title: Identification of diversified genes that contain immunoglobulin-like variable regions in a protochordate.
abstract: The evolutionary origin of adaptive immune receptors is not understood below the phylogenetic level of the jawed vertebrates. We describe here a strategy for the selective cloning of cDNAs encoding secreted or transmembrane proteins that uses a bacterial plasmid (Amptrap) with a defective beta-lactamase gene. This method requires knowledge of only a single target motif that corresponds to as few as three amino acids; it was validated with major histocompatibility complex genes from a cartilaginous fish. Using this approach, we identified families of genes encoding secreted proteins with two diversified immunoglobulin-like variable (V) domains and a chitin-binding domain in amphioxus, a protochordate. Thus, multigenic families encoding diversified V regions exist in a species lacking an adaptive immune response.
authors.affiliation: Immunology Program, H. Lee Moffitt Cancer Center and Research Institute, 12902 Magnolia Avenue, Tampa, FL 33612, USA.
authors.forename: John P
authors.initials: JP
authors.lastname: Cannon
authors.forename: Robert N
authors.initials: RN
authors.lastname: Haire
authors.forename: Gary W
authors.initials: GW
authors.lastname: Litman
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D004447:Echinodermata / Q000235:genetics / Q000276:immunology; D005803:Genes, Immunoglobulin; D007109:Immunity / Q000235:genetics*; D007135:Immunoglobulin Variable Region / Q000235:genetics*; D008969:Molecular Sequence Data; D005810:Multigene Family; D010802:Phylogeny; D011971:Receptors, Immunologic / Q000235:genetics
chemical_list: D007135:Immunoglobulin Variable Region; D011971:Receptors, Immunologic