The development of a functional vascular system is impinged upon the restructuring of a primitive vasculature into a more complex and mature vessel network via a process known as angiogenesis. Of particular importance to this vascular remodeling process is the function of the Tek/Tie-2 receptor tyrosine kinase. Mouse gene-targeting studies have shown that Tie-2 deficient embryos succumb to embryonic death at embryonic day 9.5 due to insufficient sprouting and remodeling of the primary capillary plexus. Over the years, the functions and the signaling pathways downstream of Tie-2 receptor have been elucidated; however, the repertoire of genes controlled by Tie-2 signaling leading to angiogenesis had not been studied. To identify the underlying genetic mechanisms, transcriptomes from Tie-2 wild-type (WT) and knockout (KO) embryonic day 8.5 yolk sac tissues were quantitatively analyzed using a gene expression profiling technique called Serial Analysis of Gene Expression (SAGE). Tie-2 WT and KO SAGE libraries were constructed, sequenced and compared to identify genes that were differentially expressed. A list of candidate genes was selected for further validation using semi-quantitative PCR that included 4933402E13Rik, a novel transcript encoding a protein product containing the melanoma-associated antigen (MAGE) domain. Initial characterization of 4933402E13Rik suggested a murine-specific expression profile restricted to the yolk sac, embryo, placenta, testis, endothelial and embryonic stem cells. The expression of 4933402E13Rik in mouse endothelial cells was found to be regulated by Tie-2 signaling since down-regulation of Tie-2 level via siRNA knockdown resulted in decreased 4933402E13Rik mRNA expression. In contrast, stimulation of Tie-2 in mouse endothelial cells using its ligand, Angiopoietin-1, increased 4933402E13Rik mRNA levels. Additionally, 4933402E13Rik expression was found to be modulated through epigenetics especially by histone deacetylation. Mouse endothelial cells treated with Trichostatin A, a potent inhibitor of histone deacetylase, led to an increase in the expression of 4933402E13Rik. Taken together, the results of this study shed new insight on the repertoire of genes implicated in Tie-2 signaling. The identification of 4933402E13Rik as a novel gene modulated by Tie-2 provides a new avenue of research on Tie-2 signaling that may contribute further to our understanding of vascular development.
| Identifer | oai:union.ndltd.org:TORONTO/oai:tspace.library.utoronto.ca:1807/24704 |
| Date | 05 August 2010 |
| Creators | Chen, Stephen Huang-Ting |
| Contributors | Dumont, Daniel Joseph |
| Source Sets | University of Toronto |
| Language | en_ca |
| Detected Language | English |
| Type | Thesis |
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