published_or_final_version / abstract / Obstetrics and Gynaecology / Master / Master of Philosophy

Further investigation of possible regulatory pathway of NYD-SP24 demonstrated that the cell cycle of NYD-SP24 overexpressing cells was incompletely blocked at G2/M phase, and one of cell cycle-related genes, p21, shown to be an inducer of differentiation in different types of cell system, was found upregulated in a p53-independent manner, consistent with a role of NYD-SP24 in differentiation. (Abstract shortened by UMI.) / Spermatogenesis is a unique cell differentiation process consisting of three main phrases, namely mitosis, meiosis and postmeiosis. The differentiation of germ cells in the process involves distinct transcriptional programs, each under control of different transcription factor network. Many testis-specific transcription factors have been reported previously, however, few detailed studies have been done. This thesis describes the characterization and functional studies of a newly discovered testis-specific transcription factor, NYD-SP24, and the investigation of the possible regulatory pathway of NYD-SP24 in spermatogenesis. / The results demonstrated that in normal human tissues, NYD-SP24 was specifically and highly expressed in the testis but not in other somatic tissues, indicating its possible role in spermatogenesis. In the mouse model, mRNA and protein of NYD-SP24 mouse homolog gene (mNYD-SP24) were increased in the first wave of spermatogenesis. During the differentiation of germ cells, mNYD-SP24 mRNA and protein were confined to spermatocyte, round spermatid and spermatozoa. In hyperthermic mouse model, expression of mNYD-SP24 was decreased following the damage to germ cells by heat shock, but returned to normal level upon recovery of spermatogenesis. These results suggest the involvement of NYD-SP24 in spermatogenesis. / To identify the possible downstream targets of NYD-SP24, microarray and two-dimension gel technologies were performed in NYD-SP24 overexpressing cells and control cells. The results of microarray showed that 16 genes were upregulated and 4 genes were downregulated in NYD-SP24 overexpressing cells. In the two-dimension gel analysis, 12 protein spots were found to be altered significantly, with 8 increased and 4 decreased. Among these proteins, 3 were successfully identified by mass spectrometry. The nuclei localization in germ cells and the ability of NYD-SP24 to alter gene expression profile suggest that NYD-SP24 may be a testis-specific transcription factor, involved in gene regulation in spermatogenesis. / Zhu Hu. / "June 2005." / Adviser: Chan Hsiao Chang. / Source: Dissertation Abstracts International, Volume: 67-07, Section: B, page: 3607. / Thesis (Ph.D.)--Chinese University of Hong Kong, 2005. / Includes bibliographical references (p. 136-146). / 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. / Abstract in English and Chinese. / School code: 1307.

Development of specific DNA methylation patterns is required for normal spermatogenesis. DNA methyltransferases (DNMTs) use S-adenosylmethionine (SAM) produced in a pathway requiring 5,10-methylenetetrahydrofolate reductase (MTHFR). This thesis describes: testicular phenotype differences derived from Mthfr-deficiency in different mouse strains; the cellular Mthfr expression pattern during male germ cell development; and finally, changes to the DNA methylation of Mthfr-deficient sperm. Mthfr-deficient BALB/c, but not C57BL/6, mice have reduced neonatal germ cell proliferation but both have abnormal germ cells as adults. Germ cell MTHFR expression differed developmentally in parallel with DNMTs associated with de novo methylation. Sperm from mice with reduced Mthfr levels or dietary folate deficiency had differential DNA methylation at multiple loci, compared to wildtype mice, indicating that maintenance as well as acquisition of methylation can be altered by SAM-reduction. These results highlight the important role of folate in sperm development throughout life.

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