Molecular Genetic Analysis of Mouse Telomerase in vivo

다국어 초록 (Multilingual Abstract)

To examine the role of telomerase in normal and neoplastic growth, I have deleted the telomerase RNA component(mTR) from the mouse germline. mTR-/- mice lacked detectable telomerase activity yet were viable for the six generations analyzed. The role of telomerase was investigated in highly proliferative organs in successive generations of mTR-deficient mice. Late generation animals exhibited defective spermatogenesis with increased apoptosis and decreased proliferation in the testis. These progressive adverse effects coupled with telomere length reductions indicate that telomerase is essential for normal cellular homeostasis. We also studied a variety of physiological processes in an aging cohort of mTR-/- mice. Age-dependent telomere shortening and accompanying genetic instability were associated with shortened life span as well as a reduced capacity to respond to stresses such as wound healing and hematopoietic ablation. In addition, we found an increased incidence of spontaneous malignancies. These findings demonstrate a critical role for telomere length in the overall fitness, reserve, and well being of the aging organism.
Recently, c-myc has shown to induce transcription of telomerae reverse transcriptase(TERT) by binding directly to the 5'-promoter region of TERT. Since c-myc plays a role in cellular transformation and immortalization by heterodimerization with Max and Mxi-1 compete with c-myc by binding to Max, Mxi-1 is likely to control telomerase activity. In order to investigate the regulation of TERT, we have performed cDNA array using mouse embryonic fibroblast cells deficient for Mxi-1. We have found 10 different transcripts that were overexpressed in Mxi-1 null fibroblast from 588 cDNA array blot. Among those, Akt was the most highly expressed in Mxi-1 null MEFs. The overexpression of Akt transcript was confirmed by Realtime RT-PCR. Its protein expression exhibited induced in Mxi-1 null MEFs. We are currently further investigating the molecular mechanism by which telomerase is regulated through Mxi-1/Akt/Myc system. The further result in this study will be presented.