碱基切除修复在体细胞诱导重编程中的作用和机制研究

It is critical for high quality iPSCs to maintain genomic instability during somatic cell reprogramming. The efficiency of DNA damage repair is closely linked to the genomic stability and integrity. Our previous studies have for the first time demonstrated that sequentially reprogrammed iPSCs could produce all-iPSC mice for up to six generations through serial tetraploid complementation. However, the viability of the all-iPSC mice decreased with accumulated point mutations. Therefore, combining with our previous results, we first aim to explore the regulation of base excision repair(BER) that the important pathway for DNA damage repair during the sequentially reprogramming system. Furthermore, after analysis on the BER efficiency during the whole reprogramming process, we will check and identify the candidate BER pathway genes associated with BER regulation. Meanwhile, the network of BER regulation in the reprogramming process will be revealed. Most importantly, we will investigate if the high efficiency BER could result in more high quality iPSCs. Overall, the present study can provide novel clues to understand the molecular mechanism of iPSC induction and improve the safety and efficiency for future clinical applications of iPSCs.

体细胞重编程过程中基因组的稳定性对得到高质量的iPS细胞至关重要，而DNA损伤修复效率对维持细胞基因组的稳定性又非常关键。我们前期研究中首次建立的体细胞连续六次诱导重编程体系发现随着每一代iPSC质量的逐渐降低，点突变呈现出逐渐积累的趋势(Gao Shuai et al. Nature Communications, 2015)。因此，我们将以碱基切除修复（BER）这一重要的DNA损伤修复通路为切入点，首先探讨连续六次诱导重编程中BER通路效率的变化和在其中的作用。其次，通过对整个体细胞重编程过程中BER效率变化规律的分析，以及进一步对BER通路相关基因的功能研究，来系统的阐明BER在iPS诱导过程中的作用和调控机制。最后，通过提高BER通路效率来揭示其与高质量的iPS细胞之间的关系。本项目将有助于加深对体细胞重编程的理解，并为促进临床上高质量的iPS细胞的获得具有重要的理论和实践意义。

基因组的稳定性对通过转录因子介导的体细胞重编程后得到高质量的iPS细胞至关重要，而维持基因组的稳定性又很大程度上依赖于DNA损伤修复效率。本项目以前期研究建立的体细胞连续六次诱导重编程体系为基础，以碱基切除修复（BER）通路为切入点，首先发现BER通路效率在连续重编程过程中随着点突变的积累而逐渐降低。进一步的研究表明，在重编程过程中提高BER效率可以显著增进体细胞重编程的效率，进而获得较高质量的iPS细胞。最后的机制研究发现，提高BER效率可以增加重编程早期的细胞增殖状态，并且在重编程的中后期也会促使更多的处于中间状态的pre-ipS向完全的iPS方向转化。本研究所取得的成果不仅会加深对体细胞重编程这一重要领域的理解和认识，也会为临床上高质量iPS细胞获得和应用提供重要的理论指导和依据。

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