Induction of adult-type nicotinic acetylcholine receptor gene expression in noninnervated regenerating muscle.

Expression of adult-type nicotinic acetylcholine receptors at the neuromuscular junction is thought to result from selective induction of their genes in endplate-associated nuclei due to local neurotrophic control. However, denervation studies indicate that endplate-specific expression can be maintained in the absence of the nerve. We investigated the role played by the basal lamina in this expression by assaying for the adult-type-specific epsilon RNA in noninnervated regenerating muscle. We found that this RNA is locally expressed beneath the old endplates after 10 days of regeneration. At earlier times epsilon RNA is also found in areas other than the endplate region. These results indicate that in adult muscle the basal lamina contains all the components necessary to direct nicotinic acetylcholine receptor gene expression to the endplate.