Polymorphism of the MHC class II DAB locus in swordtails Xiphophorus multilineatus and Xiphophorus pygmaeus / by Gerald A. Capraro, Jr.
| Author/creator | Capraro, Gerald A. author. |
| Other author | McConnell, Thomas J., degree supervisor. |
| Other author | East Carolina University. Department of Biology. |
| Format | Theses and dissertations |
| Production | 2002. |
| Description | 86 leaves : illustrations (some color) ; 28 cm |
| Supplemental Content | Access via ScholarShip |
| Subjects |
| Summary | Major histocompatibility complex (MHC) class II aP heterodimers on the surface of antigen presenting cells bind and present peptides to CD4⁺ T cells (Th). This is key in the activation of Th cells to initiate a specific immune response. Polymorphism, the presence in a population of many alleles at a given locus, manifests itself, with respect to MHC genes, as nonsynonymous nucleotide substitutions within regions encoding the peptide-binding domain of an MHC protein. This genetic variability within the MHC allows the organism to bind a wide repertoire of peptides. The DAB locus encodes a P-chain glycoprotein of the MHC class II heterodimer. We have cloned and sequenced cDNAs of DAB from two populations each of two species of swordtails, Xiphophorus multilineatus and X. pygmaeus, and compared them to determine the level of polymorphism. Analyses show nucleotide substitution patterns consistent with amino acid replacement at the putative peptide binding sites, as well as allelic lineages showing the persistence of these polymorphisms across species. Furthermore, phylogenetic analyses suggest that polymorphisms observed in these Xiphophorins are under positive selection. Evidence presented here also shows that the rates of synonymous substitution are higher within the peptide-binding region than elsewhere in the gene, similar to some mammalian species. Finally, the data observed within this study show evidence of at least two distinct DAB loci. Understanding the nature of the DAB locus will lead to a better understanding of the evolution of the Xiphophorus genus, as well as a clearer understanding of the gene duplication events that contributed to the evolution of the MHC in general. |
| General note | Presented to the faculty of the Department of Biology. |
| General note | Advisor: Thomas J. McConnell |
| Dissertation note | M.S. East Carolina University 2002 |
| Bibliography note | Includes bibliographical references (leaves 76-86). |
| Genre/form | Academic theses. |
| Genre/form | Academic theses. |
| Genre/form | Thèses et écrits académiques. |
Availability
| Library | Location | Call Number | Status | Item Actions |
|---|---|---|---|---|
| Joyner | University Archives | ASK AT SPECIAL COLLECTIONS DESK | ✔ Available | Request Material |
| Electronic Resources | Access Content Online | ✔ Available |