NERVE-DEPENDENT INDUCTION OF ACHR EPSILON-SUBUNIT GENE-EXPRESSION IN MUSCLE IS INDEPENDENT OF STATE OF DIFFERENTIATION

To determine if the expression of the epsilon-subunit of the acetylcho line receptor by the subsynaptic nuclei in skeletal muscle is dependen t on the state of differentiation of the muscle, we have compared the spatiotemporal distribution of epsilon-subunit transcripts during syna pse formation in fetal and adult muscle. Both during ''ontogenic'' syn aptogenesis in the fetus and during ''ectopic'' synaptogenesis in the adult animal the motor nerve induced focally the expression of the eps ilon-subunit mRNA in subsynaptic nuclei. The temporal expression patte rns at both types of developing synapses were similar. The results sup port the view that in muscle developing in vivo epsilon-subunit gene t ranscription and its stabilization in subsynaptic nuclei is exclusivel y controlled by the motor neuron, independently of the developmental s tate of the muscle nuclei. Thus, both nerve and muscle remain plastic in their respective abilities to induce and express the synapse-specif ic combination of AChR subunit genes. (C) 1994 Academic Press, Inc.