Fig. 5

Alternative splicing of genes involved in excitation-contraction coupling. Acetylcholine secreted from the synaptic nerve ends binds to acetylcholine receptors and generates an action potential that transmits through T-tubule, activating ryanodine receptors to efflux Ca²⁺ from sarcoplasmic reticulum and SERCA channels facilitate influx of Ca²⁺. Ryanodine receptor and SERCA channel transcripts undergo “fetal-to-adult” temporal shift in alternative splicing at exons 29 and 33 and exon 22, respectively. Fetal splice variants of RyR1 and SERCA (also observed in DM pathogenesis) are less efficient in ATPase and Ca²⁺ handling