Characterization of nonfunctional V1R-like pheromone receptor sequences in human

The vomeronasal organ (VNO) or Jacobson's organ is responsible in terrestrial vertebrates for the sensory perception of pheromones, chemicals that elicit stereotyped behaviors among individuals of the same species. Pheromone-induced behaviors and a functional VNO have been described in a number of mammals, 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 different human sequences by PCR and library screening with rodent sequences. These human sequences exhibit characteristic features of V1R receptors and show 52%-59% of amino acid sequence identity with the rat sequences. Using PCR on a monochromosomal somatic cell hybrid panel and/or FISH, we demonstrate that these V1R-like sequences are distributed on chromosomes 7, 16, 20, 13, 14, 15, 21, and 22 and possibly on additional chromosomes. One sequence hybridizes to pericentromeric locations on all the acrocentric chromosomes (13, 14, 15, 21, and 22). All of the seven V1R-like sequences analyzed show interrupted reading frames, indicating that they represent nonfunctional 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 functions of rodents.