碩士 / 國立臺灣海洋大學 / 生命科學暨生物科技學系 / 103 / Heme is a prosthetic group of hemoglobin responsible for binding oxygen molecules. However, the free form of heme produces free radicals which induce oxidative stress in normal cells. Therefore it needs to be removed through heme oxygenase (HO). The two kinds of homologous genes Ho1 and Ho2 have been found in mammals. Experiments in mice model reveal differences in tissue expression, gene regulation and biochemical characteristics between the two homologous genes. In addition to the metabolism of heme, the two homologous genes have been found related to iron balance and anti-oxidation reaction. Especially, Ho gene has also been confirmed to play an important role in embryo development, indicating a more complex physiological significance for the metabolism of heme.
Our laboratory has found ho homologs in the zebrafish genome, named ho1a, ho1b, ho2a and ho2b. Since zebrafish are more primitive vertebrates and possess the characteristics of in vitro fertilization, they are suitable for studying the evolution of functions of ho gene and their roles in embryonic development. In this study the in situ hybridization and Q-RT-PCR of four ho genes were first performed to analyze the expression pattens and expression levels of each individual gene in the embryo 24 to 120 hours post fertilization (hpf). The results showed ho1a and ho2b exhibited more obvious manifestations in the yolk sac and the central nervous system respectively during embryonic development. Since Ho1 expression is regulated by hypoxia in mammals, we tried to treat fertilized zebrafish egg in hypoxic conditions and observed an increase in ho1a gene expression in embryos. Then we focused on the promoter region of ho1a and determined the initiation start site by 5'RACE. We also cloned different fragments of the promoter region to assay their analysis. The results showed a possible hypoxia response element (HRE) site in -1141 to -1145 bp region of the promoter. This study showed the ho1 expression in the yolk sac and its hypoxia-inducible characteristics might already emerge in the early stage of vertebrate evolution, and it might be specific for heme metabolism. The interesting thing is that the functions of ho2 manifested in the central nervous system were responsible for not only heme metabolism but also active involvement in the development of the nerves.
| Identifer | oai:union.ndltd.org:TW/103NTOU5613034 |
| Date | January 2015 |
| Creators | Chen,Li-Will, 陳利維 |
| Contributors | Han-Jia Lin, 林翰佳 |
| Source Sets | National Digital Library of Theses and Dissertations in Taiwan |
| Language | zh-TW |
| Detected Language | English |
| Type | 學位論文 ; thesis |
| Format | 57 |
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