title: Fugu immunoglobulin D: a highly unusual gene with unprecedented duplications in its constant region.
abstract: We have isolated and characterized the cDNA that encodes IgD of fugu (Takifugu rubripes). Though the splicing of micro1 with the delta1 domain was similar to those reported for teleost IgDs, highly unusual and unprecedented domain duplications were found in the constant region of the fugu IgD. The structure of the fugu IgD is like VDJ-micro1-(delta1-delta2-delta3-delta4-delta5-delta6)(2)-delta7-deltam1-deltam2. Genomic sequence analysis of the fugu IgD gene supported the results of cDNA sequencing that the first six delta domains in the constant region are duplicated. Such a novel duplication pattern has not been reported in any other vertebrates. However, IgD secretory domains could not be identified in this study. The deduced amino acid sequence of the fugu IgD constant region showed high identity (35-55%) to the sequences of previously reported teleost IgDs. Gene expression analyses based on RT-PCR demonstrated that the IgD gene is preferentially expressed in presumptive lymphoid tissues; moreover, in situ hybridization showed that IgD-positive cells are distributed throughout the spleen and head kidney. The expression pattern is similar to that of IgM, corroborating the hypothesis that IgD plays an important role in the humoral immune system of this species.
authors.affiliation: Molecular Genetics Department, Benaroya Research Institute at Virginia Mason, 1201 Ninth Avenue, Seattle, WA 98101, USA.
authors.forename: Nil Ratan
authors.initials: NR
authors.lastname: Saha
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Suetake
authors.forename: Kiyoshi
authors.initials: K
authors.lastname: Kikuchi
authors.forename: Yuzuru
authors.initials: Y
authors.lastname: Suzuki
mesh_terms: D017398:Alternative Splicing; D000595:Amino Acid Sequence; D000818:Animals; D001483:Base Sequence; D003001:Cloning, Molecular; D018076:DNA, Complementary / Q000235:genetics; D005091:Exons / Q000235:genetics; D020440:Gene Duplication; D007127:Immunoglobulin Constant Regions / Q000235:genetics*; D007072:Immunoglobulin D / Q000235:genetics*; D007438:Introns / Q000235:genetics; D008969:Molecular Sequence Data; D017386:Sequence Homology, Amino Acid; D023741:Takifugu / Q000235:genetics* / Q000276:immunology*
chemical_list: D018076:DNA, Complementary; D007127:Immunoglobulin Constant Regions; D007072:Immunoglobulin D