MGI:99659Homozygotes for a targeted null mutation and a similar ENU-induced mutation are born with a rounded body shape, edema, thin and misshapened ribs, and abnormal muscle fibers. Mutants die perinatally. Compound heterozygosity for the p.Q1971Tfs*49 and p.A4330D mutations affects muscle calcium ion kinetics and leads to reduced body weight and muscle strength.