Cystic fibrosis is a heterogeneous condition caused by mutations in the cystic fibrosis transmembrane conductance regulator (CFTR) gene.¹ The gene product, a regulated chloride channel, is expressed in the apical plasma membrane of secretory and reabsorptive epithelia of affected organs and allows the transepithelial movement of water and solute by mediating chloride translocation across the plasma membrane. Although the mechanism underlying the CFTR-induced regulation of chloride transport activity has largely been elucidated, other effector functions are less well understood.

More than 1000 alterations have been identified in the CFTR gene (for a list, see http://www.genet.sickkids.on.ca/cftr/). Cystic fibrosis is . . .