DNA甲基化通过调节基因表达控制诸多生命活动过程。DNA甲基化谱式的建立涉及DNA去甲基化和起始性甲基化。以主动去甲基化为特征的、发生于胚胎发育早期和生殖细胞发生过程中的表观遗传重编程分子机理是一个尚未解决的重大问题。由于此类重编程过程发生于难以用常规分子生物学手段进行研究的特殊发育时期，对于DNA去甲基化机理的探索一直进展不大。然而在过去的两年中，包括申请人实验室在内的几个研究组发现去甲基化有可能通过Tet双加氧酶介导的甲基胞嘧啶（5mC）的氧化来实现。目前验证这一假说的关键是要找到去除5mC氧化产物-羧基胞嘧啶(5caC)的生化途径。我们拟在业已建立的5caC 调节蛋白筛选与鉴定平台的基础上，对候选蛋白进行深入的生化和遗传学分析，在早期胚胎和生殖细胞中检验其生物学意义。具体目标是鉴定参与调节5mC氧化产物的蛋白因子，阐明其在DNA去甲基化过程中的作用，明确DNA去甲基化的分子机制。

DNA methylation regulates gene expression in multiple biological processes. Formation of genomic methylation patterns is determined by two opposing events, de novo methylation and demethylation. It is well known that genome-wide demethylation occurs in the early embryo and primordial germ cells. But important questions about demethylation mechanism remain unanswered, partly due to the fact that the developmental stages of DNA demethylation is not easily accessible for conventional molecular biology approaches. In the past years, several labs including ours revealed that DNA demethylation may take place through Tet dioxygenase-mediated oxidation of 5-methylcytosine. The crucial proof of this proposed pathway has to be provided by identifying factors that can actively remove the oxidation product - 5-carboxylcytosine from DNA. In our preliminary work, we have found a few candidate proteins which can reduce 5caC when expressed in transfected cells. The proposed study will focus on biochemical characterization and functional confirmation of these factors during early embryo development and germ cell formation in mice. Identification of factors that regulate or remove the 5mC oxidation derivation will contribute to understanding of the mechanism of DNA demethylation.