| dc.contributor.author | Hrytsenko, Olga. | en_US |
| dc.date.accessioned | 2014-10-21T12:33:53Z | |
| dc.date.available | 2007 | |
| dc.date.issued | 2007 | en_US |
| dc.identifier.other | AAINR31487 | en_US |
| dc.identifier.uri | http://hdl.handle.net/10222/54949 | |
| dc.description | The Nile tilapia (Oreochromis niloticus) is one of the most important fish species for the aquaculture industry worldwide. It is also a popular model/organism in different areas of endocrinology, genetics, and physiology. Recently, it became a source of pancreatic islet tissue for xenotransplantation research and potentially for the treatment of insulin-dependent diabetes mellitus. To estimate the usefulness of the tilapia pancreatic islets in diabetic research it is important to understand both the differences and similarities in regulation of energy homeostasis between mammals and fish. This study focuses on characterization of the tilapia insulin, a pancreatic islet hormone that plays a central role in maintaining glucose homeostasis. Using different molecular techniques, we examined expression, genomic localization, and allelic and non-allelic polymorphisms of the insulin gene in tilapia. | en_US |
| dc.description | In contrast to the genomes of most mammalian species, the tilapia genome contains two insulin genes. The insulin 1 gene is located on the long arm of chromosome 1 (sex chromosome) and exists in three allelic variations. Two of the insulin 1 alleles were found in the genome of both male and female fish. The third one was preferentially observed in the male genome. The differences amongst insulin 1 alleles are comprised of sequences 2.3 kb upstream of the insulin 1 gene. | en_US |
| dc.description | Analysis of the tissue distribution of the insulin 1 and 2 mRNA revealed that expressions of both insulin genes are not strictly restricted to pancreatic beta-cells, as it is traditionally accepted for adult mammalian species. The insulin 1 gene is expressed predominantly in beta-cells of pancreatic islets but also in some other extrapancreatic tissues including pituitary gland, brain, and gonads. A low level of insulin 2 gene expression was detected in almost all tissues tested. | en_US |
| dc.description | Unlike short mammalian insulin promoters (400 bp) that are sufficient to activate high levels of beta-cell-specific transcription, the high level of the tilapia insulin 1 expression in the beta-cells required cooperative interactions between regulatory elements within the proximal and distal promoter regions. Moreover, it is likely that the gender-related sequences located 2.3 kb upstream of the insulin 1 gene are also involved in regulation of its expression and induce different levels of insulin 1 transcription in tilapia gonads and in tilapia fry prior to sex differentiation. The former finding together with detections of low levels of insulin 1 expression in the gonadotropin-producing cells of the tilapia pituitary gland, and with localization of the insulin 1 gene on the sex chromosome, indicate that insulin 1 might have acquired sex-related functions in tilapia. | en_US |
| dc.description | Similar to mammalian beta-cells, tilapia beta-cells, when exposed to stimulatory concentrations of nutrients, were able to evoke insulin exocytosis and to maintain intracellular insulin content at a constant level. However, in contrast to the elevation of insulin mRNA levels in mammalian beta-cells in response to glucose stimulations, intracellular insulin homeostasis in tilapia beta-cells generally does not require transcriptional activation of the insulin 1 gene and most likely relies on an enlarged intracellular insulin 1 mRNA pool. | en_US |
| dc.description | Thesis (Ph.D.)--Dalhousie University (Canada), 2007. | en_US |
| dc.language | eng | en_US |
| dc.publisher | Dalhousie University | en_US |
| dc.publisher | | en_US |
| dc.subject | Biology, Molecular. | en_US |
| dc.title | Molecular characterization of the insulin genes in Nile tilapia (Oreochromis niloticus). | en_US |
| dc.type | text | en_US |
| dc.contributor.degree | Ph.D. | en_US |
