Application of Transgenic Mice Models in Functional Study of Two Putative Oncogenes: Alc-1 and Eif5a2

This dissertation, "Application of Transgenic Mice Models in Functional Study of Two Putative Oncogenes: ALC-1 and EIF5A2" by Muhan, Chen, 陳牧唅, was obtained from The University of Hong Kong (Pokfulam, Hong Kong) and is being sold pursuant to Creative Commons: Attribution 3.0 Hong Kong License. The content of this dissertation has not been altered in any way. We have altered the formatting in order to facilitate the ease of printing and reading of the dissertation. All rights not granted by the above license are retained by the author. Abstract: ABSTRACT Chen Muhan Abstract of thesis entitled APPLICATION OF TRANSGENIC MICE MODELS IN FUNCTIONAL STUDY OF TWO PUTATIVE ONCOGENES: ALC-1 AND EIF5A2 Submitted by Chen Muhan For the degree of Doctor of Philosophy at the University of Hong Kong In February, 2007 DNA sequence amplification and subsequent overexpression of oncogene within the amplicon has been shown to play an important role in the pathogenesis and progression of various solid tumors, probably because overexpression of the amplified target gene confers a selective advantage. Therefore, isolation and characterization of oncogenes from frequently amplified region is imperative to understand the molecular mechanism of tumorigenesis. Amplification of the long arm of chromosome 1 with a minimal amplified region at 1q21 is the most frequently detected alteration in 58-78% hepatocellular carcinoma (HCC). Similarly, amplification of 3q26 has been frequently detected in several cancers including ovarian cancer. These suggest that these regions may harbor candidate oncogenes associated with tumorigenesis. Recently, two novel candidate oncogenes, ALC-1 (amplification in liver cancer-1) and eIF5A2 (eukaryotic translation initiation factor 5A2), have been isolated from 1q21 and 3q26 in our laboratory, respectively. Previous in vitro studies have demonstrated the oncogenic roles of ALC-1 and eIF5A2 played in cancer development. However, the in vivo functions of these genes in development and tumor pathogenesis are still unclear. In ii ABSTRACT Chen Muhan this study, transgenic mice models of ALC-1 and eIF5A2 are generated and their in vivo functions are characterized. Four independent ALC-1 transgenic founders were obtained and two of them were used for in vivo functional studies. The results strongly supported that ALC-1 plays an important role in tumor pathogenesis including: 1) to cause spontaneous tumor formation in transgenic mice; and 2) to dramatically shorten the latency of tumor formation by alcohol intoxication. The possible molecular mechanism is that overexpression of ALC-1 can up-regulate cyclin D1, D3/CDK6 expression and down-regulate p27 expression, which promotes G1/S transition. This was further supported by the results of FACS analysis, which showed that overexpression of ALC-1 tend to keep MEFs in cell cycling. In addition, DNA synthesis was accelerated in hepatocytes of transgenic mice comparing to their wild-type siblings during liver regeneration after partial hepatectomy. However, ALC-1 overexpression had minor effects on mouse development. In the second part of the thesis, three independent eIF5A2 transgenic founders were obtained and two of them were further studied. EIF5A2 overexpression led to pre- mature aging phenotypes in transgenic mice, with the typical syndromes of shortened longevity, kyphosis, reduced body weight and size and delay of wound healing etc. Two interesting findings revealed the mechanism of eIF5A2 implicated in aging-inducing process. The first one is the increase of chromosomal instability in transgenic mice characterized with numerical chromosome changes, which might be caused by errors in chromosome segregation during the mitosis. Because higher frequencies of micronuclei, misaligned and lagging chromosome were detected in iii ABSTRACT Chen Muhan eIF5A2 transgenic mice compared to