These include CLCA1, whose locus has been reported to modulate gastrointestinal defect in CF (Ritzka et al, 2004; Van Der Doef et al, 2010) (Fig 2E) and SLC4A4, which was found to modify the intestinal phenotype in CF (Dorfman et al, 2009) (Fig 2F). This evidence concerns the gene SLC4A4 and cystic fibrosis.