Two similar studies have described using the CRISPR/Cas9 system in vivo to increase expression of the dystrophin gene and improve muscle function in mouse models of DMD.6, 7 Other studies have used CRISPR/Cas9 to target duplication of exons in the human dystrophin gene in vitro and have shown that this approach can lead to production of full-length dystrophin in the myotubules of an individual with DMD.8 The gene discussed is DMD; the disease is Duchenne muscular dystrophy.