential to study their distribution and dynamics in these embryos to understand the mechanistic role of mitochondrial function in early morphogenesis events. Photoactivation of mitochondrially tagged GFP (mito-PA-GFP) is an attractive method to highlight a specific population of mitochondria in living embryos and track their distribution during development. Drosophila embryos contain large numbers of maternally inherited mitochondria, which distribute differently at specific stages of early embryogenesis. They are enriched basally in the syncytial division cycles and move apically during cellularization. Here, we outline a method for highlighting a population of mitochondria in discrete locations using mito-PA-GFP in the Drosophila blastoderm embryo, to follow their distribution across syncytial division cycles and cellularization. Photoactivation uses fluorophores, such as PA-GFP, that can change their fluorescence state upon exposure to ultraviolet light. This enables marking a precise population of fluorescently tagged molecules of organelles at selected regions, to visualize and systematically follow their dynamics and movements. Photoactivation followed by live imaging provides an effective way to pulse label a population of mitochondria and follow them through the dynamic morphogenetic events during Drosophila embryogenesis.
    Keywords:  Blastoderm; Drosophila; Embryogenesis; Mitochondria; Photoactivation
    DOI:  https://doi.org/10.21769/BioProtoc.4347
  18. Nat Commun. 2022 May 19. 13(1): 2769
    Mitochondrial calcium uniporter stabilization preserves energetic homeostasis during Complex I impairment.
    Enrique Balderas, David R Eberhardt, Sandra Lee, John M Pleinis, Salah Sommakia, Anthony M Balynas, Xue Yin, Mitchell C Parker, Colin T Maguire, Scott Cho, Marta W Szulik, Anna Bakhtina, Ryan D Bia, Marisa W Friederich, Timothy M Locke, Johan L K Van Hove, Stavros G Drakos, Yasemin Sancak, Martin Tristani-Firouzi, Sarah Franklin, Aylin R Rodan, Dipayan Chaudhuri.
      Calcium entering mitochondria potently stimulates ATP synthesis. Increases in calcium preserve energy synthesis in cardiomyopathies caused by mitochondrial dysfunction, and occur due to enhanced activity of the mitochondrial calcium uniporter channel. The signaling mechanism that mediates this compensatory increase remains unknown. Here, we find that increases in the uniporter are due to impairment in Complex I of the electron transport chain. In normal physiology, Complex I promotes uniporter degradation via an interaction with the uniporter pore-forming subunit, a process we term Complex I-induced protein turnover. When Complex I dysfunction ensues, contact with the uniporter is inhibited, preventing degradation, and leading to a build-up in functional channels. Preventing uniporter activity leads to early demise in Complex I-deficient animals. Conversely, enhancing uniporter stability rescues survival and function in Complex I deficiency. Taken together, our data identify a fundamental pathway producing compensatory increases in calcium influx during Complex I impairment.
    DOI:  https://doi.org/10.1038/s41467-022-30236-4
  19. Nat Commun. 2022 May 16. 13(1): 2706
    Identification of a modulator of the actin cytoskeleton, mitochondria, nutrient metabolism and lifespan in yeast.
    Cierra N Sing, Enrique J Garcia, Thomas G Lipkin, Thomas M Huckaba, Catherine A Tsang, Arielle C Coughlin, Emily J Yang, Istvan R Boldogh, Ryo Higuchi-Sanabria, Liza A Pon.
      In yeast, actin cables are F-actin bundles that are essential for cell division through their function as tracks for cargo movement from mother to daughter cell. Actin cables also affect yeast lifespan by promoting transport and inheritance of higher-functioning mitochondria to daughter cells. Here, we report that actin cable stability declines with age. Our genome-wide screen for genes that affect actin cable stability identified the open reading frame YKL075C. Deletion of YKL075C results in increases in actin cable stability and abundance, mitochondrial fitness, and replicative lifespan. Transcriptome analysis revealed a role for YKL075C in regulating branched-chain amino acid (BCAA) metabolism. Consistent with this, modulation of BCAA metabolism or decreasing leucine levels promotes actin cable stability and function in mitochondrial quality control. Our studies support a role for actin stability in yeast lifespan, and demonstrate that this process is controlled by BCAA and a previously uncharacterized ORF YKL075C, which we refer to as actin, aging and nutrient modulator protein 1 (AAN1).
    DOI:  https://doi.org/10.1038/s41467-022-30045-9
  20. Sci Rep. 2022 May 19. 12(1): 8356
    Identification of adeno-associated virus variants for gene transfer into human neural cell types by parallel capsid screening.
    Lea Jessica Flitsch, Kathleen Börner, Christian Stüllein, Simon Ziegler, Vera Sonntag-Buck, Ellen Wiedtke, Vesselina Semkova, Si Wah Christina Au Yeung, Julia Schlee, Mohamad Hajo, Mona Mathews, Beatrice Stefanie Ludwig, Susanne Kossatz, Horst Kessler, Dirk Grimm, Oliver Brüstle.
      Human brain cells generated by in vitro cell programming provide exciting prospects for disease modeling, drug discovery and cell therapy. These applications frequently require efficient and clinically compliant tools for genetic modification of the cells. Recombinant adeno-associated viruses (AAVs) fulfill these prerequisites for a number of reasons, including the availability of a myriad of AAV capsid variants with distinct cell type specificity (also called tropism). Here, we harnessed a customizable parallel screening approach to assess a panel of natural or synthetic AAV capsid variants for their efficacy in lineage-related human neural cell types. We identified common lead candidates suited for the transduction of directly converted, early-stage induced neural stem cells (iNSCs), induced pluripotent stem cell (iPSC)-derived later-stage, radial glia-like neural progenitors, as well as differentiated astrocytic and mixed neuroglial cultures. We then selected a subset of these candidates for functional validation in iNSCs and iPSC-derived astrocytes, using shRNA-induced downregulation of the citrate transporter SLC25A1 and overexpression of the transcription factor NGN2 for proofs-of-concept. Our study provides a comparative overview of the susceptibility of different human cell programming-derived brain cell types to AAV transduction and a critical discussion of the assets and limitations of this specific AAV capsid screening approach.
    DOI:  https://doi.org/10.1038/s41598-022-12404-0
  21. Sci Rep. 2022 May 18. 12(1): 8324
    Association between sperm mitochondrial DNA copy number and deletion rate and industrial air pollution dynamics.
    Miluse Vozdova, Svatava Kubickova, Vera Kopecka, Jaroslav Sipek, Jiri Rubes.
      The effects of air pollution on men's reproductive health can be monitored by evaluating semen quality and sperm DNA damage. We used real-time PCR to analyse the effects of air pollution on sperm mitochondrial DNA copy number (mtDNAcn) and deletion (mtDNAdel) rates in semen samples collected from 54 men in two seasons with different levels of industrial and traffic air pollution. MtDNAdel rates were significantly higher following the high exposure period and were positively correlated with mtDNAcn. However, we did not find any difference in mtDNAcn between the two seasons. MtDNAcn was positively correlated with the DNA fragmentation index and the rates of sperm with chromatin condensation defects, previously assessed by sperm chromatin structure assay, and negatively correlated with sperm concentration, progressive motility, viability, and normal morphology. This indicates that mtDNAcn is more closely associated with male fertility than mtDNAdel rates. In contrast, mtDNAdel might be a more sensitive biomarker of air pollution exposure in urban industrial environments.
    DOI:  https://doi.org/10.1038/s41598-022-12328-9
  22. Front Aging Neurosci. 2022 ;14 875989
    Age-Dependent Alterations of Cognition, Mitochondrial Function, and Beta-Amyloid Deposition in a Murine Model of Alzheimer's Disease-A Longitudinal Study.
    Martina Reutzel, Rekha Grewal, Aljoscha Joppe, Gunter P Eckert.
      Aging is the main risk factor for sporadic Alzheimer's disease (AD), which is characterized by the cerebral deposition of β-amyloid peptides (Aβ) and cognitive decline. Mitochondrial dysfunction is also characteristic of the disease and represents a hallmark of both, aging and neurodegeneration. We longitudinally followed Aβ levels, cognition, and mitochondrial function in the same cohort of Thy1-APP751SL mice representing a murine model of AD. In the course of time, changes were most prominent at an age of 13 months including the latency time in the passive avoidance test, the activity of complexes I and IV of the mitochondrial respiration chain, and expression of genes related to mitochondrial biogenesis and synaptic plasticity including Peroxisome proliferator-activated receptor gamma coactivator 1-alpha (PGC1-α), CAMP responsive element binding protein 1 (CREB1), and Synaptophysin 1 (SYP1). These changes occurred in parallel with massively increasing cerebral Aβ levels. Other parameters were changed in younger mice including the alteration rate in the Y-maze test and the nesting score when Aβ levels were not changed yet. The results are consistent in the cohort described. However, previous, non-longitudinal studies reported divergent time points for the occurrence of the parameters studied. These findings are discussed in light of the current results.
    Keywords:  Alzheimers’s disease; amyloid-beta; longitudinal studies; mitochondrial dysfunction; transgenic mouse models
    DOI:  https://doi.org/10.3389/fnagi.2022.875989
  23. Nat Commun. 2022 May 19. 13(1): 2760
    Lipid droplet degradation by autophagy connects mitochondria metabolism to Prox1-driven expression of lymphatic genes and lymphangiogenesis.
    Odeta Meçe, Diede Houbaert, Maria-Livia Sassano, Tania Durré, Hannelore Maes, Marco Schaaf, Sanket More, Maarten Ganne, Melissa García-Caballero, Mila Borri, Jelle Verhoeven, Madhur Agrawal, Kathryn Jacobs, Gabriele Bergers, Silvia Blacher, Bart Ghesquière, Mieke Dewerchin, Johan V Swinnen, Stefan Vinckier, María S Soengas, Peter Carmeliet, Agnès Noël, Patrizia Agostinis.
      Autophagy has vasculoprotective roles, but whether and how it regulates lymphatic endothelial cells (LEC) homeostasis and lymphangiogenesis is unknown. Here, we show that genetic deficiency of autophagy in LEC impairs responses to VEGF-C and injury-driven corneal lymphangiogenesis. Autophagy loss in LEC compromises the expression of main effectors of LEC identity, like VEGFR3, affects mitochondrial dynamics and causes an accumulation of lipid droplets (LDs) in vitro and in vivo. When lipophagy is impaired, mitochondrial ATP production, fatty acid oxidation, acetyl-CoA/CoA ratio and expression of lymphangiogenic PROX1 target genes are dwindled. Enforcing mitochondria fusion by silencing dynamin-related-protein 1 (DRP1) in autophagy-deficient LEC fails to restore LDs turnover and lymphatic gene expression, whereas supplementing the fatty acid precursor acetate rescues VEGFR3 levels and signaling, and lymphangiogenesis in LEC-Atg5-/- mice. Our findings reveal that lipophagy in LEC by supporting FAO, preserves a mitochondrial-PROX1 gene expression circuit that safeguards LEC responsiveness to lymphangiogenic mediators and lymphangiogenesis.
    DOI:  https://doi.org/10.1038/s41467-022-30490-6
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