The combined effect of increased ECC activity coupled with myotonia, due to mis-splicing of a chloride channel [4,26], and altered Ca2+ homeostasis (RyR1 and SERCA1 mis-splicing) may lead to a chronic Ca2+ overload already observed in DM1 myotubes [33]. Here, ATP2A1 is linked to myotonic dystrophy type 1.