Identification of sturgeon IgD bridges the evolutionary gap between elasmobranchs and teleosts.
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.
['Zhu|Lin|L|', 'Yan|Zhenxin|Z|', 'Feng|Mengyang|M|', 'Peng|Dezhi|D|', 'Guo|Ying|Y|', 'Hu|Xiaoxiang|X|', 'Ren|Liming|L|', 'Sun|Yi|Y|']
D000595:Amino Acid Sequence D000818:Animals D001483:Base Sequence D005075:Biological Evolution D018940:Elasmobranchii D029941:Fish Proteins D020869:Gene Expression Profiling D014644:Genetic Variation D007072:Immunoglobulin D D007143:Immunoglobulin Heavy Chains D007075:Immunoglobulin M D007136:Immunoglobulins D010802:Phylogeny D012326:RNA Splicing D016415:Sequence Alignment D017422:Sequence Analysis, DNA D059467:Transcriptome
IgD Siberian sturgeon CH Ig immunoglobulin H chain C region H chain J segment H chain V region IMGT Immunoglobulin heavy chain International ImMunoGeneTics database JH TM VH transmembrane region