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Mitochondrial resilience: a convergent framework for pathogenesis and neuroprotection in Parkinson's disease.

Parkinson's disease (PD) is traditionally described as a dopaminergic neurodegenerative disorder driven by α-synuclein aggregation and selective neuronal loss in the substantia nigra pars compacta. While this characterization captures the core clinical and pathological features, it does not fully explain disease initiation and progression. Converging evidence from human genetics, cellular and structural biology, and systems neuroscience now supports a unified framework in which PD results from the progressive erosion of mitochondrial resilience. Here, mitochondrial resilience denotes the capacity of neuronal mitochondrial networks to withstand stress and recover bioenergetic and cellular homeostasis through coordinated quality control, metabolic adaptation, and organelle communication. Rare, high-impact monogenic mutations in PINK1, PRKN (encoding Parkin), PARK7 (DJ-1), LRRK2, and SNCA, along with common risk variants identified in genome-wide association studies, converge on interconnected pathways that govern mitochondrial quality control, bioenergetics, organelle dynamics, and cellular stress responses. These vulnerabilities are most pronounced in the highly energetic dopaminergic neurons of the substantia nigra, where sustained calcium cycling, high bioenergetic demand, and environmental stressors increase cellular susceptibility. Research has moved beyond early observations of respiratory chain impairment and oxidative stress to reveal context-specific disruptions in PINK1/Parkin-mediated mitophagy, lysosomal trafficking, mitochondrial-derived vesicle dynamics, and neuroimmune signaling. This integrated framework reframes PD as a disorder of impaired cellular maintenance rather than solely a consequence of late-stage degenerative processes. It provides a translational shift from mechanism-based biomarkers to early detection of mitochondrial failure and supports therapeutic strategies aimed at restoring mitochondrial function and resilience, offering a direct route to disease-modifying neuroprotection in PD and potentially other neurodegenerative disorders.

LRRK2↗

AAA proteases of mitochondria: quality control of membrane proteins and regulatory functions during mitochondrial biogenesis.

An ubiquitous and conserved proteolytic system regulates the stability of mitochondrial inner membrane proteins. Two AAA proteases with catalytic sites at opposite membrane surfaces form a membrane-integrated quality control system and exert crucial functions during the biogenesis of mitochondria. Their activity is modulated by another membrane-protein complex that is composed of prohibitins. Peptides generated upon proteolysis in the matrix space are transported across the inner membrane by an ATP-binding cassette transporter. The function of these conserved components is discussed in the present review.

Chloroplasts↗

Nuclear genes and oxidative phosphorylation disorders: a review.

UNLABELLED: Knowledge concerning the approximately 70 human nuclear genes creating the essential building-blocks of the five multi-protein subunit complexes of the oxidative phosphorylation (OXPHOS) system has been expanded greatly in the past few years. However, knowledge concerning the numerous human genes involved in the regulation of transcription, translation, post-translational modification, mitochondrial signalling, import, quality control, folding and assembly of the OXPHOS system is still rather scanty. It may be expected that this scenario, by the application of direct (candidate gene identification by comparison between known genes in lower species and the human expressed sequence tag database) and indirect genetic strategies (the chromosome transfer technique, linkage analysis and positional cloning) will rapidly change. By now, a limited number of structural and non-structural nuclear gene defects have been found. CONCLUSION: This review summarises the state of our current knowledge of nuclear gene mutations in oxidative phosphorylation disorders.

DNA↗

Coupling of mitochondrial translation with the formation of respiratory complexes in yeast mitochondria.

In contrast to most other eukaryotic organisms, yeast can survive without respiration. This ability has been exploited to investigate nuclear genes required for expression of mitochondrial DNA. Availability of complete Saccharomyces cerevisiae genomic sequence has provided additional help in detailed molecular analysis. Seven of the eight major products encoded by mitochondrial DNA are hydrophobic subunits of respiratory complexes in the inner membrane. Localization of the translation process in the same cellular compartment ensures synthesis of mitochondrially encoded proteins near sites of their assembly into multimeric respiratory complexes. Association of mitochondrial ribosomes with the membrane is mediated by mRNA-specific translational activators, that are involved in the recognition of initiation codon. The newly synthesized mitochondrial proteins are transferred to membrane by a specific export system. This review discusses the role of membrane-localized factors responsible for quality control and turnover of mitochondrially synthesized subunits as well as for assembly of respiratory complexes.

Electron Transport↗

Pre- and post-insemination episodes of sexual selection in the fowl, Gallus g. domesticus.

Although much attention has been recently directed to sexual selection arising after insemination from sexual promiscuity, little is known about the mechanisms determining reproductive success after insemination, and the way these mechanisms interact with each other and with selective mechanisms occurring before insemination: mate choice and mate acquisition. Here, we briefly review the findings of an on-going study investigating the mechanisms generating variation in reproductive success at both a pre- and a post-insemination stage in the domestic fowl. Female preference consistently favours socially dominant males before and after insemination. However, although social status mediates the number of sperm that a male inseminates into a female, dominant males may inseminate sperm of lower fertilising quality than their subordinates. We argue that mitochondrial genes may contribute to determine sperm quality, and speculate that the maternal control of mitochondrial genes may prevent sexual selection from operating on males, thus explaining both the lack of a positive correlation between social dominance and sperm quality and the maintenance of variation in male quality in the fowl.

Animals↗

Disruption of mitonuclear coadaptation and compensatory evolution after an extreme dietary shift in carnivorous butterflies.

Mitochondrial function depends on tight coordination between mitochondrial and nuclear genomes, which requires long-term coevolution to maintain mitonuclear coadaptation. While mitonuclear incompatibility is typically studied in the context of hybridization, other evolutionary scenarios that may disrupt coadaptation between the two genomes remain less explored. Here, we propose that extreme ecological niche shifts may disrupt mitonuclear coadaptation, which we test in carnivorous Miletinae butterflies with an extreme dietary transition. By generating high-quality genome assemblies, we found that Miletinae exhibit extensive chromosomal rearrangements. Comparative phylogenomic analyses revealed a striking asymmetric mitonuclear evolutionary response: Miletinae exhibit elevated mitochondrial nucleotide substitution rates compared to phytophagous relatives, whereas nuclear rates remain stable. This shift reverses the typical lepidopteran pattern where nuclear rates exceed mitochondrial rates. Interestingly, this mitochondrial acceleration is driven primarily by relaxed purifying selection rather than positive selection. To sustain mitochondrial function, the nuclear genome of Miletinae underwent pervasive, multilayered compensatory evolution. We detected strong signatures of positive selection and accelerated evolution in nuclear genes directly interacting with mitochondrial components across oxidative phosphorylation (OXPHOS) complexes, the mitochondrial translation, and replication and transcription machinery. Furthermore, this nuclear compensatory response extends to systems governing mitochondrial homeostasis, including protein quality control and RNA degradation and stabilization. Our results support a model in which extreme ecological transitions can disrupt ancestral mitonuclear coadaptation and promote the emergence of a new coadapted state through systemic nuclear compensation. This study broadens the conceptual framework of mitonuclear coevolution and highlights its role in facilitating evolutionary persistence after major ecological shifts.

Animals↗

MAP-1 and IAP-1, two novel AAA proteases with catalytic sites on opposite membrane surfaces in mitochondrial inner membrane of Neurospora crassa.

Eukaryotic AAA proteases form a conserved family of membrane-embedded ATP-dependent proteases but have been analyzed functionally only in the yeast Saccharomyces cerevisiae. Here, we have identified two novel members of this protein family in the filamentous fungus Neurospora crassa, which were termed MAP-1 and IAP-1. Both proteins are localized to the inner membrane of mitochondria. They are part of two similar-sized high molecular mass complexes, but expose their catalytic sites to opposite membrane surfaces, namely, the intermembrane and the matrix space. Disruption of iap-1 by repeat-induced point mutation caused a slow growth phenotype at high temperature and stabilization of a misfolded inner membrane protein against degradation. IAP-1 could partially substitute for functions of its yeast homolog Yme1, demonstrating functional conservation. However, respiratory growth at 37 degrees C was not restored. Our results identify two components of the quality control system of the mitochondrial inner membrane in N. crassa and suggest that AAA proteases with catalytic sites exposed to opposite membrane surfaces are present in mitochondria of all eukaryotic cells.

ATP-Dependent Proteases↗

A call for mtDNA data quality control in forensic science.

There is increasing evidence that many of the mitochondrial DNA (mtDNA) databases published in the fields of forensic science and molecular anthropology are flawed. An a posteriori phylogenetic analysis of the sequences could help to eliminate most of the errors and thus greatly improve data quality. However, previously published caveats and recommendations along these lines were not yet picked up by all researchers. Here we call for stringent quality control of mtDNA data by haplogroup-directed database comparisons. We take some problematic databases of East Asian mtDNAs, published in the Journal of Forensic Sciences and Forensic Science International, as examples to demonstrate the process of pinpointing obvious errors. Our results show that data sets are not only notoriously plagued by base shifts and artificial recombination but also by lab-specific phantom mutations, especially in the second hypervariable region (HVR-II).

DNA Fingerprinting↗

Variable and tissue-specific subunit composition of mitochondrial m-AAA protease complexes linked to hereditary spastic paraplegia.

The m-AAA protease, an ATP-dependent proteolytic complex in the mitochondrial inner membrane, controls protein quality and regulates ribosome assembly, thus exerting essential housekeeping functions within mitochondria. Mutations in the m-AAA protease subunit paraplegin cause axonal degeneration in hereditary spastic paraplegia (HSP), but the basis for the unexpected tissue specificity is not understood. Paraplegin assembles with homologous Afg3l2 subunits into hetero-oligomeric complexes which can substitute for yeast m-AAA proteases, demonstrating functional conservation. The function of a third paralogue, Afg3l1 expressed in mouse, is unknown. Here, we analyze the assembly of paraplegin into m-AAA complexes and monitor consequences of paraplegin deficiency in HSP fibroblasts and in a mouse model for HSP. Our findings reveal variability in the assembly of m-AAA proteases in mitochondria in different tissues. Homo-oligomeric Afg3l1 and Afg3l2 complexes and hetero-oligomeric assemblies of both proteins with paraplegin can be formed. Yeast complementation studies demonstrate the proteolytic activity of these assemblies. Paraplegin deficiency in HSP does not result in the loss of m-AAA protease activity in brain mitochondria. Rather, homo-oligomeric Afg3l2 complexes accumulate, and these complexes can substitute for housekeeping functions of paraplegin-containing m-AAA complexes. We therefore propose that the formation of m-AAA proteases with altered substrate specificities leads to axonal degeneration in HSP.

ATP-Dependent Proteases↗

Diagnosis of mitochondrial disorders: clinical and biochemical approach.

The topic of Workshop W3-1 was clinical and biochemical approaches to the diagnosis of mitochondrial respiratory chain disorders. Four main questions were addressed in an attempt to make some progress towards a consensus diagnostic approach: What are the major limitations in diagnosis of respiratory chain dysfunction? What is the ideal approach to investigating children with a suspected respiratory chain disorder? Can we begin to develop consensus diagnostic criteria? Can we develop a quality assurance (QA) scheme for respiratory chain enzyme assays? The workshop demonstrated strong consensus on recognizing the limitations of current diagnostic approaches, on the ideal diagnostic approach and on the desirability of an enzyme QA scheme. There was also support for the desirability of consensus diagnostic criteria, albeit with some concerns about the practicality of gaining consensus. Two potential approaches to developing consensus criteria were described.

Humans↗

Metabolites with a message: impacts on epigenetics and implications for epimetabopathies.

Once identified primarily as a bioenergetic organelle, the mitochondrion has now emerged as a pivotal signalling hub that communicates with the nucleus to shape cellular fate. It integrates the cell's metabolic state with transcriptional and epigenetic programs, tweaking gene expression. Mitochondrial metabolites serve as regulators of cellular physiology, functioning as important signalling intermediates and modulating enzymes involved in epigenetic modifications. In parallel, nuclear transcriptional programs govern mitochondrial biogenesis, dynamics and quality control to preserve metabolic homeostasis under stress. Moreover, circulating metabolites can function as systemic messengers coordinating interorgan crosstalk and immune responses. Perturbations in this dynamic reciprocity can rewire the cellular script and spiral into "epimetabopathies", where metabolic-epigenetic conflicts ignite pathological conditions. This review discusses how mitochondria-nucleus crosstalk coordinates genome surveillance, metabolite-driven epigenetic regulation and systemic metabolic signalling. It further offers an overview of epimetabopathies with potential implications for future diagnostics and therapeutics.

Humans↗

Metabolic regulation of mitochondrial DNA (mtDNA) homeostasis.

Mitochondria are central hubs of cellular metabolism that harbor their own genome (mtDNA), whose maintenance is essential for both cellular and organismal homeostasis. Unlike nuclear DNA, mtDNA replicates continuously throughout the cell cycle, rendering it particularly sensitive to changes in metabolic state. Emerging evidence indicates that mtDNA homeostasis is not governed solely by dedicated replication factors but is tightly coupled to cellular metabolism. In this review, we discuss how metabolic networks shape mtDNA maintenance through three interconnected layers: mitochondrial nucleotide pools, metabolic control of the replication machinery, and stress-response pathways. This conceptual framework underscores the direct role of metabolic state in governing mtDNA replication, stability, and quality control, with significant implications for mitochondrial disease and therapeutic strategies.

Integrated stress response (ISR)↗

Schwann cells and the pathogenesis of inherited motor and sensory neuropathies (Charcot-Marie-Tooth disease).

Over the last 15 years, a number of mutations in a variety of genes have been identified that lead to inherited motor and sensory neuropathies (HMSN), also called Charcot-Marie-Tooth disease (CMT). In this review we will focus on the molecular and cellular mechanisms that cause the Schwann cell pathologies observed in dysmyelinating and demyelinating forms of CMT. In most instances, the underlying gene defects alter primarily myelinating Schwann cells followed by secondary axonal degeneration. The first set of proteins affected by disease-causing mutations includes the myelin components PMP22, P0/MPZ, Cx32/GJB1, and periaxin. A second group contains the regulators of myelin gene transcription EGR2/Krox20 and SOX10. A third group is composed of intracellular Schwann cells proteins that are likely to be involved in the synthesis, transport and degradation of myelin components. These include the myotubularin-related lipid phosphatase MTMR2 and its regulatory binding partner MTMR13/SBF2, SIMPLE, and potentially also dynamin 2. Mutations affecting the mitochondrial fission factor GDAP1 may indicate an important contribution of mitochondria in myelination or myelin maintenance, whereas the functions of other identified genes, including NDRG1, KIAA1985, and the tyrosyl-tRNA synthase YARS, are not yet clear. Mutations in GDAP1, YARS, and the pleckstrin homology domain of dynamin 2 lead to an intermediate form of CMT that is characterized by moderately reduced nerve conduction velocity consistent with minor myelin deficits. Whether these phenotypes originate in Schwann cells or in neurons, or whether both cell types are directly affected, remains a challenging question. However, based on the advances in systematic gene identification in CMT and the analyses of the function and dysfunction of the affected proteins, crucially interconnected pathways in Schwann cells in health and disease have started to emerge. These networks include the control of myelin formation and stability, membrane trafficking, intracellular protein sorting and quality control, and may extend to mitochondrial dynamics and basic protein biosynthesis.

Animals↗

Mitochondrial DNA control region sequences in Koreans: identification of useful variable sites and phylogenetic analysis for mtDNA data quality control.

We have established a high-quality mtDNA control region sequence database for Koreans. To identify polymorphic sites and to determine their frequencies and haplotype frequencies, the complete mtDNA control region was sequenced in 593 Koreans, and major length variants of poly-cytosine tracts in HV2 and HV3 were determined in length heteroplasmic individuals by PCR analysis using fluorescence-labeled primers. Sequence comparison showed that 494 haplotypes defined by 285 variable sites were found when the major poly-cytosine tract genotypes were considered in distinguishing haplotypes, whereas 441 haplotypes were found when the poly-cytosine tracts were ignored. Statistical parameters indicated that analysis of partial mtDNA control region which encompasses the extended regions of HV1 and HV2, CA dinucleotide repeats in HV3 and nucleotide position 16497, 16519, 456, 489 and 499 (HV1ex+HV2ex+HV3CA+5SNPs) and the analysis of another partial mtDNA control region including extended regions of HV1 and HV2, HV3 region and nucleotide position 16497 and 16519 (HV1ex+HV2ex+HV3+2SNPs) can be used as efficient alternatives for the analysis of the entire mtDNA control region in Koreans. Also, we collated the basic informative SNPs, suggested the important mutation motifs for the assignment of East Asian haplogroups, and classified 592 Korean mtDNAs (99.8%) into various East Asian haplogroups or sub-haplogroups. Haplogroup-directed database comparisons confirmed the absence of any major systematic errors in our data, e.g., a mix-up of site designations, base shifts or mistypings.

Asian People↗

Cell line DNA typing in forensic genetics--the necessity of reliable standards.

The incorporation of reference DNA is crucial to the validation of any DNA typing protocol. This paper aims to provide a panel of reference DNAs for actual forensic profiling strategies, i.e. autosomal and gonosomal STR typing as well as mtDNA sequencing. We have characterised three human lymphoid cell lines, GM9947, GM9948 and GM3657, and considered 58 autosomal and gonosomal microsatellites as well as the mitochondrial control region sequence. Well-established markers and STRs recently developed for forensic use were involved. K562 DNA samples which we purchased from two different suppliers were also analysed. They revealed conflicting results with regard to the ChrX STR marker genotype. Hence, we suggest that K562 is no longer used for the calibration of profiling techniques. Our investigation establishes a panel of one female and two male DNA samples as an STR allelic ladder calibration tool and offers information on six alleles of each autosome (AS) marker, three alleles of each X chromosome (ChrX) marker and two alleles of each ChrY marker. In addition, sequences of the mitochondrial control region of the three DNAs are communicated in order to provide sequencing quality control.

Cell Line, Tumor↗

Repair and regeneration across the lifespan: an ontogenetic perspective.

The capacity for tissue repair and regeneration undergoes a profound and progressive decline across the human lifespan, representing a fundamental driver of aging and chronic disease. This review establishes a comprehensive ontogenetic framework by mapping the continuous biological transition from the flawless, scarless regenerative plasticity of embryonic development to the irreversible fibrotic scarring and organ failure characteristic of senescence. We synthesize the hierarchical collapse of reparative networks across multiple biological scales. Importantly, this ontogenetic decline should not be interpreted as a purely degenerative trajectory but rather as a dynamic systems-level reprogramming in which evolutionary trade-offs prioritize tumor suppression, immune surveillance, and reproductive fitness over long-term regenerative fidelity. Recognizing this adaptive reallocation of biological resources reframes aging not simply as failure but as a predictable recalibration of repair hierarchies. At the molecular and cellular levels, the accumulation of genomic instability, unresolvable DNA damage, and mitochondrial dysfunction gradually overwhelms intracellular quality-control mechanisms. Concurrently, epigenetic drift and chronic, low-grade systemic inflammation ("inflammaging") dismantle the stem cell niche, driving adult stem cell exhaustion and shifting wound healing away from functional tissue replacement toward maladaptive fibrosis. Furthermore, we examine divergent, organ-specific repair trajectories. By contrasting the severe regenerative restrictions of the adult central nervous system and myocardium with the persistent, yet exhaustible, resilience of the liver, we elucidate the unique intrinsic and microenvironmental barriers that impede structural and functional recovery. Finally, we evaluate the clinical paradigm shift from passive management of age-related degeneration to active restoration of tissue integrity. By integrating systemic geroscience-which addresses the global hallmarks of aging-with targeted bioengineering and in vivo epigenetic modulation, contemporary regenerative medicine seeks to recreate permissive, youthful microenvironments. Ultimately, mastering these ontogenetic principles holds unprecedented potential to reactivate endogenous repair pathways, mitigate multi-organ collapse, and significantly extend human functional healthspan.

DNA repair↗