Evolution of the Neuropeptide Y Receptor Family: Gene and Chromosome Duplications Deduced from the Cloning and Mapping of the Five Receptor Subtype Genes in Pig

Neuropeptide Y (NPY) receptors mediate a variety of physiological responses including feeding and vasoconstriction. To investigate the evolutionary events that have generated this receptor family, we have sequenced and determined the chromosomal localizations of all five presently known mammalian NPY receptor subtype genes in the domestic pig, Sus scrofa (SSC). The orthologs of the Y 1 and Y 2 subtypes display high amino acid sequence identities between pig, human, and mouse (92%–94%), whereas the Y 4 , Y 5 , and y 6 subtypes display lower identities (76%–87%). The lower identity of Y 5 is due to high sequence divergence in the large third intracellular loop. The NPY1R, NPY2R , and NPY5R receptor genes were localized to SSC8, the NPY4R to SSC14 , and NPY6R to SSC2. Our comparisons strongly suggest that the tight cluster of NPY1R, NPY2R , and NPY5R on human chromosome 4 (HSA4) represents the ancestral configuration, whereas the porcine cluster has been split by two inversions on SSC8. These 3 genes, along with adjacent genes from 14 other gene families, form a cluster on HSA4 with extensive similarities to a cluster on HSA5, where NPY6R and >13 other paralogs reside, as well as another large cluster on HSA10 that includes NPY4R . Thus, these gene families have expanded through large-scale duplications. The sequence comparisons show that the NPY receptor triplet NPY1R – NPY2R – NPY5R existed before these large-scale duplications. [Sequence data for this article were deposited with the GenBank data library under accession nos. AF106081 , PID g6457648 (for Pig Y1 sequence); accession nos. AF106082 , PID g4249727 (for Pig Y2 sequence); accession no. AF227955 (for Pig Y4 sequence); accession nos. AF106083 , PID g4249729 (for Pig Y5 sequence); accession no. AF227956 (for Pig Y6 sequence).]