Analysis of the vomeronasal receptor repertoire, expression and allelic diversity in swine

• We conducted a genome level analysis of vomeronasal receptors in the pig genome
• We showed that only V1Rs are functional in pigs among the three types of VRs
• We revealed genetic diversity of V1Rs has been under strong purifying selection
• V1Rs are expressed at low level in all tissues examined, except for VNO and testes

Here we report a comprehensive analysis of the vomeronasal receptor repertoire in pigs. We identified a total of 25 V1R sequences consisting of 10 functional genes, 3 pseudogenes, and 12 partial genes, while functional V2R and FPR genes were not present in the pig genome. Pig V1Rs were classified into three subfamilies, D, F, and J. Using direct high resolution sequencing-based typing of all functional V1Rs from 10 individuals of 5 different breeds, a total of 24 SNPs were identified, indicating that the allelic diversity of V1Rs is much lower than that of the olfactory receptors. A high expression level of V1Rs was detected in the vomeronasal organ (VNO) and testes, while a low expression level of V1Rs was observed in all other tissues examined. Our results showed that pigs could serve as an interesting large animal model system to study pheromone-related neurobiology because of their genetic simplicity.