title: Analysis of immunoglobulin transcripts in the ostrich Struthio camelus, a primitive avian species.
abstract: Previous studies on the immunoglobulin (Ig) genes in avian species are limited (mainly to galliformes and anseriformes) but have revealed several interesting features, including the absence of the IgD and Igκ encoding genes, inversion of the IgA encoding gene and the use of gene conversion as the primary mechanism to generate an antibody repertoire. To better understand the Ig genes and their evolutionary development in birds, we analyzed the Ig genes in the ostrich (Struthio camelus), which is one of the most primitive birds. Similar to the chicken and duck, the ostrich expressed only three IgH chain isotypes (IgM, IgA and IgY) and λ light chains. The IgM and IgY constant domains are similar to their counterparts described in other vertebrates. Although conventional IgM, IgA and IgY cDNAs were identified in the ostrich, we also detected a transcript encoding a short membrane-bound form of IgA (lacking the last two C(H) exons) that was undetectable at the protein level. No IgD or κ encoding genes were identified. The presence of a single leader peptide in the expressed heavy chain and light chain V regions indicates that gene conversion also plays a major role in the generation of antibody diversity in the ostrich. Because the ostrich is one of the most primitive living aves, this study suggests that the distinct features of the bird Ig genes appeared very early during the divergence of the avian species and are thus shared by most, if not all, avian species.
authors.affiliation: State Key Laboratory of Agrobiotechnology, College of Biological Sciences, China Agricultural University, Beijing, People's Republic of China.
authors.forename: Tian
authors.initials: T
authors.lastname: Huang
authors.forename: Min
authors.initials: M
authors.lastname: Zhang
authors.forename: Zhiguo
authors.initials: Z
authors.lastname: Wei
authors.forename: Ping
authors.initials: P
authors.lastname: Wang
authors.forename: Yi
authors.initials: Y
authors.lastname: Sun
authors.forename: Xiaoxiang
authors.initials: X
authors.lastname: Hu
authors.forename: Liming
authors.initials: L
authors.lastname: Ren
authors.forename: Qingyong
authors.initials: Q
authors.lastname: Meng
authors.forename: Ran
authors.initials: R
authors.lastname: Zhang
authors.forename: Ying
authors.initials: Y
authors.lastname: Guo
authors.forename: Lennart
authors.initials: L
authors.lastname: Hammarstrom
authors.forename: Ning
authors.initials: N
authors.lastname: Li
authors.forename: Yaofeng
authors.initials: Y
authors.lastname: Zhao
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D018076:DNA, Complementary / Q000235:genetics; D019143:Evolution, Molecular; D005803:Genes, Immunoglobulin; D007143:Immunoglobulin Heavy Chains / Q000032:analysis / Q000235:genetics; D007132:Immunoglobulin Isotypes / Q000032:analysis / Q000235:genetics; D007147:Immunoglobulin Light Chains / Q000032:analysis / Q000235:genetics; D007136:Immunoglobulins / Q000032:analysis / Q000235:genetics*; D008969:Molecular Sequence Data; D010802:Phylogeny; D020310:Struthioniformes / Q000235:genetics*; D014158:Transcription, Genetic
chemical_list: D018076:DNA, Complementary; D007143:Immunoglobulin Heavy Chains; D007132:Immunoglobulin Isotypes; D007147:Immunoglobulin Light Chains; D007136:Immunoglobulins