ACTN3 and Duchenne muscular dystrophy: Furthermore, genes annotated to increase fiber composition and confer calcium‐sensitivity to skeletal muscle such as α‐actinin‐3 (ACTN3), Duchenne muscular dystrophy (DMD), nebulin (NEB), slow skeletal muscle troponin T1 and T3 (TNNT1/3), troponin I2 (TNNI2), troponin C1 (TNNC1), and titin (TTN) were also significantly upregulated in both young and old derived myobundles.