Sequence diversity and genomic organization of vomeronasal receptor genes in the mouse

The vomeronasal system of mice is thought to be specialized in the detection of pheromones. Two multigene families have been identified that encode proteins with seven putative transmembrane domains and that are expressed selectively in subsets of neurons of the vomeronasal organ. The products of these vomeronasal receptor (Vr) genes are regarded as candidate pheromone receptors. Little is known about their genomic organization and sequence diversity, and only five sequences of mouse Vlr coding regions are publicly available. Here, we have begun to characterize systematically the Vlr repertoire in the mouse, We isolated 107 bacterial artificial chromosomes (BACs) containing Vlr genes from a 129 mouse library. Hybridization experiments indicate that at least 107 Vlr-like sequences reside on these BACs. We assembled most of the BACs into six contigs, of which one major contig and one minor contig were characterized in detail. The major contig is 630-860 kb long, encompasses a cluster of 21-48 Vlr genes, and contains marker D6Mit227. Sequencing of the coding regions was facilitated by the absence of introns. We determined the sequence of rite coding region of 25 possibly functional Vlr genes and seven pseudogenes. The functional Vlrs can be arranged into three groups; Vlrs of one group are novel and substantially divergent From the other Vlrs. The genomic and sequence information described here should be useful in defining the biological function of these receptors.