Sexual dimorphism and developmental expression of signal-transduction machinery in the vomeronasal organ

We have explored the use of a new model to study the transduction of chemos ignals in the vomeronasal organ (VNO), for which the functional pathway for chemical communication is incompletely understood. Because putative vomero nasal receptors in mammalian and other vertebrate models belong to the supe rfamily of G-protein-coupled receptors, the objective of the present study was to define which G-protein subunits were present in the VNO of Sternothe rus odoratus (stinkpot or musk turtle) in order to provide directionality f or future functional studies of the downstream signaling cascades. The turt le vomeronasal epithelium (VNE) was found to contain the G-proteins G(beta) and G(alpha i1-3) at the microvillar layer, the presumed site of signal tr anduction in these neurons, as evidenced by immunocytochemical techniques. G(alpha0) labeled the axon bundles in the VNE and the somata of the vomeron asal sensory neurons but not the microvillar layer. Densitometric analysis of Western blots indicated that the VNO from females contained greater conc entrations of G(alpha i1-3) compared with males. Sexually immature (juvenil e) turtles showed intense immunolabeling for all three subunits (G(beta), G (alpha i1-3), and G(alpha0)) in the axon bundles and an absence of labeling in the microvillar layer. Another putative signaling component found in th e microvilli of mammalian VNO, transient receptor potential channel, was al so immunoreactive in S. odoratus in a gender-specific manner, as quantified by Western blot analysis. These data demonstrate the utility of Sternother us for discerning the functional signal transduction machinery in the VNO a nd may suggest that gender and developmental differences in effector protei ns or cellular signaling components may be used to activate sex-specific be haviors. (C) 2001 Wiley-Liss, Inc.