Pyruvate dehydrogenase E1α deficiency in a family : Different clinical presentation in two siblings

The pyruvate dehydrogenase (PDH) complex (PDHc) is responsible for the irreversible conversion of pyruvate to acetyl-CoA. PDHc is a multienzyme complex consisting of three catalytic subunits, pyruvate decarboxylase (E1), dihydrolipoamideacetyltransferase (E2), dihydrolipoamide dehydrogenase (E3), and two regulatorysubunits, E1 kinase and phospho-E1 phosphatase. An abnormal E1asubunit, whosegene is located on the X chromosome, is the most frequent cause of PDH deÐciency. The clinical presentation of a PDH-E1adeÐciency (McKusick 312170) is variable.We have analysed a family with a mutation (36 bp insertion in exon 10) in thePDH-E1agene in which the male member had a diferent and less severe clinicalpicture than his afected sister.Facultad de Ciencias Médica

Karakterističan fenotip u djevojčice s Rettovim sindromom i delecijom 25 bp zbog nove mutacije u 4. eksonu (.881_905del25, nm_004992.3) gena MECP2

Rett syndrome is a pervasive developmental disorder with a variable clinical presentation, which is caused by point mutations or large deletions/duplications in the X-linked methyl-CpG-binding protein 2 (MECP2) gene. The aim is to describe variation in the clinical course related to the mutation identifi ed in exon 4 of the MECP2 gene. Retrospective review of data, electroencephalography and treatment was done in a 19-year-old girl previously diagnosed with a MECP2 gene mutation. Born after an uneventful pregnancy, the female patient’s growth and psychomotor development were normal, except for delayed speech. At the age of 3 years, tonic-clonic seizures started and at the age of 3.5 years autistic behavior was observed, followed by rapid mental deterioration, loss of speech and motor skills, with periods of hyperventilation. At the age of 5 years, she showed occasionally „hand-washing“ movements. Extensive neuro-metabolic investigation was nondiagnostic. Genetic analysis revealed a novel 25 bp deletion mutation in exon 4 (c.881_905del25) of the MECP2 gene. Until now, multiple epileptic seizure types, refractory to all antiepileptic polytherapy and with normal video EEG background, have occurred daily. She is spastic and ataxic, but still able to walk slowly with a wide based gait. In this female patient, the onset of symptoms manifested much later than encountered in typical cases of Rett syndrome. Epilepsy with daily frequency is however drug resistant. Unexpectedly, she is still able to walk at the age of 19 years. A genotype-phenotype correlation is suspected.Rettov sindrom (RTT) pervazivni je razvojni poremećaj s različitim kliničkim slikama, a uzrokovan najčešće točkastim mutacijama ili delecijom/duplikacijom metil-CpG-vezanog proteina 2 (MECP2) na genu X. Cilj je opisati različitosti kliničkog tijeka bolesti koje su vezane za nađenu mutaciju na 4. eksonu gena MECP2. Retrospektivna analiza anamnestičkih podataka, electroencefalograma i liječenja kod 19-godišnje djevojke s nalazom mutacije na genu MECP2. Djevojčica je rođena nakon uredne trudnoće kao 4. dijete u obitelji, rast i psihomotorni razvoj su bili uredni, osim zaostatka u razvoju govora. Sa 3 godine započeli su toničko-klonički grčevi, a sa 3,5 godine uočava se autistično ponašanje, nakon čega je uslijedila mentalna deterioracija s prestankon govora, smetnjama motorike i povremenim kratkotrajnim javljanjima hiperventilacije. Sa 5 godina povremeno su se uočavali pokreti „pranja ruku“. Velikim opsegom neurometaboličkih pretraga nije se našao uzrok smetnjama. Genetičkom analizom nađena je delecija 25 bp kao jedna od novih mutacija u 4. eksonu (c.881_905del25) gena MECP2. Uslijedili su razni oblici epileptičkih napadaja koji su bili tvrdokorni na antiepileptičku terapiju, uz urednu osnovnu aktivnost na video-elektroencefalogramu. Djevojka ima povišen mišićni tonus, ataktičan hod i može samostalno hodati na širokoj osnovi. U ove djevojke simptomi su počeli kasnije nego u tipičnim slučajevima Rettovog sindroma. Epileptički napadaji su svakodnevni i tvrdokorni na terapiju, a 19-godišnja djevojka još hoda, a najvjerojatniji razlog je međusobna povezanost genotipa i fenotipa

Translation of MT-ATP6 pathogenic variants reveals distinct regulatory consequences from the co-translational quality control of mitochondrial protein synthesis

ddab314Pathogenic variants that disrupt human mitochondrial protein synthesis are associated with a clinically heterogeneous 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.Peer reviewe

A bumpy ride on the diagnostic bench of massive parallel sequencing, the case of the mitochondrial genome

The advent of massive parallel sequencing (MPS) has revolutionized the field of human molecular genetics, including the diagnostic study of mitochondrial (mt) DNA dysfunction. The analysis of the complete mitochondrial genome using MPS platforms is now common and will soon outrun conventional sequencing. However, the development of a robust and reliable protocol is rather challenging. A previous pilot study for the re-sequencing of human mtDNA revealed an uneven coverage, affecting predominantly part of the plus strand. In an attempt to address this problem, we undertook a comparative study of standard and modified protocols for the Ion Torrent PGM system. We could not improve strand representation by altering the recommended shearing methodology of the standard workflow or omitting the DNA polymerase amplification step from the library construction process. However, we were able to associate coverage bias of the plus strand with a specific sequence motif. Additionally, we compared coverage and variant calling across technologies. The same samples were also sequenced on a MiSeq device which showed that coverage and heteroplasmic variant calling were much improved

Pyruvate dehydrogenase E1α deficiency in a family : Different clinical presentation in two siblings

The pyruvate dehydrogenase (PDH) complex (PDHc) is responsible for the irreversible conversion of pyruvate to acetyl-CoA. PDHc is a multienzyme complex consisting of three catalytic subunits, pyruvate decarboxylase (E1), dihydrolipoamideacetyltransferase (E2), dihydrolipoamide dehydrogenase (E3), and two regulatorysubunits, E1 kinase and phospho-E1 phosphatase. An abnormal E1asubunit, whosegene is located on the X chromosome, is the most frequent cause of PDH deÐciency. The clinical presentation of a PDH-E1adeÐciency (McKusick 312170) is variable.We have analysed a family with a mutation (36 bp insertion in exon 10) in thePDH-E1agene in which the male member had a diferent and less severe clinicalpicture than his afected sister.Facultad de Ciencias Médica

Leigh syndrome followed by parkinsonism in an adult with homozygous c.626C > T mutation in MTFMT

Objective : To report the clinical, radiologic, biochemical, and molecular characteristics in a 46-year-old participant with adult-onset Leigh syndrome (LS), followed by parkinsonism. Methods : Case description with diagnostic workup included blood and CSF analysis, skeletal muscle investigations, blue native polyacrylamide gel electrophoresis, whole exome sequencing targeting nuclear genes involved in mitochondrial transcription and translation, cerebral MRI, 123I-FP-CIT brain single-photon emission computed tomography (SPECT), and C-11 raclopride positron emission tomography (PET). Results : The participant was found to have a defect in the oxidative phosphorylation caused by a c.626C>T mutation in the gene coding for mitochondrial methionyl-tRNA formyltransferase (MTFMT), which is a pathogenic mutation affecting intramitochondrial protein translation. The proband had a normal concentration of lactate in blood and no abnormal microscopic findings in skeletal muscle. Cerebral MRI showed bilateral lesions in the striatum, mesencephalon, pons, and medial thalamus. Lactate concentration in CSF was increased. FP-CIT SPECT and C-11 raclopride PET demonstrated a defect in the dopaminergic system. Conclusions : We report on a case with adult-onset LS related to a MTFMT mutation. Two years after the onset of symptoms of LS, the proband developed a parkinson-like disease. The c.626C>T mutation is the most common pathogenic mutation found in 22 patients reported earlier in the literature with a defect in MTFMT. The age of the previously reported cases varied between 14 months and 24 years. Our report expands the phenotypical spectrum of MTFMT-related neurologic disease and provides clinical evidence for involvement of MTFMT in extrapyramidal syndromes

Mild myopathic phenotype in a patient with homozygous c.416C > T mutation in TK2 gene

The mitochondrial DNA depletion syndrome (MDDS) is characterized by extensive phenotypic variability and is due to nuclear gene mutations resulting in reduced mtDNA copy number. Thymidine kinase 2 (TK2) mutations are well known to be associated with MDDS. Few severely affected cases carrying the c.416C > T mutation in TK2 gene have been described so far. We describe the case of a 14months boy with the aforementioned TK2 gene pathogenic mutation at a homozygous state, presenting with a mild clinical phenotype. In addition to severe mitochondrial pathology on muscle biopsy, there was also histochemical evidence of adenylate deaminase deficiency. Overall, this report serves to further expand the clinical spectrum of TK2 mutations associated with MDDS

Differential proteomic profiling unveils new molecular mechanisms associated with mitochondrial complex III deficiency

We have analyzed the cellular pathways and metabolic adaptations that take place in primary skin fibroblasts from patients with mutations in BCS1L, a major genetic cause of mitochondrial complex III enzyme deficiency. Mutant fibroblasts exhibited low oxygen consumption rates and intracellular ATP levels, indicating that the main altered molecular event probably is a limited respiration-coupled ATP production through the OXPHOS system. Two-dimensional DIGE and MALDI-TOF/TOF mass spectrometry analyses unambiguously identified 39 proteins whose expression was significantly altered in complex III-deficient fibroblasts. Extensive statistical and cluster analyses revealed a protein profile characteristic for the BCS1L mutant fibroblasts that included alterations in energy metabolism, cell signaling and gene expression regulation, cytoskeleton formation and maintenance, and intracellular stress responses. The physiological validation of the predicted functional adaptations of human cultured fibroblasts to complex III deficiency confirmed the up-regulation of glycolytic enzyme activities and the accumulation of branched-chain among other amino acids, suggesting the activation of anaerobic glycolysis and cellular catabolic states, in particular protein catabolism, together with autophagy as adaptive responses to mitochondrial respiratory chain dysfunction and ATP deficiency. Our data point to an overall metabolic and genetic reprogramming that could contribute to explain the clinical manifestations of complex III deficiency in patientsThis work was funded by Instituto de Salud Carlos III (grant numbers PI11-00182 to C.U., PS09-01359 to M.A.M., CP11-00151 to M.M., and PI12-00933 to S.C.), by Comunidad Autónoma de Madrid (P2010/BMD-2361 to C.U. and P2010/BMD-2402 to M.A.M. and S.C.) and by NIH-NIGMS (1R01GM105781-01 to C.U.

Development of a human mitochondrial oligonucleotide microarray (h-MitoArray) and gene expression analysis of fibroblast cell lines from 13 patients with isolated F1Fo ATP synthase deficiency

<p>Abstract</p> <p>Background</p> <p>To strengthen research and differential diagnostics of mitochondrial disorders, we constructed and validated an oligonucleotide microarray (h-MitoArray) allowing expression analysis of 1632 human genes involved in mitochondrial biology, cell cycle regulation, signal transduction and apoptosis. Using h-MitoArray we analyzed gene expression profiles in 9 control and 13 fibroblast cell lines from patients with F₁F_oATP synthase deficiency consisting of 2 patients with mt9205ΔTA microdeletion and a genetically heterogeneous group of 11 patients with not yet characterized nuclear defects. Analysing gene expression profiles, we attempted to classify patients into expected defect specific subgroups, and subsequently reveal group specific compensatory changes, identify potential phenotype causing pathways and define candidate disease causing genes.</p> <p>Results</p> <p>Molecular studies, in combination with unsupervised clustering methods, defined three subgroups of patient cell lines – M group with mtDNA mutation and N1 and N2 groups with nuclear defect. Comparison of expression profiles and functional annotation, gene enrichment and pathway analyses of differentially expressed genes revealed in the M group a transcription profile suggestive of synchronized suppression of mitochondrial biogenesis and G1/S arrest. The N1 group showed elevated expression of complex I and reduced expression of complexes III, V, and V-type ATP synthase subunit genes, reduced expression of genes involved in phosphorylation dependent signaling along MAPK, Jak-STAT, JNK, and p38 MAP kinase pathways, signs of activated apoptosis and oxidative stress resembling phenotype of premature senescent fibroblasts. No specific functionally meaningful changes, except of signs of activated apoptosis, were detected in the N2 group. Evaluation of individual gene expression profiles confirmed already known <it>ATP6/ATP8 </it>defect in patients from the M group and indicated several candidate disease causing genes for nuclear defects.</p> <p>Conclusion</p> <p>Our analysis showed that deficiency in the ATP synthase protein complex amount is generally accompanied by only minor changes in expression of ATP synthase related genes. It also suggested that the site (mtDNA vs nuclear DNA) and the severity (ATP synthase content) of the underlying defect have diverse effects on cellular gene expression phenotypes, which warrants further investigation of cell cycle regulatory and signal transduction pathways in other OXPHOS disorders and related pharmacological models.</p