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Mitochondria's primary function is to produce energy through the process of oxidative phosphorylation. ATP synthase is a macromolecular rotary machine located in the inner mitochondrial membrane that catalyzes the synthesis of adenosine triphosphate (ATP) from adenosine diphosphate (ADP) and inorganic phosphate (Pi). The mitochondrial disorders due to ATP synthase deficiency represent a heterogeneous group of diseases characterized by variable severity of the phenotype with onset at birth or later in life till adulthood. Mutations in both, mitochondrial or nucelar DNA encoded genes, may result in ATP synthase impairment, either isolated or combined with deficits of other complexes of oxidative phosphorylation. The aims of the thesis were to characterize TMEM70 protein, an ATP synthase assembly factor, and to analyze the impact of novel disease variants leading to ATP synthase deficiency in patients' derived samples. TMEM70 is a 21 kDa hairpin structure protein localized in the inner mitochondrial membrane, with both termini oriented into the matrix, which forms higher oligomer structures. Our results demonstrated that the absence of TMEM70 protein leads to an isolated deficiency of complex V followed in some stage by adaptive/compensatory effect of respiratory chain complexes. Different severities...

Adult-onset ataxias are a genetically and clinically heterogeneous group of movement disorders. In addition to nuclear gene mutations, sequence changes have also been described in the mitochondrial genome. Here, we present findings of mutation analysis of the mitochondrial gene MT-ATP6. We analyzed 94 patients with adult-onset spinocerebellar ataxia (SCA), including 34 sporadic cases. In all patients, common sequence changes found in SCAs such as repeat expansions and point mutations had been excluded previously. We found pathogenic MT-ATP variants in five of these patients (5.32%), two of whom were sporadic. Four of the five mutations have not previously been described in ataxias. All but one of these mutations affect transmembrane helices of subunit-α of ATP synthase. Two mutations (p.G16S, and p.P18S) disrupt transmembrane helix 1 (TMH1), one mutation (p.G167D) affects TMH5, and another one (p.L217P) TMH6. The fifth mutation (p.T96A) describes an amino acid change in close proximity to transmembrane helix 3 (TMH3). The level of heteroplasmy was either complete or very high ranging from 87 to 99%. The high prevalence of pathogenic MT-ATP6 variants suggests that analysis of this gene should be included in the routine workup of both hereditary and sporadic ataxias.

Mutations in mitochondrial DNA encoded subunit of ATP synthase, MT-ATP6, are frequent causes of neurological mitochondrial diseases with a range of phenotypes from Leigh syndrome and NARP to ataxias and neuropathies. Here we investigated the functional consequences of an unusual heteroplasmic truncating mutation m.9154C>T in MT-ATP6, which caused peripheral neuropathy, ataxia and IgA nephropathy. ATP synthase not only generates cellular ATP, but its dimerization is required for mitochondrial cristae formation. Accordingly, the MT-ATP6 truncating mutation impaired the assembly of ATP synthase and disrupted cristae morphology, supporting our molecular dynamics simulations that predicted destabilized a/c subunit subcomplex. Next, we modeled the effects of the truncating mutation using patient-specific induced pluripotent stem cells. Unexpectedly, depending on mutation heteroplasmy level, the truncation showed multiple threshold effects in cellular reprogramming, neurogenesis and in metabolism of mature motor neurons (MN). Interestingly, MN differentiation beyond progenitor stage was impaired by Notch hyperactivation in the MT-ATP6 mutant, but not by rotenone-induced inhibition of mitochondrial respiration, suggesting that altered mitochondrial morphology contributed to Notch hyperactivation. Finally, we also identified a lower mutation threshold for a metabolic shift in mature MN, affecting lactate utilization, which may be relevant for understanding the mechanisms of mitochondrial involvement in peripheral motor neuropathies. These results establish a critical and disease-relevant role for ATP synthase in human cell fate decisions and neuronal metabolism.

Pathogenic variants that disrupt human mitochondrial protein synthesis are associated with a clinically heterogenous group of diseases. Despite an impairment in oxidative phosphorylation being a common phenotype, the underlying molecular pathogenesis is more complex than simply a bioenergetic deficiency. Currently, we have limited mechanistic understanding on the scope by which a primary defect in mitochondrial protein synthesis contributes to organelle dysfunction. Since the proteins encoded in the mitochondrial genome are hydrophobic and need co-translational insertion into a lipid bilayer, responsive quality control mechanisms are required to resolve aberrations that arise with the synthesis of truncated and misfolded proteins. Here, we show that defects in the OXA1L-mediated insertion of MT-ATP6 nascent chains into the mitochondrial inner membrane are rapidly resolved by the AFG3L2 protease complex. Using pathogenic MT-ATP6 variants, we then reveal discrete steps in this quality control mechanism and the differential functional consequences to mitochondrial gene expression. The inherent ability of a given cell type to recognize and resolve impairments in mitochondrial protein synthesis may in part contribute at the molecular level to the wide clinical spectrum of these disorders.

Introduction Sporadic Parkinson's disease (PD) is a neurodegenerative disorder of unknown etiology. In recent years, it has been established that a genetic component underlies different forms of the disease. For instance, mitochondrial genome variants have been implicated in the pathogenesis of the PD. Aim of the study To determine the association of tRNA(Gln) 4336 and 8701A>G (ATP6: Thr59Ala) mitochondrial DNA polymorphisms with the presence of PD in Mexican mestizo patients. Material and methods This was a cross-sectional study in which patients were recruited from four tertiary-care level hospitals in Mexico. Genotyping was performed using real-time PCR with TaqMan genotyping assays. Genotypes were confirmed by automated sequencing. Results The 4336C allele of the tRNAGln gene was present at a low frequency, and the 8701G allele of the MT-ATP6 gene was not associated with PD. Conclusions The 4336C variant of the tRNAGln gene was uncommon in the study population, and 8701A/G of MT-ATP6 was not associated with PD in Mexican Mestizos.

Diagnosing complex V deficiencies caused by new variants in mitochondrial DNA is challenging due to the rarity, phenotypic diversity, and limited functional assessments. We describe a child with the m.9032T > C variant in MT-ATP6 encoding p.(Leu169Pro), with primary presentation of microcephaly, ataxia, hearing loss, and lactic acidosis. Functional studies reveal abnormal fragment F1 of complex V on blue native gel electrophoresis. Respirometry showed excessively tight coupling through complex V depressing oxygen consumption upon ADP stimulation and an excessive increase following uncoupling, in the presence of upregulation of mitochondrial biogenesis. These data add evidence about pathogenicity and functional impact of this variant.

Introduction: Episodic muscle weakness is the hallmark of a heterogeneous group of disorders known as periodic paralysis. A majority are due to single nucleotide mutations causing membrane depolarization. Methods: We report 2 family members with chronic, slowly progressive, distal axonal neuropathy or Charcot-Marie-Tooth disease type 2 (CMT2) and episodic weakness resembling periodic paralysis. Results: Next generation sequencing (NGS) identified a mitochondrial MT-ATP6 mutation m.9185T>C (p.Leu220Pro) in both patients, consistent with a previous report of an association with this phenotype. The episodic weakness has been responsive to acetazolamide therapy for a few decades. By contrast, the underlying axonal neuropathy is quite progressive despite treatment with acetazolamide. Conclusions: Mitochondrial DNA mutations should be considered in patients with a history of episodic weakness and axonal inherited neuropathy (CMT2). The episodic weakness is responsive to acetazolamide therapy, and electrophysiological testing for periodic paralysis with a long exercise protocol is negative in these cases. This article is protected by copyright. All rights reserved.

To address the frequency of complex V defects, we systematically sequenced MT-ATP6/8 genes in 512 consecutive patients. We performed functional analysis in muscle or fibroblasts for 12 out of 27 putative homoplasmic mutations and in cybrids for four. Fibroblasts, muscle and cybrids with known deleterious mutations underwent parallel analysis. It included oxidative phosphorylation spectrophotometric assays, western blots, structural analysis, ATP production, glycolysis and cell proliferation evaluation. We demonstrated the deleterious nature of three original mutations. Striking gradation in severity of the mutations consequences and differences between muscle, fibroblasts and cybrids implied a likely under-diagnosis of human complex V defects.

Mitochondrial (mt) DNA haplogroups, defined by specific single nucleotide polymorphism (SNP) patterns, represent populations of diverse geographic origins and have been associated with increased risk or protection of many diseases. The H haplogroup is the most common European haplogroup while the K haplogroup is highly associated with the Ashkenazi Jewish population. Transmitochondrial cybrids (cell lines with identical nuclei, but mtDNA from either H (n = 8) or K (n = 8) subjects) were analyzed by the Seahorse flux analyzer, quantitative polymerase chain reaction (Q-PCR) and immunohistochemistry (IHC). Cybrids were treated with amyloid-β peptides and cell viabilities were measured. Other cybrids were demethylated with 5-aza-2′-deoxycytidine (5-aza-dC) and expression levels for APOE and NFkB2 were measured. Results show K cybrids have (a) significantly lower mtDNA copy numbers, (b) higher expression levels for MT-DNA encoded genes critical for oxidative phosphorylation, (c) lower Spare Respiratory Capacity, (d) increased expression of inhibitors of the complement pathway and important inflammasome-related genes; and (e) significantly higher levels of APOE transcription that were independent of methylation status. After exposure to amyloid-β1–42 peptides (active form), H haplogroup cybrids demonstrated decreased cell viability compared to those treated with amyloid-β42–1 (inactive form) (p < 0.0001), while this was not observed in the K cybrids (p = 0.2). K cybrids had significantly higher total global methylation levels and differences in expression levels for two acetylation genes and four methylation genes. Demethylation with 5-aza-dC altered expression levels for NFkB2, while APOE transcription patterns were unchanged. Our findings support the hypothesis that mtDNA-nuclear retrograde signaling may mediate expression levels of APOE, a key factor in many age-related diseases. Future studies will focus on identification of the mitochondrial-nuclear retrograde signaling mechanism(s) contributing to these mtDNA-mediated differences.

Background: Adaptation and natural selection serve as an important part of evolution. Adaptation in molecular level can lead to genetic drift which causes mutation of genetic material; one of which is polymorphism of mitochondrial DNA (mtDNA). The aim of this study is to verify the polymorphism of mitochondrially-encoded Adenosine Triphosphate synthase6gene (MT-ATP6) as one of mtDNA building blocks among tropic, sub-tropic, and polar areas. Methods: This descriptive quantitative research used 3,210 mtDNA sequences, taken from GenBank, as secondary data from 27 different populations. The data were grouped into 3 population groups based on the climates of their location. After grouping, the sequences were then aligned and trimmed using Unipro EUGENE, and analysed by Arlequin and MitoTool. Results: Results demonstrated 21 haplotypes distributed among 3 populations with variations between each climate population. In the tropic and sub-tropic populations, the dominant haplotype is h1 while h6 is dominant in the polar population. Conclusions: There is a variation of haplotype polymorphism between tropic, sub-tropic, and polar climate population.

Despite improvements in treatment strategies, colorectal cancer (CRC) still has high mortality rates. Most CRCs develop from adenopolyps via the adenoma-carcinoma sequence. A mechanism for inhibition of this sequence in individuals with a high risk of developing CRC is urgently needed. Differential studies of mitochondrial (mt) gene expressions in the progressive stages of CRC with villous architecture are warranted to reveal early risk assessments and new targets for chemoprevention of the disease. In the present study, reverse transcription-quantitative PCR (RT-qPCR) was used to determine the relative amount of the transcripts of six mt genes [MT-RNR1, MT-ND1, MT-COI, MT-ATP6, MT-ND6, and MT-CYB (region 648–15887)] which are involved in the normal metabolism of mitochondria. A total of 42 pairs of tissue samples obtained from colorectal adenopolyps, adenocarcinomas, and their corresponding adjacent normal tissues were examined. Additionally, electron transport chain (ETC), complexes I (NADH: ubiquinone oxidoreductase) and III (CoQH2-cytochrome C reductase), and carbonyl protein group contents were analyzed. Results indicate that there were differential expressions of the six mt genes and elevated carbonyl protein contents among the colorectal adenopolyps compared to their paired adjacent normal tissues (p < 0.05). The levels of complexes I and III were higher in tumor tissues relative to adjacent normal tissues. Noticeably, the expression of MT-COI was overexpressed in late colorectal carcinomas among all studied transcripts. Our data suggest that increased expressions in certain mt genes and elevated levels of ROS may potentially play a critical role in the colorectal tumors evolving from adenopolyps to malignant lesions.

With the advent of next generation sequencing, the list of mitochondrial DNA (mtDNA) mutations identified in patients rapidly and continuously expands. They are frequently found in a limited number of cases, sometimes a single individual (as with the case herein reported) and in heterogeneous genetic backgrounds (heteroplasmy), which makes it difficult to conclude about their pathogenicity and functional consequences. As an organism amenable to mitochondrial DNA manipulation, able to survive by fermentation to loss-of-function mtDNA mutations, and where heteroplasmy is unstable, Saccharomyces cerevisiae is an excellent model for investigating novel human mtDNA variants, in isolation and in a controlled genetic context. We herein report the identification of a novel variant in mitochondrial ATP6 gene, m.8909T>C. It was found in combination with the well-known pathogenic m.3243A>G mutation in mt-tRNALeu. We show that an equivalent of the m.8909T>C mutation compromises yeast adenosine tri-phosphate (ATP) synthase assembly/stability and reduces the rate of mitochondrial ATP synthesis by 20–30% compared to wild type yeast. Other previously reported ATP6 mutations with a well-established pathogenicity (like m.8993T>C and m.9176T>C) were shown to have similar effects on yeast ATP synthase. It can be inferred that alone the m.8909T>C variant has the potential to compromise human health.

Leigh Syndrome (LS) is a rare, hereditary progressive neurodegenerative disorder of infancy or early childhood associated with a highly variable clinical presentation even among siblings. Further, genetic heterogeneity makes its diagnosis complicated. Its causative genetic variations are notified in some of the mitochondrial and nuclear genes. Here, we report an atypical case of LS in a 9-year-old boy associated with a novel variation in MT-ATP6 gene. The atypical findings were Bilateral Basal Ganglia Calcification (BGC) and late survival age in the patient. Analyses of the Whole Mitochondrial Genome Sequencing (WMGS) results of the recruited patient and his mother at different read coverage, first at 100× and later repeated at 500×, revealed a novel disease-associated variation in the already known disease-associated MT-ATP6 gene. In conclusion, the present study indicates amalgamation of both neuro-imaging and Next Generation Sequencing (NGS) Technologies aiding the proper diagnosis of LS in atypical cases.

Mitochondrial DNA mutations at MT-ATP6 gene are relatively common in individuals suffering from striatal necrosis syndromes. These patients usually do not show apparent histochemical and/or biochemical signs of oxidative phosphorylation dysfunction. Because of this, MT-ATP6 is not typically analyzed in many other mitochondrial disorders that have not been previously associated to mutations in this gene. To correct this bias, we have performed a screening of the MT-ATP6 gene in a large collection of patients suspected of suffering different mitochondrial DNA (mtDNA) disorders. In three cases, biochemical, molecular-genetics and other analyses in patient tissues and cybrids were also carried out. We found three new pathologic mutations. Two of them in patients showing phenotypes that have not been commonly associated to mutations in the MT-ATP6 gene. These results remark the importance of sequencing the MT-ATP6 gene in patients with striatal necrosis syndromes, but also within other mitochondrial pathologies. This gene should be sequenced at least in all those patients suspected of suffering an mtDNA disorder disclosing normal results for histochemical and biochemical analyses of respiratory chain.

Objective: To report that homoplasmic deleterious mutations in the mitochondrial DNA MT-ATP6/8 genes may be responsible for acute episodes of limb weakness mimicking periodic paralysis due to channelopathies and dramatically responding to acetazolamide. Methods: Mitochondrial DNA sequencing and restriction PCR, oxidative phosphorylation functional assays, reactive oxygen species metabolism, and patch-clamp technique in cultured skin fibroblasts. Results: Occurrence of a typical MELAS (mitochondrial encephalopathy with lactic acidosis and stroke-like episodes) syndrome in a single member of a large pedigree with episodic weakness associated with a later-onset distal motor neuropathy led to the disclosure of 2 deleterious mitochondrial DNA mutations. The MT-ATP6 m.9185T>C p.Leu220Pro mutation, previously associated with Leigh syndrome, was present in all family members, while the MT-TL1 m.3271T>C mutation, a known cause of MELAS syndrome, was observed in the sole patient with MELAS presentation. Significant defect of complexes V and I as well as oxidative stress were observed in both primary fibroblasts and cybrid cells with 100% m.9185T>C mutation. Permanent plasma membrane depolarization and altered permeability to K + in fibroblasts provided a link with the paralysis episodes. Screening of 9 patients, based on their clinical phenotype, identified 4 patients with similar deleterious MT-ATP6 mutations (twice m.9185T>C and once m.9176T>C or m.8893T>C). A fifth patient presented with an original potentially deleterious MT-ATP8 mutation (m.8403T>C). All mutations were associated with almost-normal complex V activity but significant oxidative stress and permanent plasma membrane depolarization. Conclusion: Homoplasmic mutations in the MT-ATP6/8 genes may cause episodic weakness responding to acetazolamide treatment.

We describe a novel frameshift mutation in the mitochondrial ATP6 gene in a 4-year-old girl associated with ataxia, microcephaly, developmental delay and intellectual disability. A heteroplasmic frameshift mutation in the MT-ATP6 gene was confirmed in the patient's skeletal muscle and blood. The mutation was not detectable in the mother's DNA extracted from blood or buccal cells. Enzymatic and oxymetric analysis of the mitochondrial respiratory system in the patients' skeletal muscle and skin fibroblasts demonstrated an isolated complex V deficiency. Native PAGE with subsequent immunoblotting for complex V revealed impaired complex V assembly and accumulation of ATPase subcomplexes. Whilst northern blotting confirmed equal presence of ATP8/6 mRNA, metabolic S-35-labelling of mitochondrial translation products showed a severe depletion of the ATP6 protein together with aberrant translation product accumulation. In conclusion, this novel isolated complex V defect expands the clinical and genetic spectrum of mitochondrial defects of complex V deficiency. Furthermore, this work confirms the benefit of native PAGE as an additional diagnostic method for the identification of OXPHOS defects, as the presence of complex V subcomplexes is associated with pathogenic mutations of mtDNA. (C) 2017 Elsevier Masson SAS. All rights reserved.

BACKGROUND Prostate cancer is one of the commonest cancers worldwide and is responsible for nearly 6% of all male cancer deaths. Despite this relevance, the mechanisms involved in the development and progression of this malignancy remain unknown. The involvement of polypeptides of the mitochondrial respiratory chain, the Krebs cycle and the glutathione antioxidant system in this type of cancer has been previously described, although no publication has focused on the expression of mitochondrial genes in the prostate of PCa patients. METHODS We have determined by reverse transcription-quantitative PCR (RT-qPCR) the relative amount of the transcripts of eight mitochondrial genes (MT-ND2, MT-ND4, MT-ND6, MT-CYB, 12S/MT-RNR1, 16S/MT-RNR2, MT-CO2/COX2, MT-ATP6), and four nuclear genes (COX11, GSR, CS, ACO2), all of them key players in the normal metabolism of mitochondria. Additionally we analyzed the expression of Cyclophilin A (PPIA). RESULTS We observed differential expression of mitochondrial 12S/MT-RNR1, MT-CO2/COX2, and MT-ATP6 transcripts in tumor samples when compared to their paired normal samples. CONCLUSIONS The amount of mitochondrial 12S/MT-RNR1, MT-CO2/COX2, and MT-ATP6 transcripts is significantly decreased in tumor samples when compared to their paired normal sample, suggesting that mitochondrial gene expression is altered in PCa. Prostate 68:1086–1096, 2008. © 2008 Wiley-Liss, Inc.

Since the discovery of somatic mtDNA mutations in tumor cells, multiple studies have focused on establishing a causal relationship between those changes and alterations in energy metabolism, a hallmark of cancer cells. Yet the consequences of these mutations on mitochondrial function remain largely unknown. In this study, Saccharomyces cerevisiae has been used as a model to investigate the functional consequences of four cancer-associated missense mutations (8914C>A, 8932C>T, 8953A>G, 9131T>C) found in the mitochondrial MT-ATP6 gene. This gene encodes the a-subunit of F1FO-ATP synthase, which catalyzes the last steps of ATP production in mitochondria. Although the four studied mutations affected well-conserved residues of the a-subunit, only one of them (8932C>T) had a significant impact on mitochondrial function, due to a less efficient incorporation of the a-subunit into ATP synthase. Our findings indicate that these ATP6 genetic variants found in human tumors are neutral mitochondrial genome substitutions with a limited, if any, impact on the energetic function of mitochondria.

Purpose To investigate the association of mutations in the mitochondrial DNA (mtDNA) or nuclear candidate genes with mitochondrial disease-related ophthalmic manifestations (nystagmus, ptosis, ophthalmoplegia, optic neuropathy and retinopathy) in children. Methods A retrospective cohort of children (n = 98) was identified from the medical record files of a tertiary care hospital. The entire mtDNA and nuclear genes POLG1, OPA1 and PEO1 were analysed from the available DNA samples (n = 38). Furthermore, some nuclear candidate genes were investigated based on family history and phenotype. Rare mtDNA mutations were evaluated using in silico predictors and sequence alignment. Results Three patients had previously identified mutations in mtDNA that are associated with optic neuropathy (in MT-ND6 and MT-ND1) and nystagmus (in tRNA Arg). Nine rare mutations in MT-ATP6 were identified in seven patients, of whom four manifested with retinopathy and three had clusters of MT-ATP6 mutations. Nuclear PEO1 and OPA1 were unchanged in all samples, but a patient with nystagmus had a heterozygous POLG1 mutation. The analysis of nuclear candidate genes revealed mutations in NDUF8 (patient with nystagmus), TULP1 (patient with optic neuropathy, nystagmus and retinopathy) and RP2 (patient with retinopathy) genes. Conclusions Children with retinopathy, nystagmus or optic neuropathy, especially together with developmental delay or positive family history, should be considered for mitochondrial disease. MT-ATP6 should be taken into account for children with retinopathy of unknown aetiology.

Objective: Charcot-Marie-Tooth (CMT) disease is the most common inherited neuromuscular disorder, affecting 1 in 2,500 individuals. Mitochondrial DNA (mtDNA) mutations are not generally considered within the differential diagnosis of patients with uncomplicated inherited neuropathy, despite the essential requirement of ATP for axonal function. We identified the mtDNA mutation m.9185T>C in MT-ATP6 , encoding the ATP6 subunit of the mitochondrial ATP synthase (OXPHOS complex V), at homoplasmic levels in a family with mitochondrial disease in whom a severe motor axonal neuropathy was a striking feature. This led us to hypothesize that mutations in the 2 mtDNA complex V subunit encoding genes, MT-ATP6 and MT-ATP8 , might be an unrecognized cause of isolated axonal CMT and distal hereditary motor neuropathy (dHMN). Methods: A total of 442 probands with CMT type 2 (CMT2) (270) and dHMN (172) were screened for MT-ATP6/8 mutations after exclusion of mutations in known CMT2/dHMN genes. Mutation load was quantified using restriction endonuclease analysis. Blue-native gel electrophoresis (BN-PAGE) was performed to analyze the effects of m.9185T>C on complex V structure and function. Results: Three further probands with CMT2 harbored the m.9185T>C mutation. Some relatives had been classified as having dHMN. Patients could be separated into 4 groups according to their mutant m.9185T>C levels. BN-PAGE demonstrated both impaired assembly and reduced activity of the complex V holoenzyme. Conclusions: We have shown that m.9185T>C in MT-ATP6 causes CMT2 in 1.1% of genetically undefined cases. This has important implications for diagnosis and genetic counseling. Recognition that mutations in MT-ATP6 cause CMT2 enhances current understanding of the pathogenic basis of axonal neuropathy.

Devastating human neuromuscular disorders have been associated to defects in the ATP synthase. This enzyme is found in the inner mitochondrial membrane and catalyzes the last step in oxidative phosphorylation, which provides aerobic eukaryotes with ATP. With the advent of structures of complete ATP synthases, and the availability of genetically approachable systems such as the yeast Saccharomyces cerevisiae, we can begin to understand these molecular machines and their associated defects at the molecular level. In this review, we describe what is known about the clinical syndromes induced by 58 different mutations found in the mitochondrial genes encoding membrane subunits 8 and a of ATP synthase, and evaluate their functional consequences with respect to recently described cryo-EM structures.

Among mitochondrial diseases, isolated complex V (CV) deficiency represents a rare cause of respiratory chain (RC) dysfunction. In mammalian mitochondrial DNA (mtDNA), MT-ATP6 partly overlaps with MT-ATP8 making double mutations possible, yet extremely rarely reported principally in patients with cardiomyopathy. Here, we report a novel m.8561 C>T substitution in the overlapping region of MT-ATP6 and MT-ATP8 in a child with early-onset ataxia, psychomotor delay and microcephaly, enlarging the clinical manifestations spectrum associated with CV deficiency.

Distinct clinical syndromes have been associated with pathogenic MT-ATP6 variants. In this cohort study, we identified 125 individuals (60 families) including 88 clinically affected individuals and 37 asymptomatic carriers. Thirty-one individuals presented with Leigh syndrome and 7 with neuropathy ataxia retinitis pigmentosa. The remaining 50 patients presented with variable nonsyndromic features including ataxia, neuropathy, and learning disability. We confirmed maternal inheritance in 39 families and demonstrated that tissue segregation patterns and phenotypic threshold are variant dependent. Our findings suggest that MT-ATP6-related mitochondrial DNA disease is best conceptualized as a mitochondrial disease spectrum disorder and should be routinely included in genetic ataxia and neuropathy gene panels. ANN NEUROL 2019;86:310-315.