RESUMEN
BACKGROUND: Variants in POLG are one of the most common causes of inherited mitochondrial disease. Phenotypic classification of POLG disease has evolved haphazardly making it complicated and difficult to implement in everyday clinical practise. The aim of our study was to simplify the classification and facilitate better clinical recognition. METHODS: A multinational, retrospective study using data from 155 patients with POLG variants recruited from seven European countries. RESULTS: We describe the spectrum of clinical features associated with POLG variants in the largest known cohort of patients. While clinical features clearly form a continuum, stratifying patients simply according to age of onset-onset prior to age 12 years; onset between 12 and 40 years and onset after the age of 40 years, permitted us to identify clear phenotypic and prognostic differences. Prior to 12 years of age, liver involvement (87%), seizures (84%), and feeding difficulties (84%) were the major features. For those with onset between 12 and 40 years, ataxia (90%), peripheral neuropathy (84%), and seizures (71%) predominated, while for those with onset over 40 years, ptosis (95%), progressive external ophthalmoplegia (89%), and ataxia (58%) were the major clinical features. The earlier the onset the worse the prognosis. Patients with epilepsy and those with compound heterozygous variants carried significantly worse prognosis. CONCLUSION: Based on our data, we propose a simplified POLG disease classification, which can be used to guide diagnostic investigations and predict disease course.
Asunto(s)
ADN Polimerasa gamma/genética , Predisposición Genética a la Enfermedad/genética , Enfermedades Mitocondriales/clasificación , Enfermedades Mitocondriales/genética , Adolescente , Adulto , Edad de Inicio , Anciano , Anciano de 80 o más Años , Niño , Preescolar , Europa (Continente) , Femenino , Humanos , Lactante , Masculino , Persona de Mediana Edad , Enfermedades Mitocondriales/mortalidad , Mutación , Estudios Retrospectivos , Análisis de Supervivencia , Adulto JovenRESUMEN
Mitochondrial respiratory chain complex I consists of 44 different subunits and contains 3 functional modules: the Q-, the N- and the P-module. NDUFA9 is a Q-module subunit required for complex I assembly or stability. However, its role in complex I biogenesis has not been studied in patient fibroblasts. So far, a single patient carrying an NDUFA9 variant with a severe neonatally fatal phenotype has been reported. Via exome sequencing, we identified a novel homozygous NDUFA9 missense variant in another patient with a milder phenotype including childhood-onset progressive generalized dystonia and axonal peripheral neuropathy. We performed complex I assembly analysis using primary skin fibroblasts of both patients. Reduced complex I abundance and an accumulation of Q-module subassemblies were present in both patients but more pronounced in the severe clinical phenotype patient. The latter displayed additional accumulation of P-module subassemblies, which was not present in the milder-phenotype patient. Lentiviral complementation of both patient fibroblast cell lines with wild-type NDUFA9 rescued complex I deficiency and the assembly defects. Our report further characterizes the phenotypic spectrum of NDUFA9 deficiency and demonstrates that the severity of the clinical phenotype correlates with the severity of the effects of the different NDUFA9 variants on complex I assembly.
Asunto(s)
Complejo I de Transporte de Electrón/genética , Proteínas Mitocondriales/genética , Mutación Puntual , Células Cultivadas , Complejo I de Transporte de Electrón/metabolismo , Resultado Fatal , Células HEK293 , Humanos , Recién Nacido , Masculino , Proteínas Mitocondriales/metabolismo , Secuenciación del Exoma/métodosRESUMEN
The inherited optic neuropathies comprise a group of genetically heterogeneous disorders causing optic nerve dysfunction. In some cases, optic neuropathies are associated with cerebellar atrophy which mainly affects the vermis. Here, we describe a Moroccan girl of consanguineous parents with optic atrophy and cerebellar atrophy. Exome sequencing revealed a novel homozygous mutation (c.283+3G>T) in the donor splice site for exon 1 of SLC25A46. RNA analysis revealed that an alternative splice site within exon 1 was used leading to a premature termination codon within exon 2. SLC25A46 mRNA expression showed there is no wild-type transcript present in the patient and the mutant transcript does not undergo nonsense-mediated mRNA decay. Futhermore, we observed c.283+3G>T SLC25A46 mutation induces mitochondrial fragmentation. An additional 10 patients with optic atrophy and cerebellar atrophy, which were negative for mtDNA and OPA1 variants, were tested for pathogenic mutations in the SLC25A46 gene. However, no additional variants were identified. Our findings confirm the recent report of pathogenic SLC25A46 mutations as a novel cause for optic atrophy spectrum disorder.
Asunto(s)
Predisposición Genética a la Enfermedad/genética , Proteínas Mitocondriales/genética , Mutación , Atrofias Ópticas Hereditarias/genética , Proteínas de Transporte de Fosfato/genética , Sitios de Empalme de ARN/genética , Secuencia de Bases , Consanguinidad , Exoma/genética , Exones/genética , Salud de la Familia , Femenino , Humanos , Masculino , Padres , Linaje , Análisis de Secuencia de ADN/métodosRESUMEN
Oxidative phosphorylation disorders are often associated with increased oxidative stress and antioxidant therapy is frequently given as treatment. However, the role of oxidative stress in oxidative phosphorylation disorders or patients is far from clear and consequently the preventive or therapeutic effect of antioxidants is highly anecdotic. Therefore, we performed a systematic study of a panel of oxidative stress parameters (reactive oxygen species levels, damage and defense) in fibroblasts of twelve well-characterized oxidative phosphorylation patients with a defect in the POLG1 gene, in the mitochondrial DNA-encoded tRNA-Leu gene (m.3243A>G or m.3302A>G) and in one of the mitochondrial DNA-encoded NADH dehydrogenase complex I (CI) subunits. All except two cell lines (one POLG1 and one tRNA-Leu) showed increased reactive oxygen species levels compared with controls, but only four (two CI and two tRNA-Leu) cell lines provided evidence for increased oxidative protein damage. The absence of a correlation between reactive oxygen species levels and oxidative protein damage implies differences in damage prevention or correction. This was investigated by gene expression studies, which showed adaptive and compensating changes involving antioxidants and the unfolded protein response, especially in the POLG1 group. This study indicated that patients display individual responses and that detailed analysis of fibroblasts enables the identification of patients that potentially benefit from antioxidant therapy. Furthermore, the fibroblast model can also be used to search for and test novel, more specific antioxidants or explore ways to stimulate compensatory mechanisms.
Asunto(s)
Antioxidantes/uso terapéutico , Fibroblastos/metabolismo , Enfermedades Mitocondriales/tratamiento farmacológico , Fosforilación Oxidativa , Estrés Oxidativo , Adolescente , Adulto , Línea Celular , Niño , Preescolar , ADN Polimerasa gamma , ADN Mitocondrial/genética , ADN Polimerasa Dirigida por ADN/genética , Femenino , Humanos , Lactante , Masculino , Enfermedades Mitocondriales/metabolismo , Mutación , ARN de Transferencia de Leucina/genética , Especies Reactivas de Oxígeno/metabolismoRESUMEN
OBJECTIVE: The compound muscle action potential (CMAP) scan is a novel neurophysiological technique that appears more sensitive in detecting peripheral motor neuropathy than conventional methods. This study explores the value of the CMAP scan for the detection of subclinical diabetic peripheral motor neuropathy. METHODS: In this cross-sectional pilot study, CMAP scanning of the peroneal nerve was performed in (i) 13 well-controlled patients (8-25 yr old) with type 1 diabetes mellitus (T1DM) duration between 2.5 and 5 yr; (ii) 17 patients (10-25 yr old) with a duration of T1DM of at least 10 yr, poorly controlled and/or with microvascular complications and (iii) 13 adults with T1DM and established clinical diabetic peripheral neuropathy (DPN). Various CMAP scan variables, including measures of axonal excitability and axonal loss and reinnervation, were compared between patients and healthy controls. RESULTS: Axonal excitability was significantly decreased in the young patient groups as compared to their controls. The CMAP scan measures of axonal loss and reinnervation differed only between patients with clinical DPN and their controls. CONCLUSIONS: Motor nerve axonal excitability seems to be reduced early in T1DM, even in well-controlled young patients, and probably before (irreversible) axonal damage occurs. These changes can be measured by the CMAP scan, which makes this a promising tool for detecting nerve dysfunction in T1DM.
Asunto(s)
Potenciales de Acción , Diabetes Mellitus Tipo 1/fisiopatología , Conducción Nerviosa/fisiología , Nervio Peroneo/fisiología , Adolescente , Adulto , Axones/fisiología , Niño , Estudios Transversales , Angiopatías Diabéticas/fisiopatología , Neuropatías Diabéticas/fisiopatología , Femenino , Humanos , Masculino , Proyectos PilotoRESUMEN
BACKGROUND: Mitochondrial disorders are associated with abnormalities of the oxidative phosphorylation (OXPHOS) system and cause significant morbidity and mortality in the population. The extensive clinical and genetic heterogeneity of these disorders due to a broad variety of mutations in several hundreds of candidate genes, encoded by either the mitochondrial DNA (mtDNA) or nuclear DNA (nDNA), impedes a straightforward genetic diagnosis. A new disease gene is presented here, identified in a single Kurdish patient born from consanguineous parents with neonatally fatal Leigh syndrome and complex I deficiency. METHODS AND RESULTS: Using homozygosity mapping and subsequent positional candidate gene analysis, a total region of 255.8 Mb containing 136 possible mitochondrial genes was identified. A pathogenic mutation was found in the complex I subunit encoding the NDUFA9 gene, changing a highly conserved arginine at position 321 to proline. This is the first disease-causing mutation ever reported for NDUFA9. Complex I activity was restored in fibroblasts of the patient by lentiviral transduction with wild type but not mutant NDUFA9, confirming that the mutation causes the complex I deficiency and related disease. CONCLUSIONS: The data show that homozygosity mapping and candidate gene analysis remain an efficient way to detect mutations even in small consanguineous pedigrees with OXPHOS deficiency, especially when the enzyme deficiency in fibroblasts allows appropriate candidate gene selection and functional complementation.
Asunto(s)
Complejo I de Transporte de Electrón/genética , Enfermedad de Leigh/diagnóstico , Enfermedad de Leigh/genética , Mutación Missense , Secuencia de Aminoácidos , Células Cultivadas , Consanguinidad , Análisis Mutacional de ADN , Complejo I de Transporte de Electrón/metabolismo , Resultado Fatal , Estudios de Asociación Genética , Homocigoto , Humanos , Recién Nacido , Imagen por Resonancia Magnética , Masculino , Datos de Secuencia Molecular , NeuroimagenRESUMEN
Classic infantile Pompe disease is an inherited generalized glycogen storage disorder caused by deficiency of lysosomal acid α-glucosidase. If left untreated, patients die before one year of age. Although enzyme-replacement therapy (ERT) has significantly prolonged lifespan, it has also revealed new aspects of the disease. For up to 11 years, we investigated the frequency and consequences of facial-muscle weakness, speech disorders and dysphagia in long-term survivors. Sequential photographs were used to determine the timing and severity of facial-muscle weakness. Using standardized articulation tests and fibreoptic endoscopic evaluation of swallowing, we investigated speech and swallowing function in a subset of patients. This study included 11 patients with classic infantile Pompe disease. Median age at the start of ERT was 2.4 months (range 0.1-8.3 months), and median age at the end of the study was 4.3 years (range 7.7 months -12.2 years). All patients developed facial-muscle weakness before the age of 15 months. Speech was studied in four patients. Articulation was disordered, with hypernasal resonance and reduced speech intelligibility in all four. Swallowing function was studied in six patients, the most important findings being ineffective swallowing with residues of food (5/6), penetration or aspiration (3/6), and reduced pharyngeal and/or laryngeal sensibility (2/6). We conclude that facial-muscle weakness, speech disorders and dysphagia are common in long-term survivors receiving ERT for classic infantile Pompe disease. To improve speech and reduce the risk for aspiration, early treatment by a speech therapist and regular swallowing assessments are recommended.
Asunto(s)
Trastornos de Deglución/patología , Terapia Enzimática/métodos , Músculos Faciales/patología , Enfermedad del Almacenamiento de Glucógeno Tipo II/patología , Debilidad Muscular/patología , Trastornos del Habla/patología , Niño , Preescolar , Deglución , Trastornos de Deglución/diagnóstico , Femenino , Enfermedad del Almacenamiento de Glucógeno Tipo II/diagnóstico , Humanos , Lactante , Laringe/patología , Masculino , Debilidad Muscular/diagnóstico , Faringe/patología , Habla , Logopedia/métodosRESUMEN
AIM: Leukoencephalopathy with brainstem and spinal cord involvement and lactate elevation (LBSL) is known as a relatively mild leukoencephalopathy. We investigated the occurrence of severe variants of LBSL with extensive brain magnetic resonance imaging (MRI) abnormalities. METHOD: MRIs of approximately 3,000 patients with an unknown leukoencephalopathy were retrospectively reviewed for extensive signal abnormalities of the cerebral and cerebellar white matter, posterior limb of the internal capsule, cerebellar peduncles, pyramids, and medial lemniscus. Clinical data were retrospectively collected. RESULTS: Eleven patients fulfilled the MRI criteria (six males); six had DARS2 mutations. Clinical and laboratory findings did not distinguish between patients with and without DARS2 mutations, but MRI did. Patients with DARS2 mutations more often had involvement of structures typically affected in LBSL, including decussatio of the medial lemniscus, anterior spinocerebellar tracts, and superior and inferior cerebellar peduncles. Also, involvement of the globus pallidus was associated with DARS2 mutations. Earliest disease onset was neonatal; earliest death at 20 months. INTERPRETATION: This study confirms the occurrence of early infantile, severe LBSL, extending the known phenotypic range of LBSL. Abnormality of specific brainstem tracts and cerebellar peduncles are MRI findings that point to the correct diagnosis.
Asunto(s)
Encéfalo/patología , Leucoencefalopatías/patología , Enfermedades Mitocondriales/patología , Fibras Nerviosas Mielínicas/patología , Aspartato-ARNt Ligasa/deficiencia , Aspartato-ARNt Ligasa/genética , Niño , Preescolar , Femenino , Humanos , Lactante , Leucoencefalopatías/genética , Imagen por Resonancia Magnética , Masculino , Enfermedades Mitocondriales/genética , Mutación , Estudios Retrospectivos , Índice de Severidad de la Enfermedad , Médula Espinal/patologíaRESUMEN
Aims: This study aimed to investigate associations between renal and extrarenal manifestations of mitochondrial diseases and their natural history as well as predictors of renal disease severity and overall disease outcome. The secondary aim was to generate a protocol of presymptomatic assessment and monitoring of renal function in patients with a defined mitochondrial disease. Methods: A multicenter, retrospective cohort study was performed by the Mitochondrial Clinical and Research Network (MCRN). Patients of any age with renal manifestations associated with a genetically verified mitochondrial disease were included from 8 expert European centers specializing in mitochondrial diseases: Gothenburg, Oulu, Copenhagen, Bergen, Helsinki, Stockholm, Rotterdam, and Barcelona. Results: Of the 36 patients included, two-thirds had mitochondrial DNA-associated disease. Renal manifestations were the first sign of mitochondrial disease in 19%, and renal involvement was first identified by laboratory tests in 57% of patients. Acute kidney injury occurred in 19% of patients and was the first sign of renal disease in the majority of these. The most common renal manifestation was chronic kidney disease (75% with stage 2 or greater), followed by tubulopathy (44.4%), the latter seen mostly among patients with single large-scale mitochondrial DNA deletions. Acute kidney injury and tubulopathy correlated with worse survival outcome. The most common findings on renal imaging were increased echogenicity and renal dysplasia/hypoplasia. Renal histology revealed focal segmental glomerulosclerosis, nephrocalcinosis, and nephronophthisis. Conclusion: Acute kidney injury is a distinct renal phenotype in patients with mitochondrial disease. Our results highlight the importance to recognize renal disease as a sign of an underlying mitochondrial disease. Acute kidney injury and tubulopathy are 2 distinct indicators of poor survival in patients with mitochondrial diseases.
RESUMEN
Although mitochondrial dysfunction is the known cause of primary mitochondrial disease, mitochondrial dysfunction is often difficult to measure and prove, especially when biopsies of affected tissue are not available. In order to identify blood biomarkers of mitochondrial dysfunction, we reviewed studies that measured blood biomarkers in genetically, clinically or biochemically confirmed primary mitochondrial disease patients. In this way, we were certain that there was an underlying mitochondrial dysfunction which could validate the biomarker. We found biomarkers of three classes: 1) functional markers measured in blood cells, 2) biochemical markers of serum/plasma and 3) DNA markers. While none of the reviewed single biomarkers may perfectly reveal all underlying mitochondrial dysfunction, combining biomarkers that cover different aspects of mitochondrial impairment probably is a good strategy. This biomarker panel may assist in the diagnosis of primary mitochondrial disease patients. As mitochondrial dysfunction may also play a significant role in the pathophysiology of multifactorial disorders such as Alzheimer's disease and glaucoma, the panel may serve to assess mitochondrial dysfunction in complex multifactorial diseases as well and enable selection of patients who could benefit from therapies targeting mitochondria.
Asunto(s)
Biomarcadores/sangre , Enfermedades Mitocondriales/sangre , Enfermedades Mitocondriales/diagnóstico , Humanos , Enfermedades Mitocondriales/metabolismoRESUMEN
BACKGROUND: Leigh syndrome is an early onset, progressive, neurodegenerative disorder with developmental and motor skills regression. Characteristic magnetic resonance imaging abnormalities consist of focal bilateral lesions in the basal ganglia and/or the brainstem. The main cause is a deficiency in oxidative phosphorylation due to mutations in an mtDNA or nuclear oxidative phosphorylation gene. METHODS AND RESULTS: A consanguineous Moroccan family with Leigh syndrome comprise 11 children, three of which are affected. Marker analysis revealed a homozygous region of 11.5 Mb on chromosome 20, containing 111 genes. Eight possible mitochondrial candidate genes were sequenced. Patients were homozygous for an unclassified variant (p.P193L) in the cardiolipin synthase gene (CRLS1). As this variant was present in 20% of a Moroccan control population and enzyme activity was only reduced to 50%, this could not explain the rare clinical phenotype in our family. Patients were also homozygous for an amino acid substitution (p.L159F) in C20orf7, a new complex I assembly factor. Parents were heterozygous and unaffected sibs heterozygous or homozygous wild type. The mutation affects the predicted S-adenosylmethionine (SAM) dependent methyltransferase domain of C20orf7, possibly involved in methylation of NDUFB3 during the assembly process. Blue native gel electrophoresis showed an altered complex I assembly with only 30-40% of mature complex I present in patients and 70-90% in carriers. CONCLUSIONS: A new cause of Leigh syndrome can be a defect in early complex I assembly due to C20orf7 mutations.
Asunto(s)
Complejo I de Transporte de Electrón/metabolismo , Enfermedad de Leigh/enzimología , Enfermedad de Leigh/genética , Metiltransferasas/genética , Proteínas Mitocondriales/genética , Mutación/genética , Adolescente , Adulto , Secuencia de Aminoácidos , Sustitución de Aminoácidos/genética , Secuencia de Bases , Preescolar , Análisis Mutacional de ADN , Complejo I de Transporte de Electrón/genética , Familia , Femenino , Homocigoto , Humanos , Enfermedad de Leigh/diagnóstico por imagen , Enfermedad de Leigh/metabolismo , Leucocitos Mononucleares/enzimología , Imagen por Resonancia Magnética , Masculino , Metiltransferasas/química , Proteínas Mitocondriales/química , Datos de Secuencia Molecular , Marruecos , Linaje , Tomografía Computarizada por Rayos X , Adulto JovenRESUMEN
We report a child with a severe choreadystonic movement disorder, bilateral periventricular nodular heterotopia (BPNH), and secondary microcephaly based on compound heterozygosity for two new ARFGEF2 mutations (c.2031_2038dup and c.3798_3802del), changing the limited knowledge about the phenotype. The brain MRI shows bilateral hyperintensity of the putamen, BPNH, and generalized atrophy. Loss of ARFGEF2 function affects vesicle trafficking, proliferation/apoptosis, and neurotransmitter receptor function. This can explain BPNH and microcephaly. We hypothesize that the movement disorder and the preferential damage to the basal ganglia, specifically to the putamen, may be caused by an increased sensitivity to degeneration, a dynamic dysfunction due to neurotransmitter receptor mislocalization or a combination of both.
Asunto(s)
Movimiento Celular/fisiología , Factores de Intercambio de Guanina Nucleótido/genética , Trastornos del Movimiento/genética , Mutación , Neuronas/fisiología , Heterotopia Nodular Periventricular/genética , Anomalías Múltiples/genética , Secuencia de Bases , Encéfalo/citología , Encéfalo/patología , Niño , Análisis Mutacional de ADN , Femenino , Humanos , Masculino , Microcefalia/genética , Microcefalia/patología , Datos de Secuencia Molecular , Trastornos del Movimiento/patología , Trastornos del Movimiento/fisiopatología , Heterotopia Nodular Periventricular/patología , Heterotopia Nodular Periventricular/fisiopatología , FenotipoRESUMEN
Filamin A is an important gene involved in the development of the brain, heart, connective tissue and blood vessels. A case is presented illustrating the challenge in recognising patients with filamin A mutations. The patient, a 71-year-old woman, was known to have heart valve disease and bilateral periventricular nodular heterotopia when she died of a subarachnoid haemorrhage. Autopsy showed typical cerebral bilateral periventricular heterotopia and vascular abnormalities. Postmortally, the diagnosis of a filamin A mutation was confirmed. Recognition during life may prevent cardiovascular problems and provide possibilities for genetic counselling.
Asunto(s)
Proteínas Contráctiles/genética , Cardiopatías Congénitas/etiología , Cardiopatías Congénitas/genética , Aneurisma Intracraneal/etiología , Aneurisma Intracraneal/genética , Proteínas de Microfilamentos/genética , Mutación/genética , Mutación/fisiología , Heterotopia Nodular Periventricular/etiología , Heterotopia Nodular Periventricular/genética , Anciano , Encéfalo/patología , Angiografía Cerebral , ADN/genética , Exones/genética , Resultado Fatal , Femenino , Filaminas , Cardiopatías Congénitas/patología , Humanos , Aneurisma Intracraneal/patología , Angiografía por Resonancia Magnética , Heterotopia Nodular Periventricular/patología , Tomografía Computarizada por Rayos XRESUMEN
BACKGROUND: The m.3243A>G mutation in the mitochondrial tRNA(Leu(UUR)) gene is an example of a mutation causing a very heterogeneous phenotype. It is the most frequent cause (80%) of the MELAS syndrome (mitochondrial myopathy, encephalopathy, lactic acidosis and stroke-like episodes), but it can also lead in addition or separately to type 2 diabetes, deafness, renal tubulopathy and/or cardiomyopathy. METHODS: To identify pathogenic processes induced by this mutation, we compared global gene expression levels of muscle biopsies from affected and unaffected mutation carriers with controls. RESULTS AND CONCLUSIONS: Gene expression changes were relatively subtle. In the asymptomatic group 200 transcripts were upregulated and 12 were downregulated, whereas in the symptomatic group 15 transcripts were upregulated and 52 were downregulated. In the asymptomatic group, oxidative phosphorylation (OXPHOS) complex I and IV genes were induced. Protein turnover and apoptosis were elevated, most likely due to the formation of dysfunctional and reactive oxygen species (ROS) damaged proteins. These processes returned to normal in symptomatic patients. Components of the complement system were upregulated in both groups, but the strongest in the symptomatic group, which might indicate muscle regeneration--most likely, protein damage and OXPHOS dysfunction stimulate repair (protein regeneration) and metabolic adaptation (OXPHOS). In asymptomatic individuals these processes suffice to prevent the occurrence of symptoms. However, in affected individuals the repair process terminates, presumably because of excessive damage, and switches to muscle regeneration, as indicated by a stronger complement activation. This switch leaves increasingly damaged tissue in place and muscle pathology becomes manifest. Therefore, the expression of complement components might be a marker for the severity and progression of MELAS clinical course.
Asunto(s)
Síndrome MELAS/genética , Mutación Puntual , ARN de Transferencia de Leucina/genética , Adolescente , Adulto , Anciano , Apoptosis , Niño , Preescolar , Activación de Complemento , Femenino , Perfilación de la Expresión Génica , Heterocigoto , Humanos , Síndrome MELAS/fisiopatología , Masculino , Persona de Mediana Edad , Músculo Esquelético/fisiopatología , Fosforilación Oxidativa , Proteínas/metabolismo , ARN de Transferencia de Leucina/metabolismoRESUMEN
Early onset cerebellar Ataxia (EOAc) comprises a large group of rare heterogeneous disorders. Determination of the underlying etiology can be difficult given the broad differential diagnosis and the complexity of the genotype-phenotype relationships. This may change the diagnostic work-up into a time-consuming, costly and not always rewarding task. In this overview, the Childhood Ataxia and Cerebellar Group of the European Pediatric Neurology Society (CACG-EPNS) presents a diagnostic algorithm for EOAc patients. In seven consecutive steps, the algorithm leads the clinician through the diagnostic process, including EOA identification, application of the Inventory of Non-Ataxic Signs (INAS), consideration of the family history, neuro-imaging, laboratory investigations, genetic testing by array CGH and Next Generation Sequencing (NGS). In children with EOAc, this algorithm is intended to contribute to the diagnostic process and to allow uniform data entry in EOAc databases.
Asunto(s)
Algoritmos , Sistemas de Apoyo a Decisiones Clínicas , Degeneraciones Espinocerebelosas/diagnóstico , Adolescente , Niño , Diagnóstico Diferencial , Femenino , Humanos , MasculinoRESUMEN
BACKGROUND: Detection of mutations in the mitochondrial DNA (mtDNA) is usually limited to common mutations and the transfer RNA genes. However, mutations in other mtDNA regions can be an important cause of oxidative phosphorylation (OXPHOS) disease as well. OBJECTIVE: To investigate whether regions in the mtDNA are preferentially mutated in patients with OXPHOS disease. METHODS: Screening of the mtDNA for heteroplasmic mutations was performed by denaturing high-performance liquid chromatography analysis of 116 patients with OXPHOS disease but without the common mtDNA mutations. RESULTS: An mtDNA sequence variant was detected in 15 patients, 5 of which were present in the ND5 gene. One sequence variant was new and three were known, one of which was found twice. The novel sequence variant m.13511A-->T occurred in a patient with a Leigh-like syndrome. The known mutation m.13513G-->A, associated with mitochondrial encephalomyopathy lactic acidosis and stroke-like syndrome (MELAS) and MELAS/Leigh/Leber hereditary optic neuropathy overlap syndrome, was found in a relatively low percentage in two patients from two different families, one with a MELAS/Leigh phenotype and one with a MELAS/chronic progressive external ophthalmoplegia phenotype. The known mutation m.13042G-->A, detected previously in a patient with a MELAS/myoclonic epilepsy, ragged red fibres phenotype and in a family with a prevalent ocular phenotype, was now found in a patient with a Leigh-like phenotype. The sequence variant m.12622G-->A was reported once in a control database as a polymorphism, but is reported in this paper as heteroplasmic in three brothers, all with infantile encephalopathy (Leigh syndrome) fatal within the first 15 days of life. Therefore, a causal relationship between the presence of this sequence variant and the onset of mitochondrial disease cannot be entirely excluded at this moment. CONCLUSIONS: Mutation screening of the ND5 gene is advised for routine diagnostics of patients with OXPHOS disease, especially for those with MELAS- and Leigh-like syndrome with a complex I deficiency.
Asunto(s)
Complejo I de Transporte de Electrón/genética , Enfermedades Mitocondriales/genética , Proteínas Mitocondriales/genética , Fosforilación Oxidativa , Secuencia de Aminoácidos , Animales , Encéfalo/anomalías , Niño , Cromatografía Líquida de Alta Presión , Análisis Mutacional de ADN , ADN Mitocondrial/genética , Enfermedades en Gemelos , Complejo I de Transporte de Electrón/química , Complejo I de Transporte de Electrón/deficiencia , Complejo I de Transporte de Electrón/fisiología , Resultado Fatal , Femenino , Pruebas Genéticas , Humanos , Interacciones Hidrofóbicas e Hidrofílicas , Recién Nacido , Enfermedad de Leigh/genética , Síndrome MELAS/genética , Masculino , Mitocondrias Musculares/enzimología , Proteínas Mitocondriales/química , Proteínas Mitocondriales/deficiencia , Proteínas Mitocondriales/fisiología , Datos de Secuencia Molecular , Mutación Missense , Fenotipo , Subunidades de Proteína , Alineación de Secuencia , Homología de Secuencia de AminoácidoRESUMEN
PURPOSE: Leber hereditary optic neuropathy (LHON) is recognized as the most common cause of isolated blindness in young men. The current study was designed to test whether LHON as a mitochondrial disease is associated with vascular functional alterations characterized by aortic elastic properties during echocardiography. METHODS: A total of 19 patients with typical features of LHON aged 42+/-13 years (10 males) were included. Their results were compared to 19 age- and gender-matched healthy controls. Aortic stiffness index was calculated from the echocardiographically derived aortic diameters and the clinical blood pressure data. RESULTS: In this patient population, the point mutation was present in 3460G>A position in five cases, in 11778G>A position in five cases, and in 14484T>C position in nine patients. Diastolic aortic diameter (26.0+/-2.5 mm vs 28.4+/-4.1 mm, p<0.05) and aortic stiffness index (5.1+/-2.6 vs 12.0+/-7.9, p<0.05) were significantly increased in LHON patients compared to controls. CONCLUSIONS: Aortic stiffness can be increased in LHON disease, but further studies are warranted to confirm these findings in a larger LHON patient population with a more reliable method focusing on the pathophysiologic background.
Asunto(s)
Aorta/fisiopatología , Atrofia Óptica Hereditaria de Leber/fisiopatología , Adulto , Velocidad del Flujo Sanguíneo , Presión Sanguínea , ADN Mitocondrial/genética , Ecocardiografía , Elasticidad , Femenino , Humanos , Masculino , Atrofia Óptica Hereditaria de Leber/genética , Mutación Puntual , Estudios Prospectivos , Ultrasonografía DopplerRESUMEN
Complex I activity of the mitochondrial respiratory chain is difficult to measure in blood lymphocytes because of the limited access of substrates to the enzyme complex in these cells. The results of the present study show that permeabilization of human blood lymphocytes in the presence of protease inhibitors by three cycles of freeze-thawing enables reproducible detection of the rotenone-sensitive complex I activity. To that end, the water-soluble coenzyme Q(10) analogue CoQ(1) and a relatively high concentration of blood lymphocytes were combined in small quartz cuvettes so that the amount of blood needed for this assay remained low. The relationship between the initial rate of NADH oxidation by complex I and the protein concentration was quasi-linear. The fractional inhibition of the total NADH:CoQ(1) oxidoreductase by a saturating concentration of rotenone decreased sharply at CoQ(1) concentrations higher than 20 muM, which is indicative, but does not prove the involvement of a second CoQ(1) binding site at complex I. Since the present complex I assay requires only a small amount of blood, the functionality of this important respiratory chain complex can be assessed in an easy and reliable manner not only in adult patients but also in children suspected to have a mitochondrial disease.
Asunto(s)
Complejo I de Transporte de Electrón/metabolismo , Linfocitos/enzimología , Proteínas Mitocondriales/metabolismo , Adulto , Niño , Complejo I de Transporte de Electrón/sangre , Humanos , Cinética , Mitocondrias/enzimología , NAD/metabolismo , Oxidación-Reducción , Ubiquinona/metabolismoRESUMEN
Several mutations in nuclear genes encoding for mitochondrial components have been associated with an increased cancer risk or are even causative, e.g. succinate dehydrogenase (SDHB, SDHC and SDHD genes) and iso-citrate dehydrogenase (IDH1 and IDH2 genes). Recently, studies have suggested an eminent role for mitochondrial DNA (mtDNA) mutations in the development of a wide variety of cancers. Various studies associated mtDNA abnormalities, including mutations, deletions, inversions and copy number alterations, with mitochondrial dysfunction. This might, explain the hampered cellular bioenergetics in many cancer cell types. Germline (e.g. m.10398A>G; m.6253T>C) and somatic mtDNA mutations as well as differences in mtDNA copy number seem to be associated with cancer risk. It seems that mtDNA can contribute as driver or as complementary gene mutation according to the multiple-hit model. This can enhance the mutagenic/clonogenic potential of the cell as observed for m.8993T>G or influences the metastatic potential in later stages of cancer progression. Alternatively, other mtDNA variations will be innocent passenger mutations in a tumor and therefore do not contribute to the tumorigenic or metastatic potential. In this review, we discuss how reported mtDNA variations interfere with cancer treatment and what implications this has on current successful pharmaceutical interventions. Mutations in MT-ND4 and mtDNA depletion have been reported to be involved in cisplatin resistance. Pharmaceutical impairment of OXPHOS by metformin can increase the efficiency of radiotherapy. To study mitochondrial dysfunction in cancer, different cellular models (like ρ(0) cells or cybrids), in vivo murine models (xenografts and specific mtDNA mouse models in combination with a spontaneous cancer mouse model) and small animal models (e.g. Danio rerio) could be potentially interesting to use. For future research, we foresee that unraveling mtDNA variations can contribute to personalized therapy for specific cancer types and improve the outcome of the disease.
Asunto(s)
ADN Mitocondrial/genética , Neoplasias/genética , Neoplasias/terapia , Animales , Resistencia a Antineoplásicos , Humanos , Mitocondrias/genética , Proteínas Mitocondriales/genética , Mutación , Medicina de Precisión , Tolerancia a RadiaciónRESUMEN
Numerous studies have described the poor visuo-spatial processing capacities of subjects with Williams-Beuren syndrome (WBS), a genetically based developmental disorder. Since visual perception and eye movements are closely related we hypothesized that the poor visuo-spatial processing capacities of subjects with WBS might be related to a poor saccadic control. Thereto, we recorded horizontal and vertical saccadic eye movements to targets using infrared video-oculography in 27 subjects with WBS and eight healthy controls. In the WBS group saccadic gains were highly variable, both between and within individual subjects, and they often needed more than one correction saccade to reach the target. Ten (out of a subgroup of 22) WBS subjects showed a large number of hypometric and/or hypermetric saccades, and, also a left-right asymmetry in saccadic gains was observed in WBS. We conclude that the observed impairments in saccadic control are likely to affect the proper processing of visuo-spatial information.