Mature olfactory receptor neurons express connexin 43

The expression of the gap junction subunit connexin 43 was studied in the o lfactory epithelium of adult mice. In agreement with conclusions from previ ous immunohistochemical studies, we observed expression of mRNA encoding fo r connexin 43 in layers of the epithelium containing nuclei belonging to su stentacular cells. However, we also observed expression of connexin 43 mRNA in the layers containing nuclei belonging to mature olfactory receptor neu rons (ORNs), immature ORNs, and basal cells. Connexin 43 mRNA expression wa s low in dorsomedial regions of the nasal cavity but higher ventrally. This differential regional distribution was consistent with expression in a tra nsgenic mouse of a LacZ reporter gene driven by the proximal 6.5 kb of the connexin 43 promoter. LacZ was expressed in cells colabeled with antibody a gainst olfactory marker protein (OMP), corroborating that mature ORNs expre ss connexin 43. LacZ staining also was observed in sustentacular and basal cells and in immature ORNs. Double-label studies with antibodies against co nnexin 43 and OMP and expression of connexin 43 in the epithelium of bulbec tomized mice were also consistent with expression of connexin 43 in mature ORNs. This is the first report of expression of a connexin subunit in matur e ORNs. Our findings of connexin subunits in mature ORNs raise the novel po ssibility that gap junctions may play a fundamental role in information pro cessing in the olfactory epithelium. (C) 2000 Wiley-Liss, Inc.