CFTR and cystic fibrosis: Cystic fibrosis (CF), one of the most common inherited diseases (∼1/3000 in Caucasian populations), is caused by mutations in the CF transmembrane conductance regulator (CFTR) gene, which encodes for a cAMP-regulated chloride channel expressed at the apical surface of epithelial cells in the airways, intestine, pancreas, and other organs.