As an example, SpCas9 and one sgRNA targeting the splice donor site of exon 44 induces ~60% of dystrophin-positive myofibers in skeletal muscles of DMD ΔEx45 mice, but the same SpCas9 system merely restores dystrophin expression in ~36% of myofibers of a DMD ΔEx43 mouse model [134]. This evidence concerns the gene DMD and Duchenne muscular dystrophy.