Consistent with earlier reports5, histological analysis of muscles from 20 weeks old Chkb−/− mice revealed extensive muscle wasting and extreme fatty infiltration in hindlimb; to evaluate the early signs of muscular dystrophy we performed histology on cross sections of hindlimb (gastrocnemius) and forelimb (triceps) muscles from 25-day old Chkb+/+, Chkb+/−and Chkb+/− mice (Supplementary Fig. 2A-C). This evidence concerns the gene CHKB and muscular dystrophy.