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.

Indiana University-Purdue University Indianapolis (IUPUI) / Phosphatases of regenerating liver, consisting of PRL-1, PRL-2 and PRL-3, belong to a novel protein tyrosine phosphatases subfamily, whose overexpression promotes cell proliferation, migration and invasion and contributes to tumorigenesis and metastasis. However, although great efforts have been made to uncover the biological function of PRLs, limited knowledge is available on the underlying mechanism of PRLs’ actions, therapeutic value by targeting PRLs, as well as the physiological function of PRLs in vivo. To answer these questions, we first screened a phage display library and identified p115 RhoGAP as a novel PRL-1 binding partner. Mechanistically, we demonstrated that PRL-1 activates RhoA and ERK1/2 by decreasing the association between active RhoA with GAP domain of p115 RhoGAP, and displacing MEKK1 from the SH3 domain of p115 RhoGAP, respectively, leading to enhanced cell proliferation and migration. Secondly, structure-based virtual screening was employed to discover small molecule inhibitors blocking PRL-1 trimer formation which has been suggested to play an important role for PRL-1 mediated oncogenesis. We identified Cmpd-43 as a novel PRL-1 trimer disruptor. Structural study demonstrated the binding mode of PRL-1 with the trimer disruptor. Most importantly, cellular data revealed that Cmpd-43 inhibited PRL-1 induced cell proliferation and migration in breast cancer cell line MDA-MB-231 and lung cancer cell line H1299. Finally, in order to investigate the physiological function of PRLs, we generated mouse knockout models for Prl-1, Prl-2 and Prl-3. Although mice deficient for Prl-1 and Prl-3 were normally developed, Prl-2-null mice displayed growth retardation, impaired male reproductive ability and insufficient hematopoiesis. To further investigate the in vivo function of Prl-1, we generated Prl-1-/-/Prl-2+/- and Prl-1+/-/Prl-2-/- mice. Similar to Prl-2 deficient male mice, Prl-1-/-/Prl-2+/- males also have impaired spermatogenesis and reproductivity. More strikingly, Prl-1+/-/Prl-2-/- mice are completely infertile, suggesting that, in addition to PRL-2, PRL-1 also plays an important role in maintaining normal testis function. In summary, these studies demonstrated for the first time that PRL-1 activates ERK1/2 and RhoA through the novel interaction with p115 RhoGAP, targeting PRL-1 trimer interface is a novel anti-cancer therapeutic treatment and both PRL-1 and PRL-2 contribute to spermatogenesis and male mice reproductivity.