SRSF4 and cystic fibrosis: For example, SRSF1 (SF2/ASF), SRSF4 (SRp75), SRSF5 (SRp40), and SRSF6 (SRp55) are able to bind an ISS located in the intron 9 of the CFTR transcript and to skip the exon 9 causing the production of a nonfunctional protein associated with cystic fibrosis development (Pagani et al., 2000).