RYR1 and myotonic dystrophy type 1: In addition, fetal variants of ryanodine receptor type 1 (RyR1), which is involved in the calcium release from intracellular organelles, and SERCA1, which is responsible for calcium transport from the cytosol into the sarcoplasmic reticulum, are significantly increased in skeletal muscles from DM1 patients and in HSALR mouse [30,31].