RESUMO
BACKGROUND: Beckwith-Wiedemann syndrome (BWS) is a cancer predisposition syndrome caused by defects on chromosome 11p15.5. The quantitative cancer risks in BWS patients depend on the underlying (epi)genotype but have not yet been assessed in a population-based manner. METHODS: We identified a group of 321 individuals with a molecularly confirmed diagnosis of BWS and analysed the cancer incidence up to age 15 years and cancer spectrum by matching their data with the German Childhood Cancer Registry. RESULTS: We observed 13 cases of cancer in the entire BWS cohort vs 0.4 expected. This corresponds to a 33-fold increased risk (standardised incidence ratio (SIR) = 32.6; 95% confidence interval = 17.3-55.7). The specific cancers included hepatoblastoma (n = 6); nephroblastoma (n = 4); astrocytoma (n = 1); neuroblastoma (n = 1) and adrenocortical carcinoma (n = 1). The cancer SIR was highest in patients with a paternal uniparental disomy of 11p15.5 (UPDpat). A high cancer risk remained when cases of cancer diagnosed prior to the BWS diagnosis were excluded. CONCLUSIONS: This study confirms an increased cancer risk in children with BWS. Our findings suggest that the highest cancer risk is associated with UPDpat. We were unable to confirm an excessive cancer risk in patients with IC1 gain of methylation (IC1-GOM) and this finding requires further investigation.
Assuntos
Síndrome de Beckwith-Wiedemann/genética , Cromossomos Humanos Par 11/genética , Neoplasias/epidemiologia , Dissomia Uniparental/genética , Adolescente , Síndrome de Beckwith-Wiedemann/epidemiologia , Criança , Pré-Escolar , Feminino , Alemanha/epidemiologia , Humanos , Incidência , Lactente , Masculino , Neoplasias/classificação , Sistema de Registros , Estudos RetrospectivosRESUMO
Deletions in mitochondrial DNA (mtDNA) are an important cause of human disease and their accumulation has been implicated in the ageing process. As mtDNA is a high copy number genome, the coexistence of deleted and wild-type mtDNA molecules within a single cell defines heteroplasmy. When deleted mtDNA molecules, driven by intracellular clonal expansion, reach a sufficiently high level, a biochemical defect emerges, contributing to the appearance and progression of clinical pathology. Consequently, it is relevant to determine the heteroplasmy levels within individual cells to understand the mechanism of clonal expansion. Heteroplasmy is reflected in a mosaic distribution of cytochrome c oxidase (COX)-deficient muscle fibers. We applied droplet digital PCR (ddPCR) to single muscle fibers collected by laser-capture microdissection (LCM) from muscle biopsies of patients with different paradigms of mitochondrial disease, characterized by the accumulation of single or multiple mtDNA deletions. By combining these two sensitive approaches, ddPCR and LCM, we document different models of clonal expansion in patients with single and multiple mtDNA deletions, implicating different mechanisms and time points for the development of COX deficiency in these molecularly distinct mitochondrial cytopathies.
Assuntos
DNA Mitocondrial/genética , Células Musculares/metabolismo , Reação em Cadeia da Polimerase/métodos , Deleção de Sequência/genética , Adolescente , Adulto , Idoso , Biópsia , Complexo IV da Cadeia de Transporte de Elétrons/metabolismo , Feminino , GTP Fosfo-Hidrolases/genética , Dosagem de Genes , Genes Recessivos , Humanos , Masculino , Pessoa de Meia-Idade , Fibras Musculares Esqueléticas/metabolismo , Mutação/genética , Fosforilação Oxidativa , Reprodutibilidade dos Testes , Succinato Desidrogenase/metabolismo , Adulto JovemRESUMO
Mitochondrial dynamics play an important role in cellular homeostasis and a variety of human diseases are linked to its dysregulated function. Here, we describe a 15-year-old boy with a novel disease caused by altered mitochondrial dynamics. The patient was the second child of consanguineous Jewish parents. He developed progressive muscle weakness and exercise intolerance at 6 years of age. His muscle biopsy revealed mitochondrial myopathy with numerous ragged red and cytochrome c oxidase (COX) negative fibers and combined respiratory chain complex I and IV deficiency. MtDNA copy number was elevated and no deletions of the mtDNA were detected in muscle DNA. Whole exome sequencing identified a homozygous nonsense mutation (p.Q92*) in the MIEF2 gene encoding the mitochondrial dynamics protein of 49 kDa (MID49). Immunoblotting revealed increased levels of proteins promoting mitochondrial fusion (MFN2, OPA1) and decreased levels of the fission protein DRP1. Fibroblasts of the patient showed elongated mitochondria, and significantly higher frequency of fusion events, mtDNA abundance and aberrant mitochondrial cristae ultrastructure, compared with controls. Thus, our data suggest that mutations in MIEF2 result in imbalanced mitochondrial dynamics and a combined respiratory chain enzyme defect in skeletal muscle, leading to mitochondrial myopathy.
Assuntos
Fibroblastos/metabolismo , Dinâmica Mitocondrial/genética , Proteínas Mitocondriais , Doenças Musculares , Mutação de Sentido Incorreto , Fatores de Alongamento de Peptídeos , Complexo I de Transporte de Elétrons/genética , Complexo I de Transporte de Elétrons/metabolismo , Complexo IV da Cadeia de Transporte de Elétrons/genética , Complexo IV da Cadeia de Transporte de Elétrons/metabolismo , Feminino , Fibroblastos/patologia , GTP Fosfo-Hidrolases/genética , GTP Fosfo-Hidrolases/metabolismo , Humanos , Masculino , Proteínas Mitocondriais/genética , Proteínas Mitocondriais/metabolismo , Doenças Musculares/genética , Doenças Musculares/metabolismo , Doenças Musculares/patologia , Fatores de Alongamento de Peptídeos/genética , Fatores de Alongamento de Peptídeos/metabolismo , Cultura Primária de CélulasRESUMO
PurposeDiagnosing primary mitochondrial diseases (MDs) is challenging in clinical practice. The mitochondrial disease criteria (MDC) have been developed to quantify the clinical picture and evaluate the probability of an underlying MD and the need for a muscle biopsy. In this new genetic era with next-generation sequencing in routine practice, we aim to validate the diagnostic value of MDC.MethodsWe retrospectively studied MDC in a multicenter cohort of genetically confirmed primary MD patients.ResultsWe studied 136 patients (61 male, 91 nuclear DNA (nDNA) mutations). Forty-five patients (33%) had probable MD and 69 (51%) had definite MD according to the MDC. A muscle biopsy was performed in 63 patients (47%). Patients with nDNA mutations versus mitochondrial DNA mutations were younger (6.4 ± 9.7 versus 19.5 ± 17.3 y) and had higher MDC (7.07 ± 1.12/8 versus 5.69 ± 1.94/8). At a cutoff of 6.5/8, the sensitivity to diagnose patients with nDNA mutations is 72.5% with a positive predictive value of 69.5%. In the nDNA mutation group, whole-exome sequencing could diagnose patients with lower scores (MDC (6.84 ± 1.51/8) compared to Sanger sequencing MDC (7.44 ± 1.13/8, P = 0.025)). Moreover 7/8 patients diagnosed with possible MD by MDC were diagnosed by whole-exome sequencing.ConclusionMDC remain very useful in the clinical diagnosis of MD, in interpreting whole-exome results and deciding on the need for performing muscle biopsy.
Assuntos
Genoma Mitocondrial , Genômica , Mitocôndrias/genética , Doenças Mitocondriais/diagnóstico , Doenças Mitocondriais/genética , Adolescente , Adulto , Idoso , Criança , Pré-Escolar , Feminino , Genes Mitocondriais , Estudos de Associação Genética , Predisposição Genética para Doença , Testes Genéticos/métodos , Genômica/métodos , Humanos , Lactente , Recém-Nascido , Masculino , Pessoa de Meia-Idade , Mitocôndrias/metabolismo , Mutação , Estudos Retrospectivos , Fluxo de Trabalho , Adulto JovemRESUMO
Liver failure is a heterogeneous condition which may be fatal and the primary cause is frequently unknown. We investigated mitochondrial oxidative phosphorylation in patients undergoing liver transplantation. We studied 45 patients who had liver transplantation due to a variety of clinical presentations. Blue native polyacrylamide gel electrophoresis with immunodetection of respiratory chain complexes I-V, biochemical activity of respiratory chain complexes II and IV and quantification of mitochondrial DNA (mtDNA) copy number were investigated in liver tissue collected from the explanted liver during transplantation. Abnormal mitochondrial function was frequently present in this cohort: ten of 40 patients (25 %) had a defect of one or more respiratory chain enzyme complexes on blue native gels, 20 patients (44 %) had low activity of complex II and/or IV and ten (22 %) had a reduced mtDNA copy number. Combined respiratory chain deficiency and reduced numbers of mitochondria were detected in all three patients with acute liver failure. Low complex IV activity in biliary atresia and complex II defects in cirrhosis were common findings. All six patients diagnosed with liver tumours showed variable alterations in mitochondrial function, probably due to the heterogeneity of the presenting tumour. In conclusion, mitochondrial dysfunction is common in severe liver failure in non-mitochondrial conditions. Therefore, in contrast to the common practice detection of respiratory chain abnormalities in liver should not restrict the inclusion of patients for liver transplantation. Furthermore, improving mitochondrial function may be targeted as part of a complex therapy approach in different forms of liver diseases.
Assuntos
Falência Hepática/patologia , Fígado/patologia , Mitocôndrias/patologia , Doenças Mitocondriais/patologia , Adolescente , Adulto , Atresia Biliar/metabolismo , Atresia Biliar/patologia , Criança , Pré-Escolar , DNA Mitocondrial/metabolismo , Transporte de Elétrons/fisiologia , Complexo IV da Cadeia de Transporte de Elétrons/metabolismo , Feminino , Humanos , Lactente , Fígado/metabolismo , Cirrose Hepática/metabolismo , Cirrose Hepática/patologia , Falência Hepática/metabolismo , Neoplasias Hepáticas/metabolismo , Neoplasias Hepáticas/patologia , Transplante de Fígado/métodos , Masculino , Pessoa de Meia-Idade , Mitocôndrias/metabolismo , Doenças Mitocondriais/metabolismo , Fosforilação Oxidativa , Adulto JovemRESUMO
INTRODUCTION: Neurogenic muscle weakness, ataxia, and retinitis pigmentosa (NARP) is caused by m.8993T>G/C mutations in the mitochondrial adenosine triphosphate synthase subunit 6 gene (MT-ATP6). Traditionally, heteroplasmy levels between 70% and 90% lead to NARP, and >90% result in Leigh syndrome. METHODS: In this study we report a 30-year-old man with NARP and m.8993T>G in MT-ATP6. RESULTS: Although the patient carried the mutation in homoplasmic state in blood with similarly high levels in urine (94%) and buccal swab (92%), he presented with NARP and not the expected, more severe Leigh phenotype. The mutation could not be detected in any of the 3 analyzed tissues of the mother, indicating a large genetic shift between mother and offspring. Nerve biopsy revealed peculiar endoneurial Schwann cell nuclear accumulations, clusters of concentrically arranged Schwann cells devoid of myelinated axons, and degenerated mitochondria. CONCLUSIONS: We emphasize the phenotypic variability of the m.8993T>G MT-ATP6 mutation and the need for caution in predictive counseling in such patients. Muscle Nerve 54: 328-333, 2016.