Immunohistochemical detection and regulation of α(5 )nicotinic acetylcholine receptor (nAChR) subunits by FoxA2 during mouse lung organogenesis

BACKGROUND: α(5 )nicotinic acetylcholine receptor (nAChR) subunits structurally stabilize functional nAChRs in many non-neuronal tissue types. The expression of α(5 )nAChR subunits and cell-specific markers were assessed during lung morphogenesis by co-localizing immunohistochemistry from embryonic day (E) 13.5 to post natal day (PN) 20. Transcriptional control of α(5 )nAChR expression by FoxA2 and GATA-6 was determined by reporter gene assays. RESULTS: Steady expression of α(5 )nAChR subunits was observed in distal lung epithelial cells during development while proximal lung expression significantly alternates between abundant prenatal expression, absence at PN4 and PN10, and a return to intense expression at PN20. α(5 )expression was most abundant on luminal edges of alveolar type (AT) I and ATII cells, non-ciliated Clara cells, and ciliated cells in the proximal lung at various periods of lung formation. Expression of α(5 )nAChR subunits correlated with cell differentiation and reporter gene assays suggest expression of α(5 )is regulated in part by FoxA2, with possible cooperation by GATA-6. CONCLUSIONS: Our data reveal a highly regulated temporal-spatial pattern of α(5 )nAChR subunit expression during important periods of lung morphogenesis. Due to specific regulation by FoxA2 and distinct identification of α(5 )in alveolar epithelium and Clara cells, future studies may identify possible mechanisms of cell differentiation and lung homeostasis mediated at least in part by α(5)-containing nAChRs.