Because nNOS is displaced in dystrophin-deficient skeletal muscle cells, nNOS activity levels are considerably lower in DMD patients and mdx mice, although nNOS deficiency is not due solely to lack of dystrophin in localizing the protein to the membrane as mRNA level of nNOS was also reduced in muscle biopsy of DMD patients and mdx mouse muscle [115]. The gene discussed is DMD; the disease is Duchenne muscular dystrophy.