title: Identification of sturgeon IgD bridges the evolutionary gap between elasmobranchs and teleosts.
abstract: IgD has been found in almost all jawed vertebrates, including cartilaginous and teleost fish. However, IgD is missing in acipenseriformes, a branch that is evolutionarily positioned between elasmobranchs and teleost fish. Here, by analyzing transcriptome data, we identified a transcriptionally active IgD-encoding gene in the Siberian sturgeon (Acipenser baerii). Phylogenetic analysis indicated that it is orthologous to mammalian IgD and closely related to the IgD of other fish. The lengths of sturgeon membrane-bound IgD transcripts ranged from 1.2kb to 6.2kb, encoding 3-19 CH domains. As in teleosts, the first CH domain of the sturgeon IgD transcript is also derived from μCH1 by RNA splicing. However, the variable region of the expressed sturgeon IgD shows limited V(D)J usage. In addition to IgD, three IgM variants were also identified in this species, whereas no IgT/Z-encoding genes were observed. This study bridges the gap in Ig evolution between elasmobranchs and teleosts and provides significant insight into the early evolution of immunoglobulins.
authors.affiliation: State Key Laboratory of Agrobiotechnology, College of Biological Sciences, National Engineering Laboratory for Animal Breeding, China Agricultural University, Beijing 100193, PR China.
authors.forename: Lin
authors.initials: L
authors.lastname: Zhu
authors.forename: Zhenxin
authors.initials: Z
authors.lastname: Yan
authors.forename: Mengyang
authors.initials: M
authors.lastname: Feng
authors.forename: Dezhi
authors.initials: D
authors.lastname: Peng
authors.forename: Ying
authors.initials: Y
authors.lastname: Guo
authors.forename: Xiaoxiang
authors.initials: X
authors.lastname: Hu
authors.forename: Liming
authors.initials: L
authors.lastname: Ren
authors.forename: Yi
authors.initials: Y
authors.lastname: Sun
mesh_terms: D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D005075:Biological Evolution; D018940:Elasmobranchii / Q000235:genetics* / Q000276:immunology; D029941:Fish Proteins; D020869:Gene Expression Profiling; D014644:Genetic Variation; D007072:Immunoglobulin D / Q000235:genetics* / Q000276:immunology; D007143:Immunoglobulin Heavy Chains / Q000235:genetics; D007075:Immunoglobulin M / Q000235:genetics* / Q000276:immunology; D007136:Immunoglobulins / Q000172:deficiency / Q000235:genetics; D010802:Phylogeny; D012326:RNA Splicing; D016415:Sequence Alignment; D017422:Sequence Analysis, DNA; D059467:Transcriptome / Q000235:genetics
chemical_list: D029941:Fish Proteins; D007072:Immunoglobulin D; D007143:Immunoglobulin Heavy Chains; D007075:Immunoglobulin M; D007136:Immunoglobulins; C569864:immunoglobulin T, teleost
keywords: CH; H chain C region; H chain J segment; H chain V region; IMGT; Ig; IgD; Immunoglobulin heavy chain; International ImMunoGeneTics database; JH; Siberian sturgeon; TM; VH; immunoglobulin; transmembrane region