title: Evolution of spatially coexpressed families of type-2 vomeronasal receptors in rodents.
abstract: The vomeronasal organ (VNO) is an olfactory structure for the detection of pheromones. VNO neurons express three groups of unrelated G-protein-coupled receptors. Type-2 vomeronasal receptors (V2Rs) are specifically localized in the basal neurons of the VNO and are believed to sense protein pheromones eliciting specific reproductive behaviors. In murine species, V2Rs are organized into four families. Family-ABD V2Rs are expressed monogenically and coexpress with family-C V2Rs of either subfamily C1 (V2RC1) or subfamily C2 (V2RC2), according to a coordinate temporal diagram. Neurons expressing the phylogenetically ancient V2RC1 coexpress family-BD V2Rs or a specific group of subfamily-A V2Rs (V2RA8-10), whereas a second neuronal subset (V2RC2-positive) coexpresses a recently expanded group of five subfamily-A V2Rs (V2RA1-5) along with vomeronasal-specific Major Histocompatibility Complex molecules (H2-Mv). Through database mining and Sanger sequencing, we have analyzed the onset, diversification, and expansion of the V2R-families throughout the phylogeny of Rodentia. Our results suggest that the separation of V2RC1 and V2RC2 occurred in a Cricetidae ancestor in coincidence with the evolution of the H2-Mv genes; this phylogenetic event did not correspond with the origin of the coexpressing V2RA1-5 genes, which dates back to an ancestral myomorphan lineage. Interestingly, the evolution of receptors within the V2RA1-5 group may be implicated in the origin and diversification of some of the V2R putative cognate ligands, the exocrine secreting peptides. The establishment of V2RC2, which probably reflects the complex expansion and diversification of family-A V2Rs, generated receptors that have probably acquired a more subtle functional specificity.
authors.affiliation: Department of Neuroscience, University of Parma, Italy.
authors.forename: Simona
authors.initials: S
authors.lastname: Francia
authors.affiliation: Department of Neuroscience, University of Parma, Italy.
authors.forename: Lucia
authors.initials: L
authors.lastname: Silvotti
authors.affiliation: Department of Neuroscience, University of Parma, Italy.
authors.forename: Filippo
authors.initials: F
authors.lastname: Ghirardi
authors.affiliation: Laboratoire de Paleontologie, Institut des Sciences de l'Evolution, UMR 5554 Centre National de la Recherche Scientifique, Université de Montpellier 2, France.
authors.forename: François
authors.initials: F
authors.lastname: Catzeflis
authors.affiliation: Department of Life Sciences, University of Parma, Italy.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Percudani
authors.affiliation: Department of Neuroscience, University of Parma, Italy robertin@unipr.it.
authors.forename: Roberto
authors.initials: R
authors.lastname: Tirindelli
mesh_terms: D000818:Animals; D019143:Evolution, Molecular; D008285:Major Histocompatibility Complex / Q000235:genetics; D051379:Mice; D010675:Pheromones / Q000235:genetics; D010802:Phylogeny; D043563:Receptors, Pheromone / Q000235:genetics* / Q000502:physiology; D012377:Rodentia / Q000235:genetics*; D019147:Vomeronasal Organ / Q000502:physiology
chemical_list: D010675:Pheromones; D043563:Receptors, Pheromone
keywords: chemosensory; evolution; pheromones; phylogeny; rodents; vomeronasal