bims-mitmed Biomed News
on Mitochondrial medicine
Issue of 2023‒11‒05
27 papers selected by
Dario Brunetti, Fondazione IRCCS Istituto Neurologico 

  1. Science. 2023 Nov 02. eadf4154
      Mitochondria must maintain adequate amounts of metabolites for protective and biosynthetic functions. However, how mitochondria sense the abundance of metabolites and regulate metabolic homeostasis is not well understood. We focused on glutathione (GSH), a critical redox metabolite in mitochondria and identified a feedback mechanism that controls its abundance through the mitochondrial GSH transporter, SLC25A39. Under physiological conditions, SLC25A39 is rapidly degraded by a mitochondrial protease, AFG3L2. Depletion of GSH dissociates AFG3L2 from SLC25A39, causing a compensatory increase in mitochondrial GSH uptake. Genetic and proteomic analysis identified a putative iron-sulfur cluster in the matrix-facing loop of SLC25A39 to be essential for this regulation, coupling mitochondrial iron homeostasis to GSH import. Altogether, our work revealed a paradigm for the autoregulatory control of metabolic homeostasis in organelles.
  2. Acta Diabetol. 2023 Oct 31.
      AIMS: The most common pathogenic mitochondrial mutation associated with mitochondrial disease is m.3243A>G. Increased obstetric complications, such as spontaneous abortion, gestational diabetes (GDM), preterm delivery, and preeclampsia, have been reported in women carrying this mutation. We aimed to determine the fetal and maternal outcomes in pregnant women with mitochondrial disease.METHODS: We retrospectively studied the obstetric and perinatal outcomes in 88 pregnancies of 26 women with genetically confirmed mitochondrial disease (m.3243A>G in the MTTL1 gene (n = 25); m.12258C>A in the MT-TS2 gene (n = 1)). Outcomes included pregnancy related complications, mode of delivery, gestational age at delivery and birthweight.
    RESULTS: Mean heteroplasmy rate was 18%. The miscarriage rate was higher than background at 25%. 21 pregnancies (24%) were complicated by GDM; 9 pregnancies (13.6%) had a preterm delivery and 2 of them (3%) an extreme premature delivery < 32 weeks. One woman had preeclampsia and one had a postpartum hemorrhage. The caesarean section (CS) rate was 20%. For every unit increase in maternal heteroplasmy levels there was a 26% increased risk of undergoing an assisted operative vaginal delivery (OR 1.26, 95% CI 1.04-1.53, P = 0.002, Bonferroni corrected P = 0.005) and an 18% increased risk of undergoing a CS (OR 1.18, 95% CI 1.01-1.39, P = 0.01, Bonferroni corrected P = 0.03) compared to a spontaneous vaginal delivery. There was a statistical significant correlation between maternal and offspring heteroplasmy levels. Spearman correlation rho = 0.96, 95% CI 0.78-0.99, P = 0.0002.
    CONCLUSION: Women with mitochondrial disease appear to have more frequent obstetric complications including miscarriage and GDM. Pre-pregnancy diagnosis of m.3243A>G will enable the counseling of women and increase awareness of possible obstetric complications.
    Keywords:  Complications; Diabetes; Gestation; Heteroplasmy; Mitochondrial; m.3243A>G
  3. Trends Cell Biol. 2023 Oct 31. pii: S0962-8924(23)00207-6. [Epub ahead of print]
      Stem cells persist throughout the lifespan to repair and regenerate tissues due to their unique ability to self-renew and differentiate. Here we reflect on the recent discoveries in stem cells that highlight a mitochondrial metabolic checkpoint at the restriction point of the stem cell cycle. Mitochondrial activation supports stem cell proliferation and differentiation by providing energy supply and metabolites as signaling molecules. Concomitant mitochondrial stress can lead to loss of stem cell self-renewal and requires the surveillance of various mitochondrial quality control mechanisms. During aging, a mitochondrial protective program mediated by several sirtuins becomes dysregulated and can be targeted to reverse stem cell aging and tissue degeneration, giving hope for targeting the mitochondrial metabolic checkpoint for treating tissue degenerative diseases.
    Keywords:  NAD; NLRP3; SIRT2; SIRT3; SIRT7; aging
  4. Expert Opin Ther Targets. 2023 Oct 30. 1-4
    Keywords:  Aging; Extracellular Mitochondria; Hallmarks of Aging; Health; Healthy Longevity; Induced Pluripotent Stem Cells (iPSCs); Longevity; Mitochondria; Mitochondrial DNA (mtDNA); Mitochondrial Transfer; Mitochondrial Transplant; Rejuvenation; Senescent Cells; Telomeres
  5. Elife. 2023 Nov 01. pii: e84235. [Epub ahead of print]12
      Cardiac muscle has the highest mitochondrial density of any human tissue, but mitochondrial dysfunction is not a recognized cause of isolated cardiomyopathy. Here, we determined that the rare mitofusin (MFN) 2 R400Q mutation is 15-20× over-represented in clinical cardiomyopathy, whereas this specific mutation is not reported as a cause of MFN2 mutant-induced peripheral neuropathy, Charcot-Marie-Tooth disease type 2A (CMT2A). Accordingly, we interrogated the enzymatic, biophysical, and functional characteristics of MFN2 Q400 versus wild-type and CMT2A-causing MFN2 mutants. All MFN2 mutants had impaired mitochondrial fusion, the canonical MFN2 function. Compared to MFN2 T105M that lacked catalytic GTPase activity and exhibited normal activation-induced changes in conformation, MFN2 R400Q and M376A had normal GTPase activity with impaired conformational shifting. MFN2 R400Q did not suppress mitochondrial motility, provoke mitochondrial depolarization, or dominantly suppress mitochondrial respiration like MFN2 T105M. By contrast to MFN2 T105M and M376A, MFN2 R400Q was uniquely defective in recruiting Parkin to mitochondria. CRISPR editing of the R400Q mutation into the mouse Mfn2 gene induced perinatal cardiomyopathy with no other organ involvement; knock-in of Mfn2 T105M or M376V did not affect the heart. RNA sequencing and metabolomics of cardiomyopathic Mfn2 Q/Q400 hearts revealed signature abnormalities recapitulating experimental mitophagic cardiomyopathy. Indeed, cultured cardiomyoblasts and in vivo cardiomyocytes expressing MFN2 Q400 had mitophagy defects with increased sensitivity to doxorubicin. MFN2 R400Q is the first known natural mitophagy-defective MFN2 mutant. Its unique profile of dysfunction evokes mitophagic cardiomyopathy, suggesting a mechanism for enrichment in clinical cardiomyopathy.
    Keywords:  cardiomyopathy; developmental biology; heart; mitochondria; mitofusins; mouse
  6. Trends Cell Biol. 2023 Oct 30. pii: S0962-8924(23)00208-8. [Epub ahead of print]
      Mitochondria perform crucial functions in cellular metabolism, protein and lipid biogenesis, quality control, and signaling. The systematic analysis of protein complexes and interaction networks provided exciting insights into the structural and functional organization of mitochondria. Most mitochondrial proteins do not act as independent units, but are interconnected by stable or dynamic protein-protein interactions. Protein translocases are responsible for importing precursor proteins into mitochondria and form central elements of several protein interaction networks. These networks include molecular chaperones and quality control factors, metabolite channels and respiratory chain complexes, and membrane and organellar contact sites. Protein translocases link the distinct networks into an overarching network, the mitochondrial import network (MitimNet), to coordinate biogenesis, membrane organization and function of mitochondria.
    Keywords:  cell organelles; energetics; metabolism; mitochondria; morphology; protein assembly; protein networks; protein sorting
  7. bioRxiv. 2023 Oct 20. pii: 2023.10.19.563195. [Epub ahead of print]
      Ubiquitination of mitochondrial proteins provides a basis for the downstream recruitment of mitophagy machinery, yet whether ubiquitination of the machinery itself contributes to mitophagy is unknown. Here, we show that K63-linked polyubiquitination of the key mitophagy regulator TBK1 is essential for its mitophagy functions. This modification is catalyzed by the ubiquitin ligase TRIM5α. Mitochondrial damage triggers TRIM5α's auto-ubiquitination and its interaction with ubiquitin-binding autophagy adaptors including NDP52, optineurin, and NBR1. Autophagy adaptors, along with TRIM27, enable TRIM5α to engage with TBK1. TRIM5α with intact ubiquitination function is required for the proper accumulation of active TBK1 on damaged mitochondria in Parkin-dependent and Parkin-independent mitophagy pathways. Additionally, we show that TRIM5α can directly recruit autophagy initiation machinery to damaged mitochondria. Our data support a model in which TRIM5α provides a self-amplifying, mitochondria-localized, ubiquitin-based, assembly platform for TBK1 and mitophagy adaptors that is ultimately required to recruit the core autophagy machinery.
  8. J Cell Biol. 2023 Dec 04. pii: e202305032. [Epub ahead of print]222(12):
      Live super-resolution microscopy has allowed for new insights into recently identified mitochondria-lysosome contact sites, which mediate crosstalk between mitochondria and lysosomes, including co-regulation of Rab7 GTP hydrolysis and Drp1 GTP hydrolysis. Here, we highlight recent findings and future perspectives on this dynamic pathway and its roles in health and disease.
  9. Sci Adv. 2023 11 03. 9(44): eadh2584
      The γ-aminobutyric acid-mediated (GABAergic) system participates in many aspects of organismal physiology and disease, including proteostasis, neuronal dysfunction, and life-span extension. Many of these phenotypes are also regulated by reactive oxygen species (ROS), but the redox mechanisms linking the GABAergic system to these phenotypes are not well defined. Here, we report that GABAergic redox signaling cell nonautonomously activates many stress response pathways in Caenorhabditis elegans and enhances vulnerability to proteostasis disease in the absence of oxidative stress. Cell nonautonomous redox activation of the mitochondrial unfolded protein response (mitoUPR) proteostasis network requires UNC-49, a GABAA receptor that we show is activated by hydrogen peroxide. MitoUPR induction by a spinocerebellar ataxia type 3 (SCA3) C. elegans neurodegenerative disease model was similarly dependent on UNC-49 in C. elegans. These results demonstrate a multi-tissue paradigm for redox signaling in the GABAergic system that is transduced via a GABAA receptor to function in cell nonautonomous regulation of health, proteostasis, and disease.
  10. Cell Rep. 2023 Nov 01. pii: S2211-1247(23)01388-8. [Epub ahead of print]42(11): 113376
      Dysregulation of mitochondrial lipidome is associated with several human pathologies. Sun et al.1 show that LPGAT1 cooperates with TIMM14 to regulate phosphatidylglycerol transport from the endoplasmic reticulum to the mitochondria, and uncover the involvement of LPGAT1 deficiency in MEGDEL syndrome.
  11. Sci Rep. 2023 Nov 01. 13(1): 18822
      A Kinase Interacting Protein 1 (AKIP1) is a signalling adaptor that promotes mitochondrial respiration and attenuates mitochondrial oxidative stress in cultured cardiomyocytes. We sought to determine whether AKIP1 influences mitochondrial function and the mitochondrial adaptation in response to exercise in vivo. We assessed mitochondrial respiratory capacity, as well as electron microscopy and mitochondrial targeted-proteomics in hearts from mice with cardiomyocyte-specific overexpression of AKIP1 (AKIP1-TG) and their wild type (WT) littermates. These parameters were also assessed after four weeks of voluntary wheel running. In contrast to our previous in vitro study, respiratory capacity measured as state 3 respiration on palmitoyl carnitine was significantly lower in AKIP1-TG compared to WT mice, whereas state 3 respiration on pyruvate remained unaltered. Similar findings were observed for maximal respiration, after addition of FCCP. Mitochondrial DNA damage and oxidative stress markers were not elevated in AKIP1-TG mice and gross mitochondrial morphology was similar. Mitochondrial targeted-proteomics did reveal reductions in mitochondrial proteins involved in energy metabolism. Exercise performance was comparable between genotypes, whereas exercise-induced cardiac hypertrophy was significantly increased in AKIP1-TG mice. After exercise, mitochondrial state 3 respiration on pyruvate substrates was significantly lower in AKIP1-TG compared with WT mice, while respiration on palmitoyl carnitine was not further decreased. This was associated with increased mitochondrial fission on electron microscopy, and the activation of pathways associated with mitochondrial fission and mitophagy. This study suggests that AKIP1 regulates the mitochondrial proteome involved in energy metabolism and promotes mitochondrial turnover after exercise. Future studies are required to unravel the mechanistic underpinnings and whether the mitochondrial changes are required for the AKIP1-induced physiological cardiac growth.
  12. Biochim Biophys Acta Mol Basis Dis. 2023 Oct 30. pii: S0925-4439(23)00286-7. [Epub ahead of print] 166920
      Nervous system processes, including cognition and affective state, fundamentally rely on mitochondria. Impaired mitochondrial function is evident in major depressive disorder (MDD), reflecting cumulative detrimental influences of both extrinsic and intrinsic stressors, genetic predisposition, and mutation. Glucocorticoid 'stress' pathways converge on mitochondria; oxidative and nitrosative stresses in MDD are largely mitochondrial in origin; both initiate cascades promoting mitochondrial DNA (mtDNA) damage with disruptions to mitochondrial biogenesis and tryptophan catabolism. Mitochondrial dysfunction facilitates proinflammatory dysbiosis while directly triggering immuno-inflammatory activation via released mtDNA, mitochondrial lipids and mitochondria associated membranes (MAMs), further disrupting mitochondrial function and mitochondrial quality control, promoting the accumulation of abnormal mitochondria (confirmed in autopsy studies). Established and putative mechanisms highlight a mitochondrial nexus within the psycho-immune neuroendocrine (PINE) network implicated in MDD. Whether lowering neuronal resilience and thresholds for disease, or linking mechanistic nodes within the MDD pathogenic network, impaired mitochondrial function emerges as an important risk, a functional biomarker, providing a therapeutic target in MDD. Several treatment modalities have been demonstrated to reset mitochondrial function, which could benefit those with MDD.
    Keywords:  Adipokines; Chronic stress; Inflammasome; Major depressive disorder; Mitochondria; Neuroendocrine
  13. Mol Genet Metab. 2023 Oct 20. pii: S1096-7192(23)00340-2. [Epub ahead of print] 107710
      Iron‑sulfur clusters (FeS) are one of the most primitive and ubiquitous cofactors used by various enzymes in multiple pathways. Biosynthesis of FeS is a complex multi-step process that is tightly regulated and requires multiple machineries. IBA57, along with ISCA1 and ISCA2, play a role in maturation of [4Fe-4S] clusters which are required for multiple mitochondrial enzymes including mitochondrial Complex I, Complex II, lipoic acid synthase, and aconitase. Pathogenic variants in IBA57 have been associated with multiple mitochondrial dysfunctions syndrome 3 (MMDS3) characterized by infantile to early childhood-onset psychomotor regression, optic atrophy and nonspecific dysmorphism. Here we report a female proband who had prenatal involvement including IUGR and microcephaly and developed subacute psychomotor regression at the age of 5 weeks in the setting of preceding viral infection. Brain imaging revealed cortical malformation with polymicrogyria and abnormal signal alteration in brainstem and spinal cord. Biochemical analysis revealed increased plasma glycine and hyperexcretion of multiple organic acids in urine, raising the concern for lipoic acid biosynthesis defects and mitochondrial FeS assembly defects. Molecular analysis subsequently detected compound heterozygous variants in IBA57, confirming the diagnosis of MMDS3. Although the number of MMDS3 patients are limited, certain degree of genotype-phenotype correlation has been observed. Unusual brain imaging in the proband highlights the need to include mitochondrial disorders as differential diagnoses of structural brain abnormalities. Lastly, in addition to previously known biomarkers including high blood lactate and plasma glycine levels, the increase of 2-hydroxyadipic and 2-ketoadipic acids in urine organic acid analysis, in the appropriate clinical context, should prompt an evaluation for the lipoic acid biosynthesis defects and mitochondrial FeS assembly defects.
    Keywords:  IBA57; Iron‑sulfur clusters; Lysine metabolism; Mitochondrial disorder; Rhabdomyolysis
  14. Front Neurosci. 2023 ;17 1268883
      Ensuring mitochondrial quality is essential for maintaining neuronal homeostasis, and mitochondrial transport plays a vital role in mitochondrial quality control. In this review, we first provide an overview of neuronal mitochondrial transport, followed by a detailed description of the various motors and adaptors associated with the anterograde and retrograde transport of mitochondria. Subsequently, we review the modest evidence involving mitochondrial transport mechanisms that has surfaced in acute neurological disorders, including traumatic brain injury, spinal cord injury, spontaneous intracerebral hemorrhage, and ischemic stroke. An in-depth study of this area will help deepen our understanding of the mechanisms underlying the development of various acute neurological disorders and ultimately improve therapeutic options.
    Keywords:  TRAK; acute neurological disorders; dynein; kinesin; miro; myosin
  15. Child Neurol Open. 2023 Jan-Dec;10:10 2329048X231210421
      ISCA2 loss of function leads to leukodystrophy and developmental regression (multiple mitochondrial dysfunctions syndrome 4 (MMDS4)). We present a first Korean case of MMDS4 presenting with rapid developmental regression and leukodystrophy after febrile episode, mimicking post-infectious encephalitis. The patient had displayed normal development until 12 months of age. At 13 months of age, one month after experiencing a post-vaccination fever, she quickly progressed to being unable to sit unassisted nor speak any words. Analysis of the cerebrospinal fluid (CSF) revealed lympho-dominant pleocytosis. Amino acid analysis of both the serum and CSF demonstrated elevated glycine exclusively in the CSF. Diffuse leukodystrophy was noted in the brain magnetic resonance image. Whole exome sequencing revealed compound heterozygous ISCA2 variants of c.166T>G, p.C56G and c.422A>C, p.Q141P. No evidence of mitochondrial disease other than bilateral optic atrophy was noted. In cases of early onset rapid developmental regression with leukodystrophy, MMDS4 should be considered.
    Keywords:  ISCA2; developmental regression; glycine; leukodystrophy; multiple mitochondrial dysfunctions syndrome 4
  16. Expert Opin Drug Deliv. 2023 Nov 03.
      INTRODUCTION: Ischemic stroke-induced mitochondrial dysfunction in brain endothelial cells (BECs) leads to breakdown of the blood-brain barrier (BBB) causing long-term neurological dysfunction. Restoration of mitochondrial function in injured BECs is a promising therapeutic strategy to alleviate stroke-induced damage. Mounting evidence demonstrate that selected subsets of cell-derived extracellular vehicles (EVs), such as exosomes (EXOs) and microvesicles (MVs), contain functional mitochondrial components. Therefore, development of BEC-derived mitochondria-containing EVs for delivery to the BBB will (1) alleviate mitochondrial dysfunction and limit long-term neurological dysfunction in ischemic stroke and (2) provide an alternative therapeutic option for treating numerous other diseases associated with mitochondrial dysfunction.AREA COVERED: This review will discuss (1) how EV subsets package different types of mitochondrial components during their biogenesis, (2) mechanisms of EV internalization and functional mitochondrial responses in the recipient cells, and (3) EV biodistribution and pharmacokinetics - key factors involved in the development of mitochondria-containing EVs as a novel BBB-targeted stroke therapy.
    EXPERT OPINION: Mitochondria-containing MVs have demonstrated therapeutic benefits in ischemic stroke and other pathologies associated with mitochondrial dysfunction. Delivery of MV mitochondria to the BBB is expected to protect the BBB integrity and neurovascular unit post-stroke. MV mitochondria quality control, characterization, mechanistic understanding of its effects in vivo, safety and efficacy in different preclinical models, large-scale production, and establishment of regulatory guidelines are foreseeable milestones to harness the clinical potential of MV mitochondria delivery.
    Keywords:  BBB; Exosomes; Microvesicles; Mitochondria; extracellular vesicles; stroke
  17. Nat Commun. 2023 Nov 01. 14(1): 6770
      Type I interferon (IFN) signalling is tightly controlled. Upon recognition of DNA by cyclic GMP-AMP synthase (cGAS), stimulator of interferon genes (STING) translocates along the endoplasmic reticulum (ER)-Golgi axis to induce IFN signalling. Termination is achieved through autophagic degradation or recycling of STING by retrograde Golgi-to-ER transport. Here, we identify the GTPase ADP-ribosylation factor 1 (ARF1) as a crucial negative regulator of cGAS-STING signalling. Heterozygous ARF1 missense mutations cause a previously unrecognized type I interferonopathy associated with enhanced IFN-stimulated gene expression. Disease-associated, GTPase-defective ARF1 increases cGAS-STING dependent type I IFN signalling in cell lines and primary patient cells. Mechanistically, mutated ARF1 perturbs mitochondrial morphology, causing cGAS activation by aberrant mitochondrial DNA release, and leads to accumulation of active STING at the Golgi/ERGIC due to defective retrograde transport. Our data show an unexpected dual role of ARF1 in maintaining cGAS-STING homeostasis, through promotion of mitochondrial integrity and STING recycling.
  18. Nature. 2023 Oct 28.
    Keywords:  CRISPR-Cas9 genome editing; Cardiovascular biology; Gene therapy; Medical research
  19. Kidney Dis (Basel). 2023 Aug;9(4): 254-264
      Background: Podocytes are essential components of the glomerular filtration barrier and essential for the proper filtration function of the glomerulus. Podocyte injury under various stress conditions is the primary pathogenesis and key determinant of focal segmental glomerulosclerosis (FSGS) with prominent clinical manifestations of proteinuria or nephrotic syndrome.Summary: Under physiological conditions, a highly coordinated mitochondrial quality control system, including antioxidant defenses, mitochondrial dynamics (fusion, fission, and mitophagy), and mitochondrial biogenesis, guarantees the sophisticated structure and various functions of podocytes. However, under FSGS pathological conditions, mitochondria encounter oxidative stress, dynamics disturbances, and defective mitochondrial biogenesis. Moreover, mutations in mitochondrial DNA and mitochondria-related genes are also strongly associated with FSGS. Based on these pieces of evidence, bioactive agents that function to relieve mitochondrial oxidative stress and promote mitochondrial biogenesis have been proven effective in preclinical FSGS models. Targeting the mitochondrial network is expected to provide new therapeutic strategies for the treatment of FSGS and delay its progression to end-stage renal disease.
    Key Messages: Mitochondrial dysfunction plays a key role in podocyte injury and FSGS progression. This review summarized recent advances in the study of mitochondrial homeostatic imbalance and dysfunction in FSGS and discussed the potential of mitochondria-targeted therapeutics in improving FSGS and retarding its progression to end-stage renal disease.
    Keywords:  Focal segmental glomerulosclerosis; Mitochondria; Podocyte
  20. Autophagy. 2023 Nov 01.
      Macroautophagy/autophagy is the intracellular degradation process of cytoplasmic content and damaged organelles. Autophagy is strongly associated with the progression of Alzheimer disease (AD). Microglia are brain-resident macrophages, and recent studies indicate that autophagy in microglia protects neurons from neurodegeneration. Postnatal neurogenesis, the generation of new neurons from adult neural stem cells (NSCs), is impaired in AD patients as well as in AD animal models. However, the extent to which microglial autophagy influences adult NSCs and neurogenesis in AD animal models has not been studied. Here, we showed that conditional knock out (cKO) of Atg5 (autophagy related 5) in microglia inhibited postnatal neurogenesis in the dentate gyrus (DG) of the hippocampus, but not in the subventricular zone (SVZ) of a 5×FAD mouse model. Interestingly, the protection of neurogenesis by Atg5 in microglia was only observed in female AD mice. To confirm the roles of autophagy in microglia for postnatal hippocampal neurogenesis, we generated additional cKO mice to delete autophagy essential genes Rb1cc1 or Atg14 in microglia. However, these rb1cc1 cKO and atg14 cKO mice did not exhibit neurogenesis defects in the context of a female AD mouse model. Last, we used the CSF1R antagonist to deplete ATG5-deficient microglia and this intervention restored neurogenesis in the hippocampus of 5×FAD mice. These results indicate that microglial ATG5 is essential to maintain postnatal hippocampal neurogenesis in a mouse model of AD. Our findings further support the notion that ATG5 in microglia supports NSC health and may prevent neurodegeneration.
    Keywords:  Alzheimer disease; animal model; autophagy; microglia; neural stem cell; neurogenesis
  21. Cell Rep. 2023 Nov 01. pii: S2211-1247(23)01226-3. [Epub ahead of print]42(11): 113214
      Phosphatidylglycerol (PG) is a mitochondrial phospholipid required for mitochondrial cristae structure and cardiolipin synthesis. PG must be remodeled to its mature form at the endoplasmic reticulum (ER) after mitochondrial biosynthesis to achieve its biological functions. Defective PG remodeling causes MEGDEL (non-alcohol fatty liver disease and 3-methylglutaconic aciduria with deafness, encephalopathy, and Leigh-like) syndrome through poorly defined mechanisms. Here, we identify LPGAT1, an acyltransferase that catalyzes PG remodeling, as a candidate gene for MEGDEL syndrome. We show that PG remodeling by LPGAT1 at the ER is closely coordinated with mitochondrial transport through interaction with the prohibitin/TIMM14 mitochondrial import motor. Accordingly, ablation of LPGAT1 or TIMM14 not only causes aberrant fatty acyl compositions but also ER retention of newly remodeled PG, leading to profound loss in mitochondrial crista structure and respiration. Consequently, genetic deletion of the LPGAT1 in mice leads to cardinal features of MEGDEL syndrome, including 3-methylglutaconic aciduria, deafness, dilated cardiomyopathy, and premature death, which are highly reminiscent of those caused by TIMM14 mutations in humans.
    Keywords:  CP: Cell biology; LPGAT1; MEGDEL syndrome; mitochondrial dysfunction; phosphatidylglycerol; prohibitin/TIM complex
  22. JCI Insight. 2023 Nov 02. pii: e174293. [Epub ahead of print]
      Osteoclasts specialize in bone resorption and are critical for bone remodeling. Previous studies have shown that osteoclasts possess abundant mitochondria and derive most energy through oxidative phosphorylation (OXPHOS). However, the energy substrates fueling OXPHOS in osteoclasts remain to be fully defined. Here, we showed that osteoclast differentiation was coupled with increased oxidation of glucose, glutamine and oleate. Transcriptomic analyses with RNA sequencing revealed marked upregulation of genes participating in OXPHOS and mitochondrial fatty acids oxidation, during osteoclast differentiation. Increased mitochondrial oxidation of long-chain fatty acids was required for osteoclast differentiation in vitro. However, blocking fatty acid oxidation in vivo, by deletion of Cpt1a in osteoclast progenitors, impaired osteoclast formation only in the female mice. The Cpt1a-deficient females were further protected from osteoclast activation by a high fat diet. The males, on the contrary, exhibited normal bone resorption despite Cpt1a deletion, regardless of the dietary fat content. Moreover, concurrent deletion of Mpc1 and Cpt1a, blocking mitochondrial oxidation of both glucose and fatty acids in the osteoclast lineage, failed to impede bone resorption in the males. The study therefore uncovers a female-specific dependence on mitochondrial oxidation of fatty acids and glucose in osteoclasts in vivo.
    Keywords:  Bioenergetics; Bone Biology; Osteoclast/osteoblast biology
  23. Mol Psychiatry. 2023 Nov 01.
      Accumulation of amyloid β-peptide (Aβ) is a driver of Alzheimer's disease (AD). Amyloid precursor protein (App) knock-in mouse models recapitulate AD-associated Aβ pathology, allowing elucidation of downstream effects of Aβ accumulation and their temporal appearance upon disease progression. Here we have investigated the sequential onset of AD-like pathologies in AppNL-F and AppNL-G-F knock-in mice by time-course transcriptome analysis of hippocampus, a region severely affected in AD. Strikingly, energy metabolism emerged as one of the most significantly altered pathways already at an early stage of pathology. Functional experiments in isolated mitochondria from hippocampus of both AppNL-F and AppNL-G-F mice confirmed an upregulation of oxidative phosphorylation driven by the activity of mitochondrial complexes I, IV and V, associated with higher susceptibility to oxidative damage and Ca2+-overload. Upon increasing pathologies, the brain shifts to a state of hypometabolism with reduced abundancy of mitochondria in presynaptic terminals. These late-stage mice also displayed enlarged presynaptic areas associated with abnormal accumulation of synaptic vesicles and autophagosomes, the latter ultimately leading to local autophagy impairment in the synapses. In summary, we report that Aβ-induced pathways in App knock-in mouse models recapitulate key pathologies observed in AD brain, and our data herein adds a comprehensive understanding of the pathologies including dysregulated metabolism and synapses and their timewise appearance to find new therapeutic approaches for AD.
  24. Nature. 2023 Nov;623(7986): 246
    Keywords:  Cell biology; Developmental biology; Policy; Stem cells
  25. Front Pharmacol. 2023 ;14 1243258
      Non-alcoholic steatohepatitis (NASH) is known to progress to cirrhosis and hepatocellular carcinoma in some patients. Although NASH is associated with abnormal mitochondrial function related to lipid metabolism, mechanisms for the development and effective treatments are still unclear. Therefore, new approaches to elucidate the pathophysiology are needed. In the previous study, we generated liver organoids from different stages of NASH model mice that could recapitulate the part of NASH pathology. In the present study, we investigated the relationship between mitochondrial function and NASH disease by comparing NASH liver organoids (NLO) and control liver organoids (CLO). Compared with CLO, mitochondrial and organoid morphology was abnormal in NLO, with increased expression of mitochondrial mitogen protein, DRP1, and mitochondria-derived reactive oxygen species (ROS) production. Treatment of NLO with a DPR1 inhibitor, Mdivi-1 resulted in the improvement of morphology and the decreased expression of fibrosis-related markers, Col1a1 and Acta2. In addition, treatment of NASH model mice with Mdivi-1 showed a decrease in fatty liver. Mdivi-1 treatment also prevented fibrosis and ROS production in the liver. These results indicate that NLO undergoes enhanced metabolism and abnormal mitochondrial morphology compared with CLO. It was also suggested that Mdivi-1 may be useful as a therapeutic agent to ameliorate NASH pathology.
    Keywords:  DRP1; NASH; ROS; fibrosis; liver; mitochondria; organoids
  26. Am J Transplant. 2023 Oct 30. pii: S1600-6135(23)00803-1. [Epub ahead of print]
      In clinical organ transplantation, donor and recipient age may differ substantially. Old donor organs accumulate senescent cells that have the capacity to induce senescence in naïve cells. We hypothesized that the engraftment of old organs may induce senescence in younger recipients, promoting age-related pathologies. When performing isogeneic cardiac transplants between age-mismatched C57BL/6 old donor mice (18-months) and young and middle-aged C57BL/6 recipients (3- or 12-months), we observed augmented frequencies of senescent cells in draining lymph nodes, adipose tissue, livers, and hindlimb muscles 30 days after transplantation. These observations went along with compromised physical performance and impaired spatial learning and memory abilities. Systemic levels of SASP factors including mitochondrial DNA (mt-DNA) were elevated in recipients. Of mechanistic relevance, injections of mt-DNA phenocopied effects of age-mismatched organ transplantation in accelerating aging. Single treatment of old donor animals with senolytics prior to transplantation attenuated mt-DNA release and improved physical capacities in young recipients. Collectively, we show that transplanting older organs induces senescence in transplant recipients, resulting in compromised physical and cognitive capacities. Depleting senescent cells with senolytics, in turn represents a promising approach to improve outcomes of older organs.
  27. STAR Protoc. 2023 Oct 27. pii: S2666-1667(23)00641-X. [Epub ahead of print]4(4): 102674
      Prospective isolation of defined cell types is critical for the functional study of stem cells, especially in primary human tissues. Here, we present a protocol for purifying 10 transcriptomically and functionally distinct neural stem and progenitor cell types from the developing human brain using fluorescence-activated cell sorting. We describe steps for tissue dissociation, staining, and cell sorting as well as downstream functional experiments for measuring clonogenicity, differentiation, and engraftment potential of purified populations. For complete details on the use and execution of this protocol, please refer to Liu et al. (2023).1.
    Keywords:  Cell culture; Cell isolation; Cell-based Assays; Classification Description; Developmental biology; Flow Cytometry; Neuroscience; Stem Cells