Trpc2-Expressing Sensory Neurons in the Main Olfactory Epithelium of the Mouse

• Olfaction initiates at the main olfactory epithelium and the vomeronasal epithelium
• Two types of Trpc2+ neurons in the mouse main olfactory epithelium are described
• Both cell types also express Cnga2 and can be distinguished by expression of Adcy3
• There are implications for the interpretation of the phenotypes of Trpc2-KO mice

SummaryThe mouse olfactory system contains two distinct chemosensory epithelia, the main olfactory epithelium (MOE) and the vomeronasal epithelium (VNE). Their sensory neurons express odorant receptor genes and vomeronasal receptor genes, respectively, and differ fundamentally in their signal transduction pathways. Genes required for chemosensory transduction are the cyclic nucleotide-gated channel subunit Cnga2 and the transient receptor potential cation channel Trpc2, respectively. Here, we document two previously unrecognized types of Trpc2+ neurons in the MOE of mice of various ages, including adults. These cell types express Cnga2 and can be distinguished by expression of adenylate cyclase Adcy3 (positive: type A; negative: type B). A third of MOE neurons that express the odorant receptor genes Olfr68/Olfr69 coexpress Trpc2 and are type A cells. In Trpc2-IRES-taulacZ gene-targeted mice, some labeled axons coalesce into glomeruli in the main olfactory bulb. Our findings have implications for the conventional VNE-centric interpretation of the behavioral phenotypes of Trpc2 knockout mice.

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