Molecular mechanisms of the maintenance of stem cell systems

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To analyze the molecular mechanisms of the maintenance of stem cell immaturity and those of the cell differentiation in stem cell systems, we carried out the following research.1) Function of Akt signal in the maintenance of embryonic stem cellsNuclear reprogramming' can take place by cell fusion between somatic cells with mouse embryonic stem calls (ES cells). Activation of Akt signaling in ES cells significantly promoted the efficiency of the reprogramming. In addition, the cells obtained by the cell fusion acquired the pluripotency Them results clearly demonstrate that Akt signal can maintain the pluripotency of the cells. To the contrary, Akt signaling significantly reduced the efficiency of reprogramming after somatic nuclear transfer.2) Reprogramming of blood cell differentiation by the null mutation of GATA-1GATA-1 is an essential transcription factor for erythroid differentiation. In vitro differentiation from GATA-1 null ES cells to erythroid cells gave rim to the erythroid cells. And the erythroid nails mild proliferate for long term. These erythroid cells possessed the ability to differentiate to neutrophils and macrophages. In addition, epigenetic status of the GATA-1 null erythroid cells was quite different from its wild type counterpart. This result clearly demonstrate that this experimental system is an excellent model system to analyze the epigenetic modification by transcription factors.