Figure.

Classes of CFTR mutations. Class I and II mutations result in CFTR protein that does not reach the cell surface due to impaired protein translation in the cell nucleus (Class I) or misfolded protein in the golgi apparatus (Class II). Class III and IV mutations result in CFTR that reaches the cell surface but exhibits impaired function due to a gating defect (Class III) or decrease conductivity (Class IV). Class V mutations lead to a reduced production of normal CFTR.