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Studies of immunoglobulin light chains in rainbow trout (Oncorhynchus mykiss): new insight into the evolution of immunoglobulin genes
Uppsala University, Teknisk-naturvetenskapliga vetenskapsområdet, Faculty of Science and Technology, Biology, Department of Cell and Molecular Biology.
2002 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

In this thesis, the structure and the expression of immunoglobulin (Ig) light chain genes were studied in rainbow trout and including an evolutionary perspective. A novel Ig light chain locus (IgL2) was identified and characterized. As an expansion of this study, the genomic organization of two Ig light chains was settled in genomic clones, some putative transcription regulatory elements were identified and the expression of L1 and L2 was studied in several tissues. In order to study expression of L1 and L2 at the protein level, monoclonal antibodies were generated, using DNA immunization. The contribution of different IgL isotypes in the antibody response against a fish rhabdovirus was investigated. This study demonstrated that the variability of L1 and L2 was modified in different manners. Genomic clones for a third trout light chain (IgL3) were isolated, and the sequence of the putative promoter regions of the three isotypes were compared. The L1 and L3 promoters have a classical Ig promoter structure (i.e. with TATA-box, E-box, and octamer) whereas the L2 promoter lacks the typical features of an Ig promoter. The IgL2 promoter region contained a κ-Y motif and an E-box. Cell transfection studies using different deletion constructs demonstrated that the κ-Y element drives the transcriptional activity of L2 promoter. Both the L1 and L2 promoters can cooperate with a B cell specific enhancer from cod, suggesting that common transcription factors are used.

L1 is most similar to the κ isotype found in mammals whereas L2 shows many features that deviate from this branch and the λ branch and forms a separate branch. The similarity between the L1C and L2C of trout Ig is about 30%. Thus, a sequence comparison of L1C regions with L3C regions shows a continuous transition in identity percentages, whereas the L2C appears not closely related to any C segment from another isotype. These results pave the way for a comprehensive understanding of the evolution, regulation and functions of light chains in a primitive vertebrate the rainbow trout, and other fish species.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis , 2002. , 57 p.
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 707
Keyword [en]
Cell and molecular biology, Immunoglobulin genes, gene organization, evolution, comparative immunology, promoter, rainbow trout (Oncorhynchus mykiss)
Keyword [sv]
Cell- och molekylärbiologi
National Category
Biochemistry and Molecular Biology
Research subject
Molecular Immunology
URN: urn:nbn:se:uu:diva-1982ISBN: 91-554-530-5OAI: oai:DiVA.org:uu-1982DiVA: diva2:161584
Public defence
2002-05-17, lecture hall C10:305 at the Biomedical Center (BMC), Uppsala, 09:15
Available from: 2002-04-26 Created: 2002-04-26Bibliographically approved

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