title: Variable lymphocyte receptors in hagfish.
abstract: A previously uncharacterized type of variable lymphocyte receptors (VLR) was identified recently in the Sea lamprey. This jawless vertebrate generates an extensive VLR repertoire through differential insertion of neighboring diverse leucine-rich repeat (LRR) cassettes into an incomplete germ-line VLR gene. We report here VLR homologs from two additional lamprey species and the presence of two types of VLR genes in hagfish, the only other order of contemporary jawless vertebrates. As in the Sea lamprey, the incomplete hagfish germ-line VLR-A and -B genes are modified in lymphocyte-like cells to generate highly diverse repertoires of VLR-A and -B proteins via a presently undetermined mechanism. This jawless-fish mode of VLR diversification starkly contrasts with the rearrangement of Ig V(D)J gene segments used by all jawed vertebrates to produce diverse repertoires of T and B lymphocyte antigen receptors. The development of two very different strategies for receptor diversification at the dawn of vertebrate evolution approximately 500 million years ago attests to the fitness value of a lymphocyte-based system of anticipatory immunity.
authors.affiliation: Division of Developmental and Clinical Immunology, Department of Medicine, University of Alabama, Birmingham, AL 35294, USA.
authors.forename: Zeev
authors.initials: Z
authors.lastname: Pancer
authors.forename: Nil Ratan
authors.initials: NR
authors.lastname: Saha
authors.forename: Jun
authors.initials: J
authors.lastname: Kasamatsu
authors.forename: Takashi
authors.initials: T
authors.lastname: Suzuki
authors.forename: Chris T
authors.initials: CT
authors.lastname: Amemiya
authors.forename: Masanori
authors.initials: M
authors.lastname: Kasahara
authors.forename: Max D
authors.initials: MD
authors.lastname: Cooper
mesh_terms: D020816:Amino Acid Motifs; D000595:Amino Acid Sequence; D000818:Animals; D022202:Chromosomes, Artificial, Bacterial; D003001:Cloning, Molecular; D030541:Databases, Genetic; D019143:Evolution, Molecular; D015723:Gene Library; D006196:Hagfishes; D007930:Leucine / Q000737:chemistry; D008214:Lymphocytes / Q000378:metabolism*; D008957:Models, Genetic; D008969:Molecular Sequence Data; D010802:Phylogeny; D017434:Protein Structure, Tertiary; D011946:Receptors, Antigen / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D017386:Sequence Homology, Amino Acid; D045567:VDJ Recombinases / Q000378:metabolism
chemical_list: D011946:Receptors, Antigen; D045567:VDJ Recombinases; D007930:Leucine