Targeting transcription to the neuromuscular synapse

Concomitant with innervation, genes coding for components of the neuromuscu lar junction become exclusively expressed in subsynaptic nuclei. A six-base pair element, the N box, can confer synapse-specific transcription to the acetylcholine nicotinic receptor delta and epsilon subunit, utrophin, and a cetylcholine esterase genes. N box-dependent synaptic expression is stimula ted by the nerve-derived signal agrin and the trophic factor neuregulin, wh ich triggers the MAPK and JNK signaling pathways, to ultimately allow activ ation by the N box binding Ets transcription factor GABP.