Medical genetic research on molecular basis of epigenetic regulation and human diseases

该项目重点研究包括人类疾病在内的表观遗传基因调控及相关遗传现象，在DNA甲基转移酶（DNMT）、甲基化DNA结合蛋白（MBD蛋白）、染色质绝缘子、基因组印记以及小鼠生殖细胞和胚胎干细胞（ES细胞）分化等方面发现了大量新发现。 Sasaki博士的小组开发了DNMT3A和DNMT3B的生殖细胞特异性敲除小鼠，并报道这些小鼠是不育的，并且配子发生过程中DNMT3A介导的DNA甲基化是建立基因组印记所必需的。这一结果对印迹机制产生了很大影响。此外，对DNMT3A或其相关因子DNMT3L缺陷的突变小鼠的研究表明，其睾丸发生减数分裂畸变和转座子转录抑制，并且这些突变小鼠卵子衍生的胚胎具有异常胎盘，导致流产。此外，Sasaki 的小组研究了 CpG 二核苷酸在男性或女性生殖细胞特异性甲基化区域中的分布，并表明 DNMT3L 或相关因子可能与 ICF 综合征的发生有关。MBD1 充当 DNA 甲基化介导的转录抑制因子。 Nakao 的研究小组报告说，MBD1 招募组蛋白甲基转移酶 SETDB1 及其激活因子 MCAF1（含 MBD1 的染色质相关因子），导致转录抑制和异染色质形成，其标志是组蛋白 H3 的第 9 个赖氨酸三甲基化。在这种情况下，MBD1 的 SUMO 化对于形成 MBD1-MCAF1-SETDB1 抑制复合物非常重要。还发现 MBD1 和多梳蛋白在转录抑制和异染色质形成中具有重叠的作用。此外，另一种MBD蛋白MeCP2的MBD结构域在Rett综合征中经常发生突变，并且大多数MBD突变体失去了结合甲基化DNA的能力。 Nakao 小组发现，一些 MBD 突变体保留了甲基化 DNA 结合，这表明存在未知的机制来发展这种疾病。进一步地，在人类基因组的边界元件中，发现绝缘子结合蛋白CTCF与染色质重塑因子CHD8配合，产生对H191IGF2印迹区域的增强子阻断作用。这是绝缘子与表观遗传重塑相关的第一个证据。在小鼠ES细胞的神经分化过程中，发现PML体和染色中心发生了显着的重组，Oct3/4基因位点在ES细胞、神经前体细胞和终末分化神经元的各个阶段均存在组蛋白乙酰化和甲基化以及DNA甲基化的差异标记。较少的

The project focused on the investigations of epigenetic gene regulation and related genetic phenomena including human diseases, and discovered a lot of new findings on DNA methyltransferases (DNMT), methylated DNA binding proteins (MBD proteins), chromatin insulator, genomic imprinting, and differentiation of mouse germ cells and embryonic stem cells (ES cells). Dr. Sasaki's group developed germ cell-specific knockout mice for DNMT3A and DNMT3B, and reported that these mice were sterile, and that DNMT3A-mediated DNA methylation during gametogenesis is required for establishing genomic imprinting. This result had a great impact on the imprinting mechanisms. In addition, studies of mutant mice deficient for DNMT3A or its associated factor named DNMT3L showed that aberrations of meiosis and transcriptional repression of transposons occurred in their testis, and that embryos derived from eggs of these mutant mice had abnormal placenta, resulting in the miscarriage. Further, Sasaki's group … More studied the distribution of CpG dinucleotides in male or female germ cell-specific methylated regions, and showed that DNMT3L or related factors can be implicated in development of ICF syndrome.MBD1 functions as a DNA methylation-mediated transcriptional repressor. Nakao's group reported that MBD1 recruits histone methyltransferase SETDB1 and its activating factor MCAF1 (MBD1-containing chromatin associated factor), resulting ir transcriptional repression and heterochromatin formation that is marked with trimethylation of 9th lysine of histone H3. In this case, SUMOylation of MBD1 is important for forming the MBD1-MCAF1-SETDB1 repressive complexes. It was also found that MBD1 and polycomb group proteins have overlapping roles in transcriptional repression and heterochromatin formation. In addition, MBD domain of MeCP2, another type of MBD proteins, is frequently mutated in Rett syndrome, and most MBD mutants lost the ability to bind methylated DNAs. Nakao group found that some MBD mutants retained the methylated DNA binding, suggesting the presence of unidentified mechanisms to develop this disease. Further, in the boundary elements of human genome, insulator binding protein CTCF was found to cooperate with chromatin remodeling factor CHD8, resulting in the enhancer blocking effect on H191IGF2 imprinted region. This is a first evidence for insulator linked to epigenetic remodeling. In neural differentiation of mouse ES cells, PML bodies and chromocenters were found to be remarkably reorganized, and Oct3/4 gene locus was differentially marked with histone acetylation and methylation, and DNA methylation at each stage of ES cells, neural precursor cells and terminally differentiated neurons. Less