Molecular genetic analysis of the swordtail major histocompatibility complex DXB locus / by Brandon J. Cuthbertson.
| Author/creator | Cuthbertson, Brandon J. author. |
| Other author | McConnell, Thomas J., degree supervisor. |
| Other author | East Carolina University. Department of Biology. |
| Format | Theses and dissertations |
| Production | 2000. |
| Description | 55 leaves : illustrations (some color) ; 28 cm |
| Supplemental Content | Access via ScholarShip |
| Subjects |
| Summary | Major histocompatibility complex (MHC) class II ap heterodimers bind and present peptides to CD4+ T-cells initiating a specific immune response. Classical MHC class IIB loci are poly morphic in tetrapods and bony fish. Specific polymorphisms in exon 2 at these loci are present in allelic lineages that are represented in closely related species. The DXB gene in Xiphophorus is similar in form to functional class II B genes described in other vertebrates, yet divergent from the paralogous Xiphophorus DAB locus. Given the characteristics that define classical MHC class IIB genes including locus composition we hypothesize that DXB encoded genes will exhibit extensive polymorphism particularly within the region encoding the putative (peptide binding region) PBR. As predicted, based on the assignment of the DXB locus to the MHC class II family, DXB is polymorphic in swordtails (X. pygmaeus and X multilineatus). Poly morphism is demonstrated at DXB as a high degree of non-synonymous nucleotide substitutions in tile putative peptide binding region, and exists in the form of allelic lineages as revealed by phylogenetic analysis of full-length DXB cDNA sequences. The DXB sequence from the guppy is closely related to some swordtail DXB alleles, which is surprising given the extent of polymorphism observed at DXB within the genus Xiphophorus. Evidence presented in this report indicates that DXB polymorphism is the result of positive selection on a putative DXB protein implying a classical function. Analysis of DXB cDNA clones revealed three different alternate DXB transcripts that represent deletions of the dominant, full-length transcript. Evidence presented here implies that two alternate forms of DXB have arisen as products of alternate splicing and surest they may result in expression of novel putative p-chains with altered structure and function. |
| General note | Submitted to the faculty of the Department of Biology. |
| General note | Advisor: Thomas J. McConnell |
| Dissertation note | M.S. East Carolina University 2000 |
| Bibliography note | Includes bibliographical references (leaves 53-55). |
| Genre/form | Academic theses. |
| Genre/form | Academic theses. |
| Genre/form | Thèses et écrits académiques. |
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