Novel role for prepatterned nicotinic acetylcholine receptors during myogenesis

Introduction: Before the nerve contacts the skeletal muscle, the nicotinic acetylcholine receptors (nAChRs) form aggregates named prepatterned cluster. We investigated their role in the occurrence of Ca2+ spikes and twitching during myogenesis. Methods: Cultured mouse myotubes were used as cell model. Cells were subjected to a combination of immunostaining, Ca2+ imaging and electrophysiological analysis. Results: A single prepatterned nAChR cluster per myotube was generally detected. A correlation between formation of the prepatterned clusters and occurrence of Ca2+ spikes and twitching was observed. Increase in size of the prepatterned clusters raised the frequency of Ca2+ spikes and twitching. Blockade of the electrical activity triggered by the autocrine activation of prepatterned nAChR induced over-numbered nAChR clusters. Conclusions: Prepatterned nAChR aggregation is requisite for Ca2+ spikes and twitching of developing myotubes. Moreover, prepatterned nAChR-driven electrical activity preserves the distribution of nAChRs, mimicking the effect of synaptic activity before innervation.