CF is caused by variants in the gene encoding the CF transmembrane conductance regulator (CFTR) protein, a cAMP-regulated chloride (Cl−) and bicarbonate (HCO3−) channel expressed at the apical plasma membrane (PM) of epithelial cells (Riordan et al., 1989; Sheppard and Welsh, 1999). This evidence concerns the gene CFTR and cystic fibrosis.