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

该项目主要研究表观遗传基因调控及相关遗传现象，包括人类疾病，并在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、小鼠生殖细胞和胚胎干细胞（ES细胞）分化等方面发现了许多新发现。Sasaki博士的小组开发了DNMT 3A和DNMT 3B的生殖细胞特异性敲除小鼠，并报告说这些小鼠是不育的，并且在配子发生期间DNMT 3A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的影响。此外，对缺乏DNMT 3A或其相关因子DNMT 3L的突变小鼠的研究表明，在其睾丸中发生减数分裂畸变和转座子的转录抑制，并且这些突变小鼠的卵衍生的胚胎具有异常胎盘，导致流产。此外，佐佐木的小组 关于我们 通过研究男性和女性生殖细胞特异性甲基化区域的CpG二核苷酸分布，发现DNMT 3L或相关因子可能参与ICF综合征的发生，MBD 1是DNA甲基化介导的转录抑制因子。Nakao的研究小组报道，MBD 1招募组蛋白甲基转移酶SETDB 1及其激活因子MCAF 1（含MBD 1的染色质相关因子），导致ir转录抑制和异染色质形成，以组蛋白H3的第9个赖氨酸的三甲基化为标志。在这种情况下，MBD 1的SUMO化对于形成MBD 1-MCAF 1-SETDB 1抑制复合物是重要的。研究还发现MBD 1和polycomb组蛋白在转录抑制和异染色质形成中具有重叠作用。此外，另一种MBD蛋白MeCP 2的MBD结构域在Rett综合征中频繁突变，并且大多数MBD突变体丧失了结合甲基化DNA的能力。Nakao研究组发现，一些MBD突变体保留了甲基化DNA结合，表明存在发生这种疾病的未知机制。在人类基因组的边界元件中，发现了绝缘子结合蛋白CTCF与染色质重塑因子CHD 8协同作用，导致对H191 IGF 2印迹区域的增强子阻断作用。这是绝缘体与表观遗传重塑有关的第一个证据。在小鼠ES细胞神经分化过程中，PML小体和染色中心发生了明显的重组，Oct 3/4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的差异，DNA甲基化也存在差异。少

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