Much success has been achieved by three independent research groups, demonstrating that CRISPR/Cas9-mediated genome editing was able to correct the defective dystrophin gene in in vivo mice models of DMD, which was shown by improved muscle structure and function [48,49,50] For instance, in order to demonstrate proof-of-concept that correction of the disease causing mutation for DMD can restore dystrophin expression in vivo, Long et al. utilized a postnatal mdx mice model harboring a frame shift mutation in exon 23 of the gene. This evidence concerns the gene DMD and Duchenne muscular dystrophy.