CONNEXIN-26 EXPRESSION IN HUMAN AND FERRET AIRWAYS AND LUNG DURING DEVELOPMENT

Coordinated microscopic and molecular biological studies were used to document gap junction expression during postnatal development in ferre t tracheal epithelium and lung and in fetal and adult human airway and lung. Expression of connexin 26 (Cx26) in the ferret airways was limi ted to the epithelial layer and was observed only during the newborn i nterval. In contrast, we found Cx26 expressed in the alveolar epitheli um of the ferret lung by in situ hybridization, Northern blotting, RT- PCR amplification, and immunocytochemical labeling at all ages examine d. This finding was further confirmed by documentation of gap junction al plaques upon ultrastructural examination of freeze-fracture replica s of adult ferret lung tissue. Parallel studies of developing human fe tal lung and airway suggested connexin expression in the airways only in the first trimester but, as in the ferret, persistent expression wa s observed in both fetal and adult lung. These studies suggest that th e transient expression of Cx26 is a reliable early indicator of airway epithelial development and differentiation in the airways. In contras t, Cx26 expression persists throughout life in the lung, suggesting th at gap junctions serve more perennial intercellular communication func tions in the peripheral lung.