RESUMO
Myosin heavy chain (MyHC) is the major contractile protein of muscle. We report the first complete cosmid cloning and definitive physical map of the tandemly linked human skeletal MyHC genes at 17p13.1. The map provides new information on the order, size, and relative spacing of the genes. and it resolves uncertainties about the two fastest twitch isoforms. The physical order of the genes is demonstrated to contrast with the temporal order of their developmental expression. Furthermore, nucleotide sequence comparisons allow an approximation of the relative timing of five ancestral duplications that created distinct genes for the six isoforms. A firm foundation is provided for molecular analysis in patients with suspected primary skeletal myosinopathies and for detailed modelling of the hypervariable surface loops which dictate myosin's kinetic properties.
Assuntos
Músculo Esquelético/embriologia , Cadeias Pesadas de Miosina/genética , Regiões 3' não Traduzidas , Sequência de Aminoácidos , Sequência de Bases , Mapeamento Cromossômico , Clonagem Molecular , Cosmídeos , Éxons , Humanos , Dados de Sequência Molecular , Desenvolvimento Muscular , Músculo Esquelético/crescimento & desenvolvimento , Doenças Musculares/genética , Músculos Oculomotores/embriologia , Músculos Oculomotores/crescimento & desenvolvimento , Isoformas de Proteínas/genética , Sarcômeros/química , Alinhamento de SequênciaRESUMO
Limb-girdle muscular dystrophies 2C-F represent a family of autosomal recessive diseases caused by defects in sarcoglycan genes. The cardiomyopathic hamster is a naturally occurring model for limb-girdle muscular dystrophy caused by a primary deficiency in delta-sarcoglycan. We show here that acute sarcolemmal disruption occurs in this animal model during forceful muscle contraction. A recombinant adeno-associated virus vector encoding human delta-sarcoglycan conferred efficient and stable genetic reconstitution in the adult cardiomyopathic hamster when injected directly into muscle. A quantitative assay demonstrated that vector-transduced muscle fibers are stably protected from sarcolemmal disruption; there was no associated inflammation or immunologic response to the vector-encoded protein. Efficient gene transduction with rescue of the sarcoglycan complex in muscle fibers of the distal hindlimb was also obtained after infusion of recombinant adeno-associated virus into the femoral artery in conjunction with histamine-induced endothelial permeabilization. This study provides a strong rationale for the development of gene therapy for limb-girdle muscular dystrophy.
