近来研究表明在分化的体细胞中过表达几个在胚胎干细胞中高表达的转录因子就可以将体细胞重编程为诱导多能干细胞（iPS细胞）。iPS细胞在再生医学领域具有巨大的应用前景，用来模拟疾病的发生，进行药物筛选，甚至可以用于细胞治疗。同时，iPS细胞也为我们提供了一个非常好的工具用来研究细胞命运改变的表观遗传机制。我们实验室近年来在iPS细胞领域获得了重要进展，我们已经利用Dox诱导系统建立了两类连续重编程体系，可以保证重编程起始细胞的均一性。在第一种连续重编程体系中我们用了传统的OSKM四因子，通过四倍体囊胚互补实验获得六代重编程iPS小鼠，另外，我们还建立了用3*Flag标记的Oct4制备的OSKM iPS细胞及小鼠，这样我们就可以非常精细的研究外源Oct4在重编程过程中的作用机制。我们近来的研究发现DNA羟甲基化酶Tet1可以替代Oct4完成重编程。我们将利用这两个体系研究重编程的表观遗传机制。

Differentiated somatic cells can be reprogrammed to induced pluripotent stem cells (iPSCs) through overexpression of defined transcription factors that are highly expressed in embryonic stem cells (ESCs). iPSCs hold great promise to be used for diseases modeling, drug screening and cell transplantation based regenerative medicine. Meanwhile, the fundamental molecular mechanism underlying reprogramming deserves to be unravelled. We have established two sequential reprogramming systems based on doxycycline inducible system. In the first system, we have produced inducible iPSCs using the traditional four transcription factors(Oct4, Sox2, Klf4, c-Myc) and subsequently all-iPS mice were produced from these iPSCs through tetraploid complementation. At present, we have produced all-iPS mice to six generations. Furthermore, we have produced all-iPS mice in which the exogenous Oct4 was labeled with 3*Flag tag, which allows us to dissect the precise role of Oct4 in reprogramming. More recently, we have produced a second sequential reprogramming system in which the Oct4 was replaced by recently discovered DNA dioxygenase Tet1. In this specific project, we are planning to investigate the epigenetic mechanism of reprogramming involved in these two systems. DNA modifications, DNA damage and histone modifications will be investigated by using these two systems.