G.P.10.10 Dysferlin does not play an essential role in skeletal myoblast fusion

Abstract

Mutations in the dysferlin gene cause limb-girdle muscular dystrophy type 2B, Miyoshi myopathy and distal anterior compartment myopathy, collectively known as dysferlinopathy. The dysferlin protein containing six C2 domains and one transmembrane domain has been implicated in the membrane resealing step of sarcolemma repair and myoblast fusion. However, the mechanism of the disease and the function of dysferlin in this process are still largely unknown. To investigate the function of dysferlin in myoblast differentiation, primary cultures and skeletal muscle tissue from wild type C57BL10, dysferlin-deficient C57BL10.SJL-dysf and dystrophin-deficient mdx mice were analysed for growth and fusion as well as protein expression during differentiation. The primary myoblasts generated from C57BL10.SJL-dysf have a similar division rate and fusion index compared to C57BL10 and mdx mice. In C57BL10 and mdx, dysferlin is expressed at the sites of membrane fusion and cell membrane after differentiation. No significant difference was found in myogenin expression in C57BL10.SJL-dysf myoculture compared to C57BL10 and mdx myoculture. We observed 20–30% of wild type levels of the dysferlin protein in C57BL10.SJL-dysf neonatal muscle tissue and primary myoblasts generated from neonatal mice by Western blot. However, the truncated dysferlin protein in C57BL10.SJL-dysf fails to correctly localise at the sites of membrane fusion and cell membrane in primary culture and skeletal muscle indicating that it is not functional. The lack of functional dysferlin and the same differentiation efficiency in C57BL10.SJL-dysf suggests that dysferlin does not play an essential role in myoblast fusion.