Widely used mouse models for DMD preclinical studies include the dystrophin deficient mdx mouse (Bulfield et al., 1984; Yucel et al., 2018) and the dystrophin deficient and utrophin haplo-insufficient (utrn+/–; mdx) “het” mouse (Zhou et al., 2008; van Putten et al., 2012). The gene discussed is UTRN; the disease is Duchenne muscular dystrophy.