Characterization of nonfunctional V1R-like pheromone receptor sequences inhuman

The vomeronasal organ (VNO) or Jacobson's organ is responsible in terrestri al Vertebrates for the sensory perception of pheromones, chemicals that eli cit stereotyped behaviors among individuals of the same species. Pheromone- induced behaviors and a functional VNO have been described in a number of m ammals, but the existence of this sensory system in human is still debated. Recently, two nonhomologous gene families, V1R and V2R, encoding pheromone receptors have been identified in rat. These receptors belong to the seven -transmembrane domain G-protein-coupled receptor superfamily. We sought to characterize V1R-like genes in the human genome. We have identified seven d ifferent human sequences by PCR and library screening with rodent sequences . These human sequences exhibit characteristic features of V1R receptors an d show 52%-59% of amino acid sequence identity with the rat sequences. Usin g PCR on a monochromosomal somatic cell hybrid panel and/or FISH, we demons trate that these VIR-like sequences are distributed on chromosomes 7, 16, 2 0, 13, 14, 15, 21, and 22 and possibly on additional chromosomes. One seque nce hybridizes to pericentromeric Locations on all the acrocentric chromoso mes (13, 14, 15, 21, and 22). All of the seven V1R-like sequences analyzed show interrupted reading Frames, indicating that they represent nonfunction al pseudogenes. The preponderence of pseudogenes among human V1R sequences and the striking anatomical differences between rodent and human VNO raise the possibility that humans may have lost the V1R/VNO-mediated sensory func tions of rodents.