During neuromuscular development, the nerve induces the expression of acetylcholine receptor (AChR) epsilon-subunit gene selectively in synaptic myonuclei. Here we show that even after elimination of neural effects by denervation, synaptic expression of epsilon-subunit transcripts is maintained for > 4 months. In contrast, after damage of the extracellular matrix (ECM) by treatment with proteolytic enzymes, epsilon-subunit mRNA is significantly reduced within less than 1 day, indicating a role of ECM in the regulation of AChR subunit transcripts at the synapse.