title: Comparative analysis of the paired immunoglobulin-like receptor (PILR) locus in six mammalian genomes: duplication, conversion, and the birth of new genes.
abstract: Manyaspects of the immune system are controlled by homologous cell surface receptors that mediate inhibitory and activating pathways. The paired immunoglobulin-like receptor (PILR) locus at 7q22 encodes both PILRA, an inhibitory receptor, and PILRB, its activating counterpart. Mouse Pilrb1 is a novel immune system regulator, and its ligand Cd99 participates in the recruitment of T-cells to inflamed tissue. We characterized the PILR locus in six mammalian genomes and investigated the structure and mRNA expression of human PILRB. Synteny at the PILR locus is conserved in the human, chimpanzee, dog, mouse and rat genomes. The absence of the PILR locus in opossum and chicken genomes suggests it arose after the divergence of placental and nonplacental mammals. In humans, a Williams-Beuren syndrome-related segmental duplication has created a complex chimeric transcript representing the predominantly expressed form of PILRB. Unlike PILRA, PILRB transcripts were detected in a wide variety of tissues including cells of the lymphoid lineage. In the mouse genome, a second activating gene, Pilrb2, and six pseudogenes were found. Extensive gene duplications in the rat genome have resulted in at least 27 Pilrb genes and or pseudogenes. Abundant gene duplication events involving novel CD99-related genes were also detected in the rat genome. In addition to duplication, we show that gene conversion has played a persistent role in the evolution of the PILR genes. Overall, we demonstrate that the PILR locus is dynamically evolving via multiple evolutionary mechanisms in several mammalian genomes.
authors.affiliation: Centre for Biomedical Research, Department of Biology, University of Victoria, British Columbia, Canada.
authors.forename: Michael D
authors.initials: MD
authors.lastname: Wilson
authors.forename: Joseph
authors.initials: J
authors.lastname: Cheung
authors.forename: Duane W
authors.initials: DW
authors.lastname: Martindale
authors.forename: Stephen W
authors.initials: SW
authors.lastname: Scherer
authors.forename: Ben F
authors.initials: BF
authors.lastname: Koop
mesh_terms: D000818:Animals; D001483:Base Sequence; D002897:Chromosomes, Human, Pair 7; D004285:Dogs; D019143:Evolution, Molecular; D005091:Exons; D005785:Gene Conversion; D020440:Gene Duplication; D016678:Genome; D006801:Humans; D008322:Mammals / Q000235:genetics*; D008562:Membrane Glycoproteins / Q000235:genetics; D051379:Mice; D008969:Molecular Sequence Data; D009893:Opossums / Q000235:genetics / Q000276:immunology; D002679:Pan troglodytes / Q000235:genetics / Q000276:immunology; D010802:Phylogeny; D051381:Rats; D011971:Receptors, Immunologic / Q000235:genetics*; D016415:Sequence Alignment
chemical_list: D008562:Membrane Glycoproteins; C404960:PILRB protein, human; D011971:Receptors, Immunologic