title: Definition of a third VLR gene in hagfish.
abstract: Jawless vertebrates (cyclostomes) have an alternative adaptive immune system in which lymphocytes somatically diversify their variable lymphocyte receptors (VLR) through recombinatorial use of leucine-rich repeat cassettes during VLR gene assembly. Three types of these anticipatory receptors in lampreys (VLRA, VLRB, and VLRC) are expressed by separate lymphocyte lineages. However, only two VLR genes (VLRA and VLRB) have been found in hagfish. Here we have identified a third hagfish VLR, which undergoes somatic assembly to generate sufficient diversity to encode a large repertoire of anticipatory receptors. Sequence analysis, structural comparison, and phylogenetic analysis indicate that the unique hagfish VLR is the counterpart of lamprey VLRA and the previously identified hagfish "VLRA" is the lamprey VLRC counterpart. The demonstration of three orthologous VLR genes in both lampreys and hagfish suggests that this anticipatory receptor system evolved in a common ancestor of the two cyclostome lineages around 480 Mya.
authors: Emory Vaccine Center and Department of Pathology and Laboratory Medicine, Emory University, Atlanta, GA 30322.
authors: Jianxu
authors: J
authors: Li
authors: Sabyasachi
authors: S
authors: Das
authors: Brantley R
authors: BR
authors: Herrin
authors: Masayuki
authors: M
authors: Hirano
authors: Max D
authors: MD
authors: Cooper
mesh_terms: D056704:Adaptive Immunity / Q000235:genetics*; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D018076:DNA, Complementary / Q000235:genetics; D019143:Evolution, Molecular; D029941:Fish Proteins / Q000737:chemistry / Q000235:genetics* / Q000276:immunology*; D006196:Hagfishes / Q000235:genetics* / Q000276:immunology*; D007798:Lampreys / Q000235:genetics / Q000276:immunology; D008214:Lymphocytes / Q000276:immunology; D008958:Models, Molecular; D008969:Molecular Sequence Data; D010802:Phylogeny; D011971:Receptors, Immunologic / Q000737:chemistry / Q000235:genetics*; D017386:Sequence Homology, Amino Acid; D059467:Transcriptome
chemical_list: D018076:DNA, Complementary; D029941:Fish Proteins; D011971:Receptors, Immunologic
keywords: adaptive immunity; agnatha; antigen receptor; molecular evolution
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