Bioinformatic Analysis of the Swine Genome Identified 1307 Genes Encoding for Olfactory Receptors

Mammalian olfactory receptors (ORs) are encoded by the largest multigene family in the genomes of mammals. We report here the result of a whole genome scanning of olfactory receptor genes in the pig using conserved OR sequence motifs and their variants derived from transmembrane 3, 6, 7 and a GN motif. Using these conserved motifs, we had identified 1307 OR related sequences including 1,121 functional OR genes, 186 pseudogenes and 357 partial genes from the swine genome assembly build 10.2. OR genes were located in 98 different loci on 16 pig chromosomes. We classified these genes into 17 families consisting 2 classes with 3 families for class I and 14 for class II, respectively. Consistent to the results from human and mouse studies, most of pig subfamilies were also encoded within a single locus, supporting that the structural features to recognize different types of odorant molecules may be encoded by different loci. Moreover, we found 9 and 125 sets of inter- and intra-chromosomal duplications of OR genes, respectively, in 12 chromosomes. More interestingly, we found 212 OR sequences which are specific for pigs and they may have special potential functions limited in pigs. We hope that our study will help to understand the biological aspect of OR genes in the pig and possible association with production traits such as reproduction efficiency.