title: IgH loci of American alligator and saltwater crocodile shed light on IgA evolution.
abstract: Immunoglobulin loci of two representatives of the order Crocodylia were studied from full genome sequences. Both Alligator mississippiensis and Crocodylus porosus have 13 genes for the heavy chain constant regions of immunoglobulins. The IGHC locus contains genes encoding four immunoglobulins M (IgM), one immunoglobulin D (IgD), three immunoglobulins A (IgA), three immunoglobulins Y (IgY), and two immunoglobulins D2 (IgD2). IgA and IgD2 genes were found in reverse transcriptional orientation compared to the other Ig genes. The IGHD gene contains 11 exons, four of which containing stop codons or sequence alterations. As described in other reptiles, the IgD2 is a chimeric Ig with IgA- and IgD-related domains. This work clarifies the origin of bird IgA and its evolutionary relationship with amphibian immunoglobulin X (IgX) as well as their links with mammalian IgA.
authors.affiliation: Oceanographic Center of Vigo, Spanish Institute of Oceanography-IEO, Subida a Radio Faro 50, 36390 Vigo, Pontevedra, Spain.
authors.forename: Susana
authors.initials: S
authors.lastname: Magadán-Mompó
authors.forename: Christian
authors.initials: C
authors.lastname: Sánchez-Espinel
authors.forename: Francisco
authors.initials: F
authors.lastname: Gambón-Deza
mesh_terms: D000489:Alligators and Crocodiles / Q000235:genetics* / Q000276:immunology; D000595:Amino Acid Sequence; D000663:Amphibians / Q000235:genetics / Q000276:immunology; D000818:Animals; D001483:Base Sequence; D001717:Birds / Q000235:genetics / Q000276:immunology; D018388:Codon, Terminator; D017124:Conserved Sequence; D019143:Evolution, Molecular; D005091:Exons / Q000235:genetics; D005803:Genes, Immunoglobulin; D007070:Immunoglobulin A / Q000737:chemistry / Q000235:genetics*; D007143:Immunoglobulin Heavy Chains / Q000235:genetics*; D007136:Immunoglobulins / Q000737:chemistry / Q000235:genetics; D008322:Mammals / Q000235:genetics / Q000276:immunology; D008969:Molecular Sequence Data; D010802:Phylogeny; D017434:Protein Structure, Tertiary; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D013045:Species Specificity
chemical_list: D018388:Codon, Terminator; D007070:Immunoglobulin A; D007143:Immunoglobulin Heavy Chains; D007136:Immunoglobulins
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