Although much more work needs to be done to elucidate the functional roles of FSH and LH in fish reproduction, the preset study provides a relatively comprehensive study for us to understand the potential roles of FSH and LH during ovarian development in fish, especially the importance of FSH. / At the same time, functional studies were carried out to examine and compare bioactivities of the CHO-derived zfFSH and zfLH in zebrafish ovary, which is the major part of the present project. The following aspects were covered to investigate the actions of zfFSH and zfLH: steroidogenesis and folliculogenesis. / Both recombinant zfGTHs stimulated activin betaA expression but slightly suppressed activin betaB expression. During short-term treatment, zfFSH and zfLH exhibited similar stimulatory effects on activin betaA expression; the effect of zfLH became more prominent after 24 h treatment while zfFSH had little effect. / Previously, our laboratory had established two stable Chinese hamster ovary (CHO) cell lines expressing recombinant zebrafish FSH (zfFSH) and LH (zfLH). However, the production yields are very low. Therefore, the present study tried to adopt the yeast Pichia pastoris as another bioreactor to produce recombinant zfFSH and zfLH. Two different forms of expression vectors for a native form and a fusion form carrying a His-tag, respectively, were constructed for each hormone. Their bioactivities were monitored and confirmed by receptor-based reporter gene assays as well as ovarian fragment incubation. As expected, the native form exhibited much higher activities than the fusion form. / The pituitary gonadotropins (GTHs), follicle-stimulating hormone (FSH) and luteinizing hormone (LH), are the key hormones controlling vertebrate reproduction. Although the two gonadotropins have been characterized in numerous teleost species, our understanding of their biological functions remains rather limited. This is largely due to the lack of pure form of homologous gonadotropins and inadequate understanding of gonadal physiology in most species studied as well as species variation of hormone actions. The present study aims at systematically investigating the functional roles of FSH and LH in the ovary using zebrafish as the model. Zebrafish is becoming more and more popular as the model of reproductive and developmental studies due to several advantages. First, though its body size is small, its ovary is relatively large and available all the year around. Second, zebrafish spawns everyday and its development is fast. Last but not least, its bioinformatics information is tremendous compared to other fish models. / We investigated the effects of zfFSH and zfLH on steroidogenesis by examining the regulation of aromatase by these two hormones. Aromatase catalyzes the conversion of androgens into estrogens during steroidogenesis. Both recombinant zfGTHs stimulated the aromatase expression during short-term treatment (8 h) in ovarian fragment culture, with zfFSH much more potent than zfLH. However, zfFSH continued to exhibit powerful effect on aromatase expression after 24 h treatment while zfLH had little effect at all. The stimulatory effect of zfFSH on aromatase expression was time-, dose- and stage-dependent and was also confirmed by in vivo study. Furthermore, it was also zfFSH but not zfLH that significantly stimulated StAR protein expression during short-term treatment. StAR protein is critical to steroidogenesis by facilitating the movement of cholesterol across the mitochondrial membrane. / zfLH was found to be able to induce GVBD in zebrafish, as demonstrated in other fish species. However, our preliminary data showed that zfFSH was also involved in this process. To our knowledge, this is the first time to demonstrate that homologous FSH induces GVBD in teleosts. / Yu, Xiaobin. / Adviser: Wei Ge. / Source: Dissertation Abstracts International, Volume: 70-09, Section: B, page: . / Thesis submitted in: December 2008. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2009. / Includes bibliographical references (leaves 152-181). / Electronic reproduction. Hong Kong : Chinese University of Hong Kong, [2012] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Electronic reproduction. [Ann Arbor, MI] : ProQuest Information and Learning, [200-] System requirements: Adobe Acrobat Reader. Available via World Wide Web. / Abstracts in English and Chinese. / School code: 1307.
| Identifer | oai:union.ndltd.org:cuhk.edu.hk/oai:cuhk-dr:cuhk_344412 |
| Date | January 2009 |
| Contributors | Yu, Xiaobin., Chinese University of Hong Kong Graduate School. Division of Biology. |
| Source Sets | The Chinese University of Hong Kong |
| Language | English, Chinese |
| Detected Language | English |
| Type | Text, theses |
| Format | electronic resource, microform, microfiche, 1 online resource (xviii, 181 leaves : ill.) |
| Rights | Use of this resource is governed by the terms and conditions of the Creative Commons “Attribution-NonCommercial-NoDerivatives 4.0 International” License (http://creativecommons.org/licenses/by-nc-nd/4.0/) |
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