CFTR and cystic fibrosis: Our prior studies of cigarette smoke exposure in non-CF A/J mice have provided key evidence underscoring the causal relationship between smoking and CFTR abnormalities, demonstrating significant decrement in CFTR activity in the nasal airway (25–35% of air control), tracheal tissue (50–60%), and intestinal tissue (80–90%) after five weeks of smoke exposure [9].