title: Artiodactyl IgD: the missing link.
abstract: IgD has been suggested to be a recently developed Ig class, only present in rodents and primates. However, in this paper the cow, sheep, and pig Ig delta genes have been identified and shown to be transcriptionally active. The deduced amino acid sequences from their cDNAs show that artiodactyl IgD H chains are structurally similar to human IgD, where the cow, sheep, and pig IgD H chain constant regions all contain three domains and a hinge region, sharing homologies of 43.6, 44, and 46.8% with their human counterpart, respectively. According to a phylogenetic analysis, the Cdelta gene appears to have been duplicated from the Cmu gene >300 million yr ago. The ruminant mu CH1 exon and its upstream region was again duplicated before the speciation of the cow and sheep, approximately 20 million yr ago, inserted upstream of the delta gene hinge regions, and later modified by gene conversion. A short Sdelta (switch delta) sequence resulting from the second duplication, is located immediately upstream of the bovine Cdelta gene and directs regular mu-delta class switch recombination in the cow. The presence of Cdelta genes in artiodactyls, possibly in most mammals, suggests that IgD may have some as yet unknown biological properties, distinct from those of IgM, conferring a survival advantage.
authors.affiliation: Center for Biotechnology, Department of Bioscience at Novum, Karolinska Institute, SE-14157 Huddinge, Sweden. yafe@csb.ki.se
authors.forename: Yaofeng
authors.initials: Y
authors.lastname: Zhao
authors.forename: Imre
authors.initials: I
authors.lastname: Kacskovics
authors.forename: Qiang
authors.initials: Q
authors.lastname: Pan
authors.forename: David A
authors.initials: DA
authors.lastname: Liberles
authors.forename: Janos
authors.initials: J
authors.lastname: Geli
authors.forename: Scott K
authors.initials: SK
authors.lastname: Davis
authors.forename: Hodjattallah
authors.initials: H
authors.lastname: Rabbani
authors.forename: Lennart
authors.initials: L
authors.lastname: Hammarstrom
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001188:Artiodactyla / Q000235:genetics* / Q000276:immunology*; D001483:Base Sequence; D002417:Cattle; D003001:Cloning, Molecular / Q000379:methods; D018076:DNA, Complementary / Q000302:isolation & purification; D020440:Gene Duplication; D006801:Humans; D007059:Ictaluridae; D017578:Immunoglobulin Class Switching / Q000235:genetics; D007127:Immunoglobulin Constant Regions / Q000235:genetics / Q000302:isolation & purification; D007072:Immunoglobulin D / Q000737:chemistry / Q000235:genetics* / Q000302:isolation & purification; D007143:Immunoglobulin Heavy Chains / Q000235:genetics / Q000302:isolation & purification; D007138:Immunoglobulin delta-Chains / Q000235:genetics / Q000302:isolation & purification; D007148:Immunoglobulin mu-Chains / Q000235:genetics / Q000302:isolation & purification; D007438:Introns / Q000235:genetics; D051379:Mice; D008969:Molecular Sequence Data; D010802:Phylogeny; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D012689:Sequence Homology, Nucleic Acid; D012756:Sheep; D013552:Swine
chemical_list: D018076:DNA, Complementary; D007127:Immunoglobulin Constant Regions; D007072:Immunoglobulin D; D007143:Immunoglobulin Heavy Chains; D007138:Immunoglobulin delta-Chains; D007148:Immunoglobulin mu-Chains