RESUMO
Centronuclear myopathy (CNM) is a genetically heterogeneous disorder associated with general skeletal muscle weakness, type I fiber predominance and atrophy, and abnormally centralized nuclei. Autosomal dominant CNM is due to mutations in the large GTPase dynamin 2 (DNM2), a mechanochemical enzyme regulating cytoskeleton and membrane trafficking in cells. To date, 40 families with CNM-related DNM2 mutations have been described, and here we report 60 additional families encompassing a broad genotypic and phenotypic spectrum. In total, 18 different mutations are reported in 100 families and our cohort harbors nine known and four new mutations, including the first splice-site mutation. Genotype-phenotype correlation hypotheses are drawn from the published and new data, and allow an efficient screening strategy for molecular diagnosis. In addition to CNM, dissimilar DNM2 mutations are associated with Charcot-Marie-Tooth (CMT) peripheral neuropathy (CMTD1B and CMT2M), suggesting a tissue-specific impact of the mutations. In this study, we discuss the possible clinical overlap of CNM and CMT, and the biological significance of the respective mutations based on the known functions of dynamin 2 and its protein structure. Defects in membrane trafficking due to DNM2 mutations potentially represent a common pathological mechanism in CNM and CMT.
Assuntos
Dinamina II/genética , Genes Dominantes , Estudos de Associação Genética , Mutação , Miopatias Congênitas Estruturais/genética , Sequência de Aminoácidos , Dinamina II/química , Humanos , Dados de Sequência Molecular , Miopatias Congênitas Estruturais/diagnóstico , Polimorfismo Genético , Alinhamento de SequênciaRESUMO
In 2004, Anderson et al. reported a homozygous 2502 bp deletion including exon 55 of the nebulin gene in five Ashkenazi Jewish probands with nemaline myopathy. We determined the occurrence of this deletion in a world-wide series of 355 nemaline myopathy probands with no previously known mutation in other genes and found the mutation in 14 probands, two of whom represented families previously ascertained by Anderson et al. Two of the families were not of known Ashkenazi Jewish descent but they had the haplotype known to segregate with this mutation. In all but two of eight homozygous patients, the clinical picture was more severe than in typical nemaline myopathy.
Assuntos
Éxons/genética , Efeito Fundador , Predisposição Genética para Doença/genética , Proteínas Musculares/genética , Mutação/genética , Miopatias da Nemalina/genética , Análise Mutacional de DNA , Feminino , Deleção de Genes , Predisposição Genética para Doença/etnologia , Testes Genéticos , Saúde Global , Haplótipos , Homozigoto , Humanos , Padrões de Herança/genética , Judeus/etnologia , Judeus/genética , Masculino , Miopatias da Nemalina/etnologiaRESUMO
Nemaline myopathy (NM) is a congenital myopathy characterized by muscle weakness and nemaline bodies in affected myofibers. Five NM genes, all encoding components of the sarcomeric thin filament, are known. We report identification of a sixth gene, CFL2, encoding the actin-binding protein muscle cofilin-2, which is mutated in two siblings with congenital myopathy. The proband's muscle contained characteristic nemaline bodies, as well as occasional fibers with minicores, concentric laminated bodies, and areas of F-actin accumulation. Her affected sister's muscle was reported to exhibit nonspecific myopathic changes. Cofilin-2 levels were significantly lower in the proband's muscle, and the mutant protein was less soluble when expressed in Escherichia coli, suggesting that deficiency of cofilin-2 may result in reduced depolymerization of actin filaments, causing their accumulation in nemaline bodies, minicores, and, possibly, concentric laminated bodies.