体细胞重编程不仅是细胞生物学的一个里程碑，而且在疾病模拟和细胞治疗领域具有重大应用价值。但在全面应用前尚需要克服一系列重要障碍（例如基因组和表观遗传学异常）。因此，深入理解重编程发生的机制非常关键。然而经典的重编程技术耗时长、效率低。本项目中以双方在重编程领域都处于国际领先，最近他们分别发现了一系列抑制性因子，包括以方发现的Mbd3和中方发现的NCoR/SMRT。抑制这些因子的表达可以极大提高效率（接近100%）并加速重编程进程（5－8天）。中以双方将通力合作阐述并比较这些抑制因子如何抑制重编程的机理，探索建立高效重编程的方法，力争将其效率提高到类似体细胞核移植的水平（仅仅经历1－2个细胞分裂并在24小时内完成 ）。同时本项目将通过高通量筛选鉴定能够替代敲除或敲降这些抑制因子的化合物，从而不仅可以用来提高小鼠化合物重编程，而且将尝试实现不含基因组以及表观遗传学异常的人化合物重编程。

The reprogramming of somatic cells to induced pluripotent stem cells (iPSCs) represents a milestone in cell biology and is full of practical implications, including disease modeling and cell-based therapies. Yet, a series of caveats (e.g., genomic and epigenomic alterations) need to be overcome to fulfill this promise. Understanding the mechanisms of reprogramming is fundamental in order to improve the methodology and eliminate these caveats, but the length and inefficiency of standard approaches have been serious obstacles. Several groups worldwide have isolated specific reprogramming populations to overcome this issue, but this approach falls short due the need of multiple time points of analysis and variables. The Israeli and Chinese groups are world leaders in mechanistic studies of somatic cell reprogramming. Besides seminal work on several other aspects, they have recently identified a series of repressors (including Mbd3 discovered by the Israeli group, and NCoR/SMRT by the Chinese group) that bind to the exogenously delivered reprogramming factors restraining their function. Reducing the expression of these repressors has a profound effect in enhancing (to a point of close to 100% efficiency) and accelerating (to 5-8 days) reprogramming. The 2 teams will combine efforts to characterize and compare how these repressors derail reprogramming. This approach could potentially result in further clues that allow reprogramming to be completed in 24 hours and with very few cell divisions, as it is indeed the case of reprogramming by somatic cell nuclear transfer. They will also perform high throughput screening for identifying small molecules that can substitute for knockout or RNAi approaches. These inhibitors will be employed to improve the efficiency of mouse chemical reprogramming, to achieve human chemical reprogramming, and to produce human iPSCs that are devoid of genomic hotspots displaying epigenetic aberrations.

体细胞重编程是一个多步骤，低概率的细胞命运转换事件。在这个过程中，细胞内的染色质状态和基因表达要经历巨大的变化。而这些变化，是由过表达的四个Yamanaka因子，即SOX2， KLF4， OCT4和c-MYC来共同启动的。这些转录因子可以招募表观调节因子，将其靶定到基因组，从而对基因组的修饰和基因的表达实施调控。目前关于多能性基因难以有效激活的表观调控机制尚未完全阐明，c-MYC导致不完全重编程细胞产生的原因也仍待探索。我们发现，在重编程过程中，SOX2， KLF4，OCT4和c-MYC，尤其是c-MYC可以将共抑制复合物NCoR/SMRT-HDAC3招募到基因组。该复合物的酶活性中心，HDAC3则对靶位点的组蛋白乙酰化修饰进行调节，降低其乙酰化水平，抑制基因的表达。在重编程前期，NCoR/SMRT-HDAC3复合物被招募到基因组，促进高表达的体细胞基因沉默，有利于重编程；而在重编程后期，NCoR/SMRT-HDAC3复合物被招募到多能性基因位点，抑制多能性基因的有效激活，阻碍重编程。干扰NCoR/SMRT-HDAC3复合物的功能会显著地提高重编程效率，说明该复合物对多能性基因的抑制作用是重编程的主要障碍之一。通过该研究，我们揭示了NCoR/SMRT共抑制蛋白家族和HDAC3在重编程过程中对基因表达的抑制作用,也揭示了c-MYC在重编程前期和后期的不同功能，至少在很大程度上解释了为什么c-MYC的存在会导致更多的不完全重编程细胞即pre-iPSCs、组蛋白去乙酰化酶抑制剂如VPA和Butyrate在四因子的条件下能发挥更为明显的功能。同时，该研究对于c-MYC和NCoR/SMRT-HDAC3在其他体系如癌症和发育中的作用机制提出了新的可能性。