CAPN3 and muscular dystrophy: Previousstudies performed on Capn3 knockout mice describe a reduced expression ofthe ryanodine receptor type 1 (RyR1) and reduced Ca2+ release from thesarcoplasmic reticulum (SR) to cytoplasm (Refs 3,4), suggesting that dysregulation ofCa2+ homeostasis plays a role in the pathogenic mechanisms involved in this formof muscular dystrophy (Ref.