Transient expression of the intermediate filament nestin during skeletal muscle development

Abstract

It has previously been established that skeletal muscle development is accompanied by changes in the compo-sition of intermediate filaments: vimentin is expressed predominantly in myoblasts and desmin in adult myotubes. We show that the intermediate filament tran-sitions during muscle development are more complex, and involve a transient expression of the recently dis-covered intermediate filament nestin. Nestin RNA is expressed predominantly early, in a biphasic pattern, and is markedly downregulated in adult rat muscle, whereas desmin RNA becomes more abundant through-out development. Nestin protein was found up to the postnatal myotube stage, where it colocalized with desmin in Z bands. The intracellular distribution of nestin, vimentin and desmin was analysed in the human myogenic cell line G6 before and after in vitro differ-entiation. Despite its more distant evolutionary and structural relationship to the other two intermediate fil-aments, nestin formed a cytoplasmic filamentous net-work indistinguishable from that of desmin and vimentin, both in undifferentiated myoblasts and after differentiation to multinuclear myotubes. In conclusion, our data suggest that nestin is an integrated component of the dynamic intermediate filament network during muscle development and that nestin copolymerizes with desmin and vimentin at stages of coexpression.