CFTR and cystic fibrosis: They started by characterizing natural mutations in F9 exon 5, CFTR exon 12 and SMN2 exon 7 associated with exon skipping in Hemophilia B, Cystic fibrosis (CF), and Spinal muscular atrophy (SMA), respectively and then tried its therapeutic splicing rescue by using different ExSpeU1s.