| Budget Amount *help |
¥95,200,000 (Direct Cost: ¥95,200,000)
Fiscal Year 2012: ¥20,700,000 (Direct Cost: ¥20,700,000)
Fiscal Year 2011: ¥20,700,000 (Direct Cost: ¥20,700,000)
Fiscal Year 2010: ¥20,700,000 (Direct Cost: ¥20,700,000)
Fiscal Year 2009: ¥20,700,000 (Direct Cost: ¥20,700,000)
Fiscal Year 2008: ¥12,400,000 (Direct Cost: ¥12,400,000)
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| Research Abstract |
The purpose of this study is to understand the mechanism of quality control of spermatogonial stem cells. In our previous grant on priority area, we reported a long-term culture system for spermatogonial stem cells, which were designated as germline stem (GS) cells. We used GS cells to produce knockout animals by homologous recombination in these cells.
In the course of this study, we noticed that GS cells are very stable in their genetic and epigenetic properties. Unlike mbryonic stem (ES) cells that change their chromosome number and DNA methylation patterns in imprinted genes, GS cells maintained normal chromosome number and androgenetic DNA methylation patterns in imprinted genes for more than 2 years in vitro. Based on this observation, we hypothesized that GS cells have a unique mechanism to prevent germine transmission of genetic and epigenetic abnormalities to subsequent generations and that defects in these properties will lead to pluripotent cell derivation or abnormalities in spermatogenesis.
In the current grant, we were able to establish GS cells from fetal germ cells, which had defects in histone modification patterns in imprited genes. Offspring that were derived from these cells showed abnormal DNA methylation patterns in imprinted genes, which continued at least five generations. We also analyzed the impact of Dnmt genes or oncogenes in genetic and epigenetic properties of GS cells. Our analysis revealed that p53 is important in genetic integrity of GS cells and that DNMT3a/b are responsible for maintaining epigenetic integrity. We also established the first experimental system for in vitro tranformation of germ cells, which will be useful for understanding the mechanism of epigenetic regulation in SSCs.
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