Distribution of cells expressing vomeronasal receptors in the olfactory organof turtles

摘要

Generally, the olfactory organ of vertebrates consists of the olfactory epithelium (OE)and the vomeronasal organ (VNO). The OE contains ciliated olfactory receptor neurons(ORNs), while the VNO contains microvillous ORNs. The ORNs in the OE express odorantreceptors ( ), while those in the VNO express type 1 and type 2vomeronasal receptors ( and ). In turtles, theolfactory organ consists of the upper (UCE) and lower chamber epithelia (LCE). The UCEcontains ciliated ORNs, while the LCE contains microvillous ORNs. Here we investigated thedistribution of cells expressing vomeronasal receptors in the olfactory organ of turtles.The turtle vomeronasal receptors were encoded by two genes and two genes. Among them, and were mainly expressed in the LCE, while was expressed both in theUCE and LCE. Notably, vomeronasal receptors were expressed by a limited number of ORNs,which was confirmed by the expression of the gene encoding TRPC2, an ion channel involvedin the signal transduction of vomeronasal receptors. Furthermore, expression of by the majority of ORNs was suggested by the expression of the geneencoding CNGA2, an ion channel involved in the signal transduction of ORs. Thus, olfactionof turtle seems to be mediated mainly by the ORs rather than the vomeronasal receptors.More importantly, the relationship between the fine structure of ORNs and the expressionof olfactory receptors are not conserved among turtles and other vertebrates.