Expression of connexin 57 in the olfactory epithelium and olfactory bulb

In the visual system, deletion of connexin 57 (Cx57) reduces gap junction coupling among horizontal cells and results in smaller receptive fields. To explore potential functions of Cx57 in olfaction, in situ hybridization and immunohistochemistry methods were used to investigate expression of Cx57 in the olfactory epithelium and olfactory bulb. Hybridization signal was stronger in the olfactory epithelial layer compared to the connective tissue underneath. Within the sensory epithelial layer, hybridization signal was visible in sublayers containing cell bodies of basal cells and olfactory neurons but not evident at the apical sublayer comprising cell bodies of sustentacular cells. These Cx57 positive cells were clustered into small groups to form different patterns in the olfactory epithelium. However, individual patterns did not associate with specific regions of olfactory turbinates or specific olfactory receptor zones. Patched distribution of hybridization positive cells was also observed in the olfactory bulb and accessory olfactory bulb in layers where granule cells, mitral cells, and juxtaglomerular cells reside. Immunostaining was observed in the cell types described above but the intensity was weaker than that in the retina. This study has provided anatomical basis for future studies on the function of Cx57 in the olfactory system.