NOS1 and Duchenne muscular dystrophy: R16/17 protein therapy alone cannot restore sarcolemmal nNOS in DMD; C, In ΔR4 mice, ΔR4 micro-dystrophin recruits syntrophin to the muscle membrane, and sarcolemmal nNOS is still absent since R16/17 domain is deleted in ΔR4 micro-dystrophin.