bims-mitmed 2025-02-09 papers

bims-mitmed

Biomed News

on Mitochondrial medicine

Issue of 2025–02–09
thirty-two papers selected by
Dario Brunetti, Fondazione IRCCS Istituto Neurologico

Activating AMPK improves pathological phenotypes due to mtDNA depletion.
Mitochondrial heterogeneity: subpopulations with distinct metabolic activities.
Functional Characterization of Parallel Fiber-Purkinje Cell Synapses in Two Friedreich's Ataxia Mouse Models.
iPSC models of mitochondrial diseases.
Protocol for assessing the clogging of the mitochondrial translocase of the outer membrane by precursor proteins in human cells.
Inhibition of cytosolic translation mitigates mitochondrial dysfunction in C. elegans.
Novel intronic variant in NDUFS7 gene results in mitochondrial complex I assembly defect with early basal ganglia and midbrain involvement with progressive neuroimaging findings.
Asymmetric partitioning of persistent paternal mitochondria during cell divisions safeguards embryo development and mitochondrial inheritance.
Gene therapy prevents hepatic mitochondrial dysfunction in murine deoxyguanosine kinase deficiency.
Retrograde mitochondrial signaling governs the identity and maturity of metabolic tissues.
Diurnal variation in skeletal muscle mitochondrial function dictates time-of-day-dependent exercise capacity.
The Lily Foundation: supporting patients, raising awareness and funding research into mitochondrial diseases.
Development and validation of a sensitive sandwich ELISA against human PINK1.
Neurochemical alterations in the cerebellum in Friedreich's Ataxia mouse models.
A new player in the mammalian electron transport chain.
An avoidance segment resolves a lethal nuclear-mitochondrial targeting conflict during ribosome assembly.
Mitophagy is induced in human engineered heart tissue after simulated ischemia and reperfusion.
Prenatal Counseling and Diagnosis of COX20 Gene-Related Mitochondrial Complex IV Deficiency: A Case Report and Literature Review.
Harmine promotes axon regeneration through enhancing glucose metabolism.
Arginine: at the crossroads of nitrogen metabolism.
Omega-3 supplements slow biological ageing.
PPARGC1A regulates transcriptional control of mitochondrial biogenesis in early bovine embryos.
Engineered nose bacteria sneak drugs into the brain.
Molecular signature of primate astrocytes reveals pathways and regulatory changes contributing to human brain evolution.
Creating Optimal Western Blot Conditions for OPA1 Isoforms in Skeletal Muscle Cells and Tissue.
Investigating the Interplay Between the Nrf2/Keap1/HO-1/SIRT-1 Pathway and the p75NTR/PI3K/Akt/MAPK Cascade in Neurological Disorders: Mechanistic Insights and Therapeutic Innovations.
Focused ultrasound widely broadens AAV-delivered Cas9 distribution and activity.
A new 'mini-CRISPR' flexes its editing power in monkey muscles.
Imaging and Quantifying Mitochondrial Morphology in C. elegans During Aging.
An atlas of cells in the human brain's control hub.
Mitochondrial transplantation as a novel therapeutic approach in idiopathic inflammatory myopathy.
Metabolic Messengers: small extracellular vesicles.

FEBS J. 2025 Feb 07.

Activating AMPK improves pathological phenotypes due to mtDNA depletion.

Gustavo Carvalho, Tran V H Nguyen, Bruno Repolês, Josefin M E Forslund, W M Ruchitha Rukmal Wijethunga, Farahnaz Ranjbarian, Isabela C Mendes, Choco Michael Gorospe, Namrata Chaudhari, Micol Falabella, Mara Doimo, Sjoerd Wanrooij, Robert D S Pitceathly, Anders Hofer, Paulina H Wanrooij.

  AMP-activated protein kinase (AMPK) is a master regulator of cellular energy homeostasis that also plays a role in preserving mitochondrial function and integrity. Upon a disturbance in the cellular energy state that increases AMP levels, AMPK activity promotes a switch from anabolic to catabolic metabolism to restore energy homeostasis. However, the level of severity of mitochondrial dysfunction required to trigger AMPK activation is currently unclear, as is whether stimulation of AMPK using specific agonists can improve the cellular phenotype following mitochondrial dysfunction. Using a cellular model of mitochondrial disease characterized by progressive mitochondrial DNA (mtDNA) depletion and deteriorating mitochondrial metabolism, we show that mitochondria-associated AMPK becomes activated early in the course of the advancing mitochondrial dysfunction, before any quantifiable decrease in the ATP/(AMP + ADP) ratio or respiratory chain activity. Moreover, stimulation of AMPK activity using the specific small-molecule agonist A-769662 alleviated the mitochondrial phenotypes caused by the mtDNA depletion and restored normal mitochondrial membrane potential. Notably, the agonist treatment was able to partially restore mtDNA levels in cells with severe mtDNA depletion, while it had no impact on mtDNA levels of control cells. The beneficial impact of the agonist on mitochondrial membrane potential was also observed in cells from patients suffering from mtDNA depletion. These findings improve our understanding of the effects of specific small-molecule activators of AMPK on mitochondrial and cellular function and suggest a potential application for these compounds in disease states involving mtDNA depletion.

Keywords:  AMPK; AMP‐activated protein kinase; mitochondrial DNA depletion; polymerase ɣ

DOI:  https://doi.org/10.1111/febs.70006
Signal Transduct Target Ther. 2025 Feb 07. 10(1): 36

Mitochondrial heterogeneity: subpopulations with distinct metabolic activities.

Fabian den Brave, Swadha Mishra, Thomas Becker.

DOI: https://doi.org/10.1038/s41392-025-02130-0
Cerebellum. 2025 Feb 05. 24(2): 42

Functional Characterization of Parallel Fiber-Purkinje Cell Synapses in Two Friedreich's Ataxia Mouse Models.

Donald J Joseph, Elizabeth Mercado-Ayon, Liam Flatley, Angela N Viaene, Juliette Hordeaux, Eric D Marsh, David R Lynch.

  Friedreich ataxia (FRDA) is an autosomal recessive disorder caused by GAA expansions in the FXN gene, which codes for the protein frataxin (FXN). These mutations reduce FXN expression, leading to mitochondrial dysfunction and multisystemic disease. Accumulating evidence suggests that neuronal dysfunction, rather than neuronal death, may drive the neurological phenotypes of FRDA, but the mechanisms underlying such neurological phenotypes remain unclear. To investigate the neural circuit basis of this dysfunction, we employed field recordings to measure Purkinje cell (PC) function and synaptic properties along with western blotting and immunohistochemistry to determine their density and structure in two established FRDA mouse models, the shRNA-frataxin (FRDAkd) and the frataxin knock in-knockout (KIKO) mice. Western blotting demonstrated subtle changes in mitochondrial proteins and only a modest reduction in the density of calbindin positive cells PCs in the cerebellar cortex of the FRDAkd mice, with no change in the density of PCs in the KIKO mice. Though PC density differed slightly in the two models, field recordings of parallel fiber-PC synapses in the molecular layer demonstrated concordant hypo-excitability of basal synaptic transmission and impairments of long-term plasticity using induction protocols associated with both potentiation and depression of synaptic strength. These results indicate that synaptic instability might be a common feature in FRDA mouse models.

Keywords:  And Mitochondria; Cerebellum; Frataxin; Friedreich’s ataxia; Long-term plasticity; Synaptic transmission

DOI:  https://doi.org/10.1007/s12311-025-01796-0
Neurobiol Dis. 2025 Jan 30. pii: S0969-9961(25)00038-5. [Epub ahead of print] 106822

iPSC models of mitochondrial diseases.

Sonja Heiduschka, Alessandro Prigione.

  Mitochondrial diseases are historically difficult to study. They cause multi-systemic defects with prevalent impairment of hard-to-access tissues such as the brain and the heart. Furthermore, they suffer from a paucity of conventional model systems, especially because of the challenges associated with mitochondrial DNA (mtDNA) engineering. Consequently, most mitochondrial diseases are currently untreatable. Human induced pluripotent stem cells (iPSCs) represent a promising approach for developing human model systems and assessing therapeutic avenues in a patient- and tissue-specific context. iPSCs are being increasingly used to investigate mitochondrial diseases, either for dissecting mutation-specific defects within two-dimensional (2D) or three-dimensional (3D) progenies or for unveiling the impact of potential treatment options. Here, we review how iPSC-derived 2D cells and 3D organoid models have been applied to the study of mitochondrial diseases caused by either nuclear or mtDNA defects. We anticipate that the field of iPSC-driven modeling of mitochondrial diseases will continue to grow, likely leading to the development of innovative platforms for treatment discovery and toxicity that could benefit the patient community suffering from these debilitating disorders with highly unmet medical needs.

Keywords:  Brain organoids; Disease modeling; Drug discovery; Mitochondrial diseases; Pluripotent stem cells

DOI:  https://doi.org/10.1016/j.nbd.2025.106822
STAR Protoc. 2025 Jan 31. pii: S2666-1667(25)00023-1. [Epub ahead of print]6(1): 103617

Protocol for assessing the clogging of the mitochondrial translocase of the outer membrane by precursor proteins in human cells.

John Kim, Hilla Weidberg.

  Protein import into the mitochondria is required for organellar function. Inefficient import can result in the stalling of mitochondrial precursors inside the translocase of the outer membrane (TOM) and blockage of the mitochondrial entry gate. Here, we present a protocol to assess the clogging of TOM by mitochondrial precursors in human cell lines. We describe how the localization of mitochondrial precursors can be determined by cellular fractionation. We then show how co-immunoprecipitation can be used to test the stalling of precursors inside TOM. For complete details on the use and execution of this protocol, please refer to Kim et al.1.

Keywords:  cell biology; cell culture; cell separation/fractionation; molecular biology; protein biochemistry; protein expression and purification

DOI:  https://doi.org/10.1016/j.xpro.2025.103617
bioRxiv. 2025 Jan 23. pii: 2025.01.22.634344. [Epub ahead of print]

Inhibition of cytosolic translation mitigates mitochondrial dysfunction in C. elegans.

Avijit Mallick, Yunguang Du, Theresa Ramalho, Rui Li, Levi Ali, Sookyung Kim, Lihua Julie Zhu, Cole M Haynes.

The mitochondrial unfolded protein response (UPR mt ) is regulated by the bZIP protein ATFS-1 which promotes mitochondrial protein homeostasis (proteostasis) and mitochondrial biogenesis in Caenorhabditis elegans . Upon mitochondrial perturbation, the ATFS-1-dependent transcriptional program promotes gene expression, leading to mitochondrial recovery. Conversely, atfs-1 -deletion worms harbor dysfunctional mitochondria, are developmentally impaired, and short-lived. However, atfs-1 -deletion worms develop to adults suggesting the presence of other signaling pathways that promote mitochondrial function and biogenesis in the absence of atfs-1 . We hypothesized that additional transcription factors regulate, or promote, mitochondrial function in the absence of atfs-1 . Here, we screened for transcription factors that could reduce the decline in mitochondrial function in the atfs-1 mutants when inhibited. Here, we demonstrate that inhibition of the nuclear hormone receptor NHR-180 re-establishes a functional mitochondrial network in atfs-1(null) worms, increases mtDNA content, and improves the developmental rate of wildtype worms. NHR-180 increases transcription of genes required for cytosolic protein synthesis in response to mitochondrial perturbation. Inhibition of the S6 kinase homolog, rsks-1 , in atfs-1(null) worms leads to a recovery of the mitochondrial network and mtDNA content consistent with nhr-180 regulating expression of protein synthesis components. Consistent with the observations in C. elegans , S6 kinase inhibition also increased mitochondrial biogenesis in mammalian atf5 -knockout cells that harbor severely impaired mitochondria. Intriguingly, nhr-180 or S6 kinase inhibition also rescues mitochondrial dysfunction caused by mutations in multiple genes required for oxidative phosphorylation. Combined, these studies suggest that increased protein synthesis contributes to the mitochondrial dysfunction caused by perturbations in OXPHOS gene expression and suggest a relatively straightforward approach to reducing the impact of mitochondrial dysfunction.

DOI: https://doi.org/10.1101/2025.01.22.634344
Mitochondrion. 2025 Jan 31. pii: S1567-7249(25)00004-2. [Epub ahead of print] 102007

Novel intronic variant in NDUFS7 gene results in mitochondrial complex I assembly defect with early basal ganglia and midbrain involvement with progressive neuroimaging findings.

Jaakko Oikarainen, Reetta Hinttala, Naemeh Nayebzadeh, Salla M Kangas, Katariina Mankinen, Elisa Rahikkala, Hannaleena Kokkonen, Päivi Vieira, Maria Suo-Palosaari, Johanna Uusimaa.

  Leigh syndrome is the most common phenotype of mitochondrial disorders in children. This study demonstrates clinical, neuroradiological, and molecular genetic findings in siblings with Leigh syndrome and isolated complex I assembly defect associated with intronic c.16 + 5G > A variant in the NDUFS7 gene. Whole exome sequencing was carried out to identify the causative variant. The gene and protein expression of NDUFS7 were studied using patient-derived fibroblasts. Assembly of mitochondrial respiratory chain enzymes was analyzed using Blue Native PAGE. This study shows that the NDUFS7 c.16 + 5G > A variant (rs375282422) has a causative role in Leigh syndrome. Evolution of neuroimaging findings related to this gene variant are demonstrated.

Keywords:  Intronic variant; Leigh syndrome; Mitochondrial; NDUFS7; Neuroimaging; Rare variant

DOI:  https://doi.org/10.1016/j.mito.2025.102007
Dev Cell. 2025 Jan 30. pii: S1534-5807(25)00033-4. [Epub ahead of print]

Asymmetric partitioning of persistent paternal mitochondria during cell divisions safeguards embryo development and mitochondrial inheritance.

Songyun Wang, Ding Xue.

  Most eukaryotes inherit only maternal mitochondria. The reasons for paternal mitochondrial elimination and the impacts of persistent paternal mitochondria on animals remain elusive. We show that undegraded paternal mitochondria in autophagy-deficient C. elegans embryos are gradually excluded from germ blastomeres through asymmetric partitioning during cell divisions. The embryonic cortical flow drives anterior-directed movements of paternal mitochondria and contributes to their asymmetric apportioning between two daughter blastomeres. By contrast, autophagosome-enclosed paternal mitochondria cluster around and segregate with centrosomes during mitosis and are rapidly degraded through lysosomes concentrated near centrosomes. Failure to exclude persistent paternal mitochondria from the germ blastomere at first cleavage causes their enrichment in the descendant endomesodermal (EMS) blastomere, leading to elevated reactive oxygen species levels, elongated EMS lineage durations, and increased embryonic lethality, which antioxidant treatments can suppress. Thus, regulated paternal mitochondrial distribution away from germ blastomeres is a fail-safe mechanism, protecting embryo development and maternal mitochondrial inheritance.

Keywords:  C. elegans; PME; ROS; asymmetric partitioning of mitochondria; autophagy; cortical flow; embryo development; germline blastomere; mitochondrial inheritance; paternal mitochondrial elimination; reactive oxygen species

DOI:  https://doi.org/10.1016/j.devcel.2025.01.013
Mol Ther Methods Clin Dev. 2025 Mar 13. 33(1): 101397

Gene therapy prevents hepatic mitochondrial dysfunction in murine deoxyguanosine kinase deficiency.

Nandaki Keshavan, Miriam Greenwood, Helen Prunty, Juan Antinao Diaz, Riccardo Privolizzi, John Counsell, Anna Karlsson, Neil Sebire, Simon Waddington, Rajvinder Karda, Shamima Rahman.

  Primary mitochondrial disorders are a cause of neonatal liver failure. Biallelic pathogenic variants of the gene encoding the mitochondrial localizing enzyme deoxyguanosine kinase (DGUOK) cause hepatocerebral mitochondrial DNA depletion syndrome, leading to acute neonatal liver failure and early mortality. There are currently no effective disease-modifying therapies. In this study, we developed an adeno-associated virus 9 (AAV9) gene therapy approach to treat a mouse model of DGUOK deficiency that recapitulates human disease. We delivered AAV9-hDGUOK intravenously to newborn Dguok knock-out mice and showed that liver dysfunction was prevented in a dose-dependent manner. Unexpectedly for neonatal delivery, durable and long-lasting liver transduction and RNA expression were observed. Liver mitochondrial DNA depletion, deficiencies of oxidative phosphorylation complexes I, III, and IV and liver transaminitis and survival were ameliorated in a dose-dependent manner.

Keywords:  AAV9; DGUOK deficiency; deoxyguanosine kinase deficiency; gene therapy; mitochondrial DNA depletion syndrome; primary mitochondrial disease

DOI:  https://doi.org/10.1016/j.omtm.2024.101397
Science. 2025 Feb 06. eadf2034

Retrograde mitochondrial signaling governs the identity and maturity of metabolic tissues.

Emily M Walker, Gemma L Pearson, Nathan Lawlor, Ava M Stendahl, Anne Lietzke, Vaibhav Sidarala, Jie Zhu, Tracy Stromer, Emma C Reck, Jin Li, Elena Levi-D'Ancona, Mabelle B Pasmooij, Dre L Hubers, Aaron Renberg, Kawthar Mohamed, Vishal S Parekh, Irina X Zhang, Benjamin Thompson, Deqiang Zhang, Sarah A Ware, Leena Haataja, Nathan Qi, Stephen C J Parker, Peter Arvan, Lei Yin, Brett A Kaufman, Leslie S Satin, Lori Sussel, Michael L Stitzel, Scott A Soleimanpour.

Mitochondrial damage is a hallmark of metabolic diseases, including diabetes, yet the consequences of compromised mitochondria in metabolic tissues are often unclear. Here, we report that dysfunctional mitochondrial quality control engages a retrograde (mitonuclear) signaling program that impairs cellular identity and maturity in β-cells, hepatocytes, and brown adipocytes. Targeted deficiency throughout the mitochondrial quality control pathway, including genome integrity, dynamics, or turnover, impaired the oxidative phosphorylation machinery, activating the mitochondrial integrated stress response, eliciting chromatin remodeling, and promoting cellular immaturity rather than apoptosis to yield metabolic dysfunction. Indeed, pharmacologic blockade of the integrated stress response in vivo restored β-cell identity following loss of mitochondrial quality control. Targeting mitochondrial retrograde signaling may therefore be promising in the treatment or prevention of metabolic disorders.

DOI: https://doi.org/10.1126/science.adf2034
FASEB J. 2025 Feb 15. 39(3): e70365

Diurnal variation in skeletal muscle mitochondrial function dictates time-of-day-dependent exercise capacity.

Subhash Khatri, Souparno Das, Anshit Singh, Shabbir Ahmad, Mohit Kashiv, Sunil Laxman, Ullas Kolthur-Seetharam.

  Exercise impinges on almost all physiological processes at an organismal level and is a potent intervention to treat various diseases. Exercise performance is well established to display diurnal rhythm, peaking during the late active phase. However, the underlying molecular/metabolic factors and mitochondrial energetics that possibly dictate time-of-day exercise capacity remain unknown. Here, we have unraveled the importance of diurnal variation in mitochondrial functions as a determinant of skeletal muscle exercise performance. Our results show that exercise-induced muscle metabolome and mitochondrial energetics are distinct at ZT3 and ZT15. Importantly, we have elucidated key diurnal differences in mitochondrial functions that are well correlated with disparate time-of-day-dependent exercise capacity. Providing causal mechanistic evidence, we illustrate that loss of Sirtuin4 (SIRT4), a well-known mitochondrial regulator, abrogates mitochondrial diurnal variation and consequently abolishes time-of-day-dependent muscle output. Therefore, our findings unequivocally demonstrate the pivotal role of baseline skeletal muscle mitochondrial functions in dictating diurnal exercise capacity.

Keywords:  Sirtuin4 (SIRT4); chronobiology; circadian exercise physiology; exercise metabolism; mitochondrial metabolism; skeletal muscle energetics; time‐of‐day exercise capacity

DOI:  https://doi.org/10.1096/fj.202402930R
FEBS Lett. 2025 Feb 06.

The Lily Foundation: supporting patients, raising awareness and funding research into mitochondrial diseases.

Liz Curtis, Maria E O'Hanlon, Katie Waller, Duncan E Wright.

Primary mitochondrial diseases ('mito') are a group of genetically and phenotypically diverse disorders caused by defects in mitochondrial structure or function. Although they are individually rare, they collectively have an incidence of around 1 : 4300. Mitochondrial diseases can arise from mutations in either mitochondrial or nuclear genes, complicating genetic diagnosis. The Lily Foundation was founded by Liz Curtis in the UK in 2007 in order to raise awareness of mitochondrial diseases and to fund research into diagnosis and treatment. In this first of a new series on patient advocacy, FEBS Letters interviews Founder and CEO Liz Curtis MBE, Head of Patient Programmes Katie Waller and Research Manager Dr. Maria O'Hanlon on the aims, achievements and activities of the Lily Foundation.

DOI: https://doi.org/10.1002/1873-3468.15107
Autophagy. 2025 Feb 06. 1-16

Development and validation of a sensitive sandwich ELISA against human PINK1.

Zahra Baninameh, Jens O Watzlawik, Bernardo A Bustillos, Gabriella Fiorino, Tingxiang Yan, Szymon L Lewicki, Haonan Zhang, Dennis W Dickson, Joanna Siuda, Zbigniew K Wszolek, Wolfdieter Springer, Fabienne C Fiesel.

  The ubiquitin kinase and ligase PINK1 and PRKN together label damaged mitochondria for their elimination in lysosomes by selective autophagy (mitophagy). This cytoprotective quality control pathway is genetically linked to familial Parkinson disease but is also altered during aging and in other neurodegenerative disorders. However, the molecular mechanisms of these mitophagy changes remain uncertain. In healthy mitochondria, PINK1 protein is continuously imported, cleaved, and degraded, but swiftly accumulates on damaged mitochondria, where it triggers the activation of the mitophagy pathway by phosphorylating its substrates ubiquitin and PRKN. Levels of PINK1 protein can therefore be used as a proxy for mitochondrial damage and mitophagy initiation. However, validated methodologies to sensitively detect and quantify PINK1 protein are currently not available. Here, we describe the development and thorough validation of a novel immunoassay to measure human PINK1 on the Meso Scale Discovery platform. The final assay showed excellent linearity, parallelism, and sensitivity. Even in the absence of mitochondrial stress (i.e. at basal conditions), when PINK1 protein is usually not detectable by immunoblotting, significant differences were obtained when comparing samples from patient fibroblasts or differentiated neurons with and without PINK1 expression. Of note, PINK1 protein levels were found increased in human postmortem brain with normal aging, but not in brains with Alzheimer disease, suggesting that indeed different molecular mechanisms are at play. In summary, we have developed a novel sensitive PINK1 immunoassay that will complement other efforts to decipher the roles and biomarker potential of the PINK1-PRKN mitophagy pathway in the physiological and pathological context. Abbreviations: AD: Alzheimer disease; CCCP: carbonyl cyanide 3-chlorophenylhydrazone; ECL: electrochemiluminescence; ELISA: enzyme-linked immunosorbent assay; iPSC: induced pluripotent stem cell; KO: knockout; LLOQ: lower limit of quantification; MSD: Meso Scale Discovery; PD: Parkinson disease; p-S65-Ub: serine-65 phosphorylated ubiquitin; Ub: ubiquitin; ULOQ: upper limit of quantification; WT: wild-type.

Keywords:  Autophagy; P-S65-Ub; PINK1; Parkin; mitophagy; ubiquitin

DOI:  https://doi.org/10.1080/15548627.2025.2457915
Exp Neurol. 2025 Feb 02. pii: S0014-4886(25)00040-8. [Epub ahead of print] 115176

Neurochemical alterations in the cerebellum in Friedreich's Ataxia mouse models.

Elizabeth Mercado Ayón, Ellarie Talgo, Liam Flatley, Jennifer Coulman, David R Lynch.

  Friedreich ataxia (FRDA) is an autosomal recessive neurodegenerative disorder caused by frataxin deficiency. Neurological deficits remain the ubiquitous feature of FRDA and include progressive ataxia and dysarthria, both of which are controlled to a large degree by the cerebellum. The precise impact of frataxin deficiency on the cerebellum including Purkinje cells remains unclear. In the present work, we examined the biochemical and structural properties of the cerebellum and Purkinje cells in the doxycycline-inducible (FRDAkd) and the Knock-in/Knockout (KIKO) mouse models of FRDA. Acute systemic knockdown of frataxin in FRDAkd mice and chronic frataxin deficiency in KIKO leads to a significant decrease in levels of AMPA receptors, particularly GluR2, and an increase in glial glutamate transporters . Significant astroglial accumulation occurred in KIKO cerebellum but not in FRDAkd mice. Purkinje cell dendritic arbors in the molecular layer did not change compared to wildtype in either model. The Purkinje cell postsynaptic receptor NMDAR1 significantly decreased only in the FRDAkd cerebellum while other NMDA receptor subunits, largely found in non-Purkinje cells, did not change. Overall, we observed dysregulated levels of glutamate receptors and transporters in the KIKO and FRDAkd mice models of Friedreich ataxia, suggesting the importance of frataxin in maintaining Purkinje cells and cerebellar integrity along with synaptic properties. These results point to conserved but not identical synaptic features between the models that may represent markers or conceivably targets in human FRDA.

Keywords:  Astrocytosis; Cerebellum; Friedreich ataxia; GluR2; Glutamate receptors

DOI:  https://doi.org/10.1016/j.expneurol.2025.115176
Cell Metab. 2025 Feb 04. pii: S1550-4131(24)00494-7. [Epub ahead of print]37(2): 310-312

A new player in the mammalian electron transport chain.

Judy Hirst.

In an evolutionary twist to mammalian bioenergetics, Spinelli and coworkers reveal the presence of rhodoquinones in mammalian mitochondria, expanding the established premise that the mammalian respiratory chain relies uniquely on ubiquinones for catalysis.

DOI: https://doi.org/10.1016/j.cmet.2024.12.012
Nat Cell Biol. 2025 Jan 31.

An avoidance segment resolves a lethal nuclear-mitochondrial targeting conflict during ribosome assembly.

Michaela Oborská-Oplová, Alexander Gregor Geiger, Erich Michel, Purnima Klingauf-Nerurkar, Sven Dennerlein, Yury S Bykov, Simona Amodeo, André Schneider, Maya Schuldiner, Peter Rehling, Vikram Govind Panse.

The correct sorting of nascent ribosomal proteins from the cytoplasm to the nucleus or to mitochondria for ribosome production poses a logistical challenge for cellular targeting pathways. Here we report the discovery of a conserved mitochondrial avoidance segment (MAS) within the cytosolic ribosomal protein uS5 that resolves an evolutionary lethal conflict between the nuclear and mitochondrial targeting machinery. MAS removal mistargets uS5 to the mitochondrial matrix and disrupts the assembly of the cytosolic ribosome. The resulting lethality can be rescued by impairing mitochondrial import. We show that MAS triages nuclear targeting by disabling a cryptic mitochondrial targeting activity within uS5 and thereby prevents fatal capture by mitochondria. Our findings identify MAS as an essential acquisition by the primordial eukaryote that reinforced organelle targeting fidelity while developing an endosymbiotic relationship with its mitochondrial progenitor.

DOI: https://doi.org/10.1038/s41556-024-01588-4
J Cell Sci. 2025 Feb 06. pii: jcs.263408. [Epub ahead of print]

Mitophagy is induced in human engineered heart tissue after simulated ischemia and reperfusion.

Mireia Nàger, Kenneth B Larsen, Zambarlal Bhujabal, Trine B Kalstad, Judith Rössinger, Truls Myrmel, Florian Weinberger, Asa B Birgisdottir.

  The paradoxical exacerbation of cellular injury and death during reperfusion remains a problem in treatment of myocardial infarction. Mitochondrial dysfunction plays a key role in the pathogenesis of myocardial ischemia and reperfusion injury. Dysfunctional mitochondria can be removed by mitophagy, culminating in their degradation within acidic lysosomes. Mitophagy is pivotal in maintaining cardiac homeostasis and emerges as a potential therapeutic target. Here we employ beating human engineered heart tissue (EHT) to assess mitochondrial dysfunction and mitophagy during ischemia and reperfusion simulation. Our data indicate adverse ultrastructural changes in mitochondrial morphology and impairment of mitochondrial respiration. Furthermore, our pH-sensitive mitophagy reporter EHTs, generated by CRISPR/Cas9 endogenous knock-in strategy, reveal induced mitophagy flux in EHTs after ischemia and reperfusion simulation. The induced flux requires the activity of the protein kinase ULK1, a member of the core-autophagy machinery. Our results demonstrate the applicability of the reporter EHTs for mitophagy assessment in a clinically relevant setting. Deciphering mitophagy in the human heart will facilitate development of novel therapeutic strategies.

Keywords:  Engineered heart tissue; HiPSC; Ischemia-reperfusion; Mitochondria; Mitophagy

DOI:  https://doi.org/10.1242/jcs.263408
Int J Womens Health. 2025 ;17 179-183

Prenatal Counseling and Diagnosis of COX20 Gene-Related Mitochondrial Complex IV Deficiency: A Case Report and Literature Review.

Junyou Su, Lingdong Zeng, Hongfei Chen, Junru Tong, Yan Chen, Lingling Huang, Li Deng, Yan Huang.

   Background: COX20-related mitochondrial complex IV deficiency is a rare autosomal recessive metabolic disorder that arises from biallelic loss-of-function mutations. Given the lack of specific treatments, affected children are at a heightened risk of disability. Consequently, prenatal counseling and prenatal diagnosis should be conducted to reduce the birth rate of children with such mitochondrial diseases. We report a case of COX20 gene associated mitochondrial complex IV deficiency in a child, and describe the prenatal counseling and prenatal diagnosis of the mother in subsequent pregnancies to provide reference for prenatal counseling and prenatal diagnosis of this disease.
Case Presentation: In this study, we presented a case of a pediatric patient who displayed symptoms such as gait instability, ataxia, cognitive impairment, dysarthria, muscle weakness, and absent reflexes. Through the application of whole-exome sequencing (WES), compound heterozygous COX20 mutations (c.41A>G and c.259C>T) were detected, leading to the confirmation of a diagnosis of mitochondrial complex IV deficiency. A thorough review of the existing literature revealed seven additional cases carrying the same mutations. Moreover, this report delineated the process of prenatal counseling and diagnostic testing that was undertaken for the subsequent pregnancy of the patient's mother.
Conclusion: The presence of ataxia, cognitive impairment, and peripheral neuropathy in children should prompt consideration of COX20-related mitochondrial disease. Utilizing WES is beneficial for identifying COX20 mutations, and offering prenatal counseling and diagnostic testing to mothers of affected children can reduce the birth rate of children with such mitochondrial diseases.

Keywords:  COX20; complex IV deficiency; prenatal counseling; prenatal diagnosis

DOI:  https://doi.org/10.2147/IJWH.S505352
J Biol Chem. 2025 Feb 02. pii: S0021-9258(25)00101-2. [Epub ahead of print] 108254

Harmine promotes axon regeneration through enhancing glucose metabolism.

Ruixuan Liu, Bing Zhou.

  Axon regeneration requires a substantial mitochondrial energy supply. However, injured mature neurons often fail to regenerate due to their inability to meet these elevated energy demands. Our findings indicate that harmine compensates for the energy deficit following axonal injury by enhancing the coupling between glucose metabolism and mitochondrial homeostasis, thereby promoting axon regeneration. Notably, harmine facilitates mitochondrial biogenesis and enhances mitophagy, ensuring efficient mitochondrial turnover and energy supply. Thus, harmine plays a crucial role in enhancing glucose metabolism to maintain mitochondrial function, demonstrating significant potential in treating mature neuronal axon injuries and sciatic nerve injuries.

Keywords:  axon regeneration; energy supply; glucose metabolism; harmine; metabolic coupling; mitochondrial function; neuron

DOI:  https://doi.org/10.1016/j.jbc.2025.108254
EMBO J. 2025 Feb 07.

Arginine: at the crossroads of nitrogen metabolism.

Tak Shun Fung, Keun Woo Ryu, Craig B Thompson.

  L-arginine is the most nitrogen-rich amino acid, acting as a key precursor for the synthesis of nitrogen-containing metabolites and an essential intermediate in the clearance of excess nitrogen. Arginine's side chain possesses a guanidino group which has unique biochemical properties, and plays a primary role in nitrogen excretion (urea), cellular signaling (nitric oxide) and energy buffering (phosphocreatine). The post-translational modification of protein-incorporated arginine by guanidino-group methylation also contributes to epigenetic gene control. Most human cells do not synthesize sufficient arginine to meet demand and are dependent on exogenous arginine. Thus, dietary arginine plays an important role in maintaining health, particularly upon physiologic stress. How cells adapt to changes in extracellular arginine availability is unclear, mostly because nearly all tissue culture media are supplemented with supraphysiologic levels of arginine. Evidence is emerging that arginine-deficiency can influence disease progression. Here, we review new insights into the importance of arginine as a metabolite, emphasizing the central role of mitochondria in arginine synthesis/catabolism and the recent discovery that arginine can act as a signaling molecule regulating gene expression and organelle dynamics.

Keywords:  Arginine Deficiency; Arginine Metabolism; Metabolite Signaling; Mitochondria; Protein Synthesis

DOI:  https://doi.org/10.1038/s44318-025-00379-3
Nature. 2025 Feb 03.

Omega-3 supplements slow biological ageing.

Felicity Nelson.



Keywords:  Ageing; Epigenetics; Molecular biology

DOI:  https://doi.org/10.1038/d41586-025-00355-1
Front Cell Dev Biol. 2024 ;12 1531378

PPARGC1A regulates transcriptional control of mitochondrial biogenesis in early bovine embryos.

Muhammad Idrees, Zaheer Haider, Chalani Dilshani Perera, Safeer Ullah, Seo-Hyeon Lee, Seung Eun Lee, Sung-Sik Kang, Sung Woo Kim, Il-Keun Kong.

  Extensive mitochondrial replication during oogenesis and its role in oocyte maturation and fertilization indicate that the amount of mitochondrial DNA (mtDNA) may play a significant role in early embryonic development. Early embryos express peroxisome proliferator-activated receptor gamma co-activator alpha (PPARGC1A/PGC-1a), a protein essential for mitochondrial biogenesis. This study investigated the role of PGC-1α from a single-cell zygotic stage to day-8 bovine blastocyst and the effect of PGC-1a knockdown (KD) on embryo mitochondria and development. PGC-1α KD via siRNA injection into single-cell zygotes does not substantially affect embryonic cleavage up to the morula stage but considerably reduces blastocyst development (18.42%) and hatching than the control (32.81%). PGC-1α regulates transcription of the gene encoding mitochondrial transcription factor A (TFAM), and immunofluorescence analysis indicated significantly lower TFAM expression in the 16-cell KD embryos and day-8 KD blastocysts. Reduction in NRF1 protein's nuclear localization in bovine blastomeres was also observed in PGC-1α-KD embryos. Furthermore, to understand the effect of PGC-1α-KD on the mitochondrial genome, we found a low mtDNA copy number in PGC-1α-KD day-8 bovine blastocysts. Several genes related to mitochondrial functioning, like ND1, ND3, ND5, ATPase8, COI, COII, and CYTB, were significantly downregulated in PGC-1α-KD embryos. Moreover, high mitochondrial depolarization (ΔΨm) and abnormal lipid depositions were observed in the PGC-1α KD blastocysts. SIRT1 is the upstream regulator of PGC-1α, but SIRT1 activation via Hesperetin does not affect PGC-1α-KD embryonic development considerably. In conclusion, PGC-1α plays a critical role in early embryo mitochondrial functioning, and any perturbation in its expression significantly disrupts early embryonic development.

Keywords:  NRF; PGC-1α; TFAM; bovine blastocyst; mitochondrial DNA

DOI:  https://doi.org/10.3389/fcell.2024.1531378
Nature. 2025 Feb 06.

Engineered nose bacteria sneak drugs into the brain.

Heidi Ledford.



Keywords:  Brain; Medical research; Microbiology; Microbiome

DOI:  https://doi.org/10.1038/d41586-025-00375-x
Cell Stem Cell. 2025 Jan 29. pii: S1934-5909(24)00458-2. [Epub ahead of print]

Molecular signature of primate astrocytes reveals pathways and regulatory changes contributing to human brain evolution.

Katarzyna Ciuba, Aleksandra Piotrowska, Debadeep Chaudhury, Bondita Dehingia, Eryk Duński, Rüdiger Behr, Karolina Soroczyńska, Małgorzata Czystowska-Kuźmicz, Misbah Abbas, Edyta Bulanda, Sylwia Gawlik-Zawiślak, Sylwia Pietrzak, Izabela Figiel, Jakub Włodarczyk, Alexei Verkhratsky, Marcin Niedbała, Wojciech Kaspera, Tomasz Wypych, Bartosz Wilczyński, Aleksandra Pękowska.

  Astrocytes contribute to the development and regulation of the higher-level functions of the brain, the critical targets of evolution. However, how astrocytes evolve in primates is unsettled. Here, we obtain human, chimpanzee, and macaque induced pluripotent stem-cell-derived astrocytes (iAstrocytes). Human iAstrocytes are bigger and more complex than the non-human primate iAstrocytes. We identify new loci contributing to the increased human astrocyte. We show that genes and pathways implicated in long-range intercellular signaling are activated in the human iAstrocytes and partake in controlling iAstrocyte complexity. Genes downregulated in human iAstrocytes frequently relate to neurological disorders and were decreased in adult brain samples. Through regulome analysis and machine learning, we uncover that functional activation of enhancers coincides with a previously unappreciated, pervasive gain of "stripe" transcription factor binding sites. Altogether, we reveal the transcriptomic signature of primate astrocyte evolution and a mechanism driving the acquisition of the regulatory potential of enhancers.

Keywords:  astrocytes; enhancers; evolution; evolution of cell shape; genomics; iPS cell-derived astrocytes; neurological disorders

DOI:  https://doi.org/10.1016/j.stem.2024.12.011
Curr Protoc. 2025 Feb;5(2): e70004

Creating Optimal Western Blot Conditions for OPA1 Isoforms in Skeletal Muscle Cells and Tissue.

Margaret Mungai, Amber Crabtree, Han Le, Johnathan Moore, Desiree Nguyen, Benjamin Rodriguez, Chanel Harris, Dominique C Stephens, Heather K Beasley, Edgar Garza-Lopez, Kit Neikirk, Bryanna Shao, Ashton Oliver, Genesis Wilson, Serif Bacevac, Larry Vang, Zer Vue, Neng Vue, Andrea G Marshall, Kyrin Turner, Elma Zaganjor, Jianqiang Shao, Sandra Murray, Jennifer A Gaddy, Celestine Wanjalla, Jamaine Davis, Steven M Damo, Lori D Banks, Antentor Hinton.

  OPA1 is a dynamin-related GTPase that modulates mitochondrial dynamics and cristae integrity. Humans carry eight different isoforms of OPA1 and mice carry five, all of which are expressed as short- or long-form isoforms. These isoforms contribute to OPA1's ability to control mitochondrial energetics and DNA maintenance. However, western blot isolation of all long and short isoforms of OPA1 can be difficult. To address this issue, we developed an optimized western blot protocol based on improving running time to isolate five different isoforms of OPA1 in mouse cells and tissues. This protocol can be applied to study changes in mitochondrial structure and function. © 2025 The Author(s). Current Protocols published by Wiley Periodicals LLC. Basic Protocol: Western Blot Protocol for Isolating OPA1 Isoforms in Mouse Primary Skeletal Muscle Cells.

Keywords:  isoforms; mitochondria; muscle tissue; optic atrophy‐1 (OPA1); western blot

DOI:  https://doi.org/10.1002/cpz1.70004
Mol Neurobiol. 2025 Feb 07.

Investigating the Interplay Between the Nrf2/Keap1/HO-1/SIRT-1 Pathway and the p75NTR/PI3K/Akt/MAPK Cascade in Neurological Disorders: Mechanistic Insights and Therapeutic Innovations.

Ritam Mukherjee, Ravi Rana, Sidharth Mehan, Zuber Khan, Ghanshyam Das Gupta, Acharan S Narula, Rajaram Samant.

  Neurological illnesses are debilitating diseases that affect brain function and balance. Due to their complicated aetiologies and progressive nature, neurodegenerative and neuropsychiatric illnesses are difficult to treat. These incurable conditions damage brain functions like mobility, cognition, and emotional regulation, but medication, gene therapy, and physical therapy can manage symptoms. Disruptions in cellular signalling pathways, especially those involving oxidative stress response, memory processing, and neurotransmitter modulation, contribute to these illnesses. This review stresses the interplay between key signalling pathways involved in neurological diseases, such as the Nrf2/Keap1/HO-1/SIRT-1 axis and the p75NTR/PI3K/Akt/MAPK cascade. To protect neurons from oxidative damage and death, the Nrf2 transcription factor promotes antioxidant enzyme production. The Keap1 protein releases Nrf2 during oxidative stress for nuclear translocation and gene activation. The review also discusses how neurotrophin signalling through the p75 neurotrophin receptor (p75NTR) determines cell destiny, whether pro-survival or apoptotic. The article highlights emerging treatment approaches targeting these signalling pathways by mapping these connections. Continued research into these molecular pathways may lead to new neurological disease treatments that restore cellular function and neuronal survival. In addition to enhanced delivery technologies, specific modulators and combination therapies should be developed to fine-tune signalling responses. Understanding these crosstalk dynamics is crucial to strengthening neurological illness treatment options and quality of life.

Keywords:  Akt; HO-1; Keap1; MAPKs; Neurodegeneration; Neurological disorders; Neuropsychiatric disorders; Nrf2; P75NTR; PI3K; SIRT-1 axis; Therapeutic strategies

DOI:  https://doi.org/10.1007/s12035-025-04725-8
Gene Ther. 2025 Feb 01.

Focused ultrasound widely broadens AAV-delivered Cas9 distribution and activity.

Emrah Gumusgoz, Sahba Kasiri, Ibrahim Youssef, Mayank Verma, Rajiv Chopra, Daniel Villarreal Acha, Jun Wu, Ummay Marriam, Esther Alao, Xin Chen, Dikran R Guisso, Steven J Gray, Bhavya R Shah, Berge A Minassian.

Because children have little temporal exposure to environment and aging, most pediatric neurological diseases are inherent, i.e. genetic. Since postnatal neurons and astrocytes are mostly non-replicating, gene therapy and genome editing present enormous promise in child neurology. Unlike in other organs, which are highly permissive to adeno-associated viruses (AAV), the mature blood-brain barrier (BBB) greatly limits circulating AAV distribution to the brain. Intrathecal administration improves distribution but to no more than 20% of brain cells. Focused ultrasound (FUS) opens the BBB transiently and safely. In the present work we opened the hippocampal BBB and delivered a Cas9 gene via AAV9 intrathecally. This allowed brain first-pass, and subsequent vascular circulation and re-entry through the opened BBB. The mouse model used was of Lafora disease, a neuroinflammatory disease due to accumulations of misshapen overlong-branched glycogen. Cas9 was targeted to the gene of the glycogen branch-elongating enzyme glycogen synthase. We show that FUS dramatically (2000-fold) improved hippocampal Cas9 distribution and greatly reduced the pathogenic glycogen accumulations and hippocampal inflammation. FUS is in regular clinical use for other indications. Our work shows that it has the potential to vastly broaden gene delivery or editing along with clearance of corresponding pathologic basis of brain disease.

DOI: https://doi.org/10.1038/s41434-025-00517-w
Science. 2025 Feb 07. 387(6734): 570

A new 'mini-CRISPR' flexes its editing power in monkey muscles.

Jennifer Couzin-Frankel.

The downsized DNA-slicing machinery may reach more tissues to take aim at more diseases.

DOI: https://doi.org/10.1126/science.adw4916
J Vis Exp. 2025 Jan 17.

Imaging and Quantifying Mitochondrial Morphology in C. elegans During Aging.

Juri Kim, Maxim Averbukh, Athena Alcala, Rebecca Aviles Barahona, Matthew Vega, Gilberto Garcia, Ryo Higuchi-Sanabria, Naibedya Dutta.

Mitochondria, important cellular organelles found in most eukaryotic cells, are major sites of energy production through aerobic respiration. Beyond this well-known role as the 'cellular powerhouse,' mitochondria are also involved in many other essential cellular processes, including the regulation of cellular metabolism, proliferation, immune signaling, and hormonal signaling. Deterioration in mitochondrial function during aging or under mitochondrial stress is often characterized by distinct changes in mitochondrial morphology and volume. The nematode C. elegans is an ideal model for studying these changes due to its transparent body and short lifespan, which facilitate live microscopy throughout its lifetime. However, even within the C. elegans field, numerous transgenic constructs and methods for mitochondrial imaging are available, each with its own limitations. Here, single-copy, matrix-localized GFP constructs are presented as a robust and reliable method for imaging mitochondrial morphology in C. elegans. This study specifically focuses on experimentally controllable factors to minimize errors and reduce variability between replicates and across studies when performing mitochondrial imaging during the aging process. Additionally, mitoMAPR is recommended as a robust method to quantify changes in mitochondrial morphology across tissue types during aging.

DOI: https://doi.org/10.3791/67610
Nature. 2025 Feb 05.

An atlas of cells in the human brain's control hub.



Keywords:  Brain; Neuroscience; Transcriptomics

DOI:  https://doi.org/10.1038/d41586-025-00314-w
Ann Rheum Dis. 2025 Jan 31. pii: S0003-4967(25)00070-6. [Epub ahead of print]

Mitochondrial transplantation as a novel therapeutic approach in idiopathic inflammatory myopathy.

Jeong Yeon Kim, Young Cheol Kang, Min Jung Kim, Seon Uk Kim, Hae Rim Kang, Jeong Seon Yeo, Yujin Kim, Shin-Hye Yu, Byeongwook Song, Jung Wook Hwang, Yun-Sang Lee, Jung Woo Byun, Dae Hyun Yoo, Hyun Sook Kim, Kyuboem Han, Chun-Hyung Kim, Eun Young Lee.

OBJECTIVES: This study aimed to investigate the efficacy of mitochondrial transplantation as a therapeutic intervention for idiopathic inflammatory myopathy (IIM). This study used a comprehensive approach, incorporating both in vitro and in vivo IIM models, and conducted a first-in-human clinical trial to assess the effectiveness and safety of mitochondria isolated from human umbilical cord mesenchymal stem cells (PN-101).
METHODS: Mitochondria isolated from umbilical cord mesenchymal stem cells were designated as PN-101. The efficacy of PN-101 was assessed using myoblasts derived from patients with IIM and C2C12 mouse perforin/granzyme B-treated myoblasts as an in vitro IIM model. PN-101's effect on IIM was examined using C protein-induced myositis (CIM) mice as an in vivo model. The efficacy and safety of PN-101 were evaluated in a phase 1/2a clinical trial involving 9 adult patients with refractory polymyositis or dermatomyositis.
RESULTS: The myoblasts derived from patients with IIM exhibited defects in mitochondrial function and myogenesis. PN-101 transplantation enhances muscle differentiation and mitochondrial function in IIM myoblasts. PN-101 also enhanced intracellular adenosine triphosphate content, cell viability, and myogenesis in C2C12 perforin/granzyme B-treated myoblasts. In an in vivo model, PN-101 reduced myositis severity by exhibiting anti-inflammatory effects and restoring the CIM-induced metabolic shift. In a phase 1/2a prospective clinical trial involving adult patients with refractory IIM, PN-101 demonstrated no severe adverse drug reactions and showed at least minimal improvement in the International Myositis Assessment and Clinical Studies Group (IMACS)-Total Improvement Scores (TISs) compared with baseline.
CONCLUSIONS: PN-101 transplantation could serve as a novel treatment for IIM by enhancing mitochondrial repair and reducing inflammation in muscle tissues.

DOI: https://doi.org/10.1016/j.ard.2024.11.005
Nat Metab. 2025 Feb 07.

Metabolic Messengers: small extracellular vesicles.

Theresa V Rohm, Karina Cunha E Rocha, Jerrold M Olefsky.

Small extracellular vesicles (sEVs) are signalling molecules and biomarkers of cell status that govern a complex intraorgan and interorgan communication system through their cargo. Initially recognized as a waste disposal mechanism, they have emerged as important metabolic regulators. They transfer biological signals to recipient cells through their cargo content, and microRNAs (miRNAs) often mediate their metabolic effects. This review provides a concise overview of sEVs, specifically in the context of obesity-associated chronic inflammation and related metabolic disorders, describing their role as metabolic messengers, identifying their key sites of action and elucidating their mechanisms. We highlight studies that have shaped our understanding of sEV metabolism, address critical questions for future exploration, discuss the use of miRNAs as disease biomarkers and provide insights into the therapeutic potential of sEVs or specific miRNAs for treating metabolic diseases and related disorders in the future.

DOI: https://doi.org/10.1038/s42255-024-01214-5