CTCF-dependent mechanisms of ATRX in neuronal differentiation

项目摘要 ATRX是ATRX综合征中突变的表观遗传因子。需要ATRX来维护 多能神经祖细胞（NPC），特别是当这些细胞启动脑中的分化程序时。 导致ATRX综合征的突变集中在两个区域：ATRX PHD指状结构域和ATRX PHD指状结构域。 解旋酶结构域。它们分别介导与组蛋白的相互作用和重塑染色质。有趣的是， PHD手指的突变与严重的智力残疾和精神障碍有关， 解旋酶结构域的突变通常表现为轻度的神经发育迟缓，但更严重的是生殖系统发育迟缓。 反常现象13.这种基因型-表型相关性的基础从未被研究过。ATRX有很好的- 在正常大脑发育的分子过程中发挥着重要作用，包括组蛋白变体 H3.3沉积和Polycomb阻遏复合物2靶向表观遗传沉默。它也有一个很差的 CTCF是一种重要的基因组结构蛋白，对发育至关重要。我们 初步数据表明ATRX的PHD指和解旋酶突变差异调节CTCF定位 并且可能是基因型-表型相关性的基础。我们的初步数据已经揭示了一个基因组范围的作用， CTCF定位中的ATRX。我们发现ATRX敲低（KD）小鼠胚胎干细胞（mESCs） 导致CTCF在许多基因组位点（包括印迹和非印迹基因座）积累。我们也 发现ATRX与ADNP和DNMT 3L相互作用，两者都可以阻止CTCF结合。使用 通过CRISPR/Cas9，我们已经产生了其中内源性Atrx等位基因已经被点CRISPR/Cas9替代的等基因ESC。 ATRX综合征患者中发现的突变体。我们发现PHD手指的突变导致了显著的 NPC分化受损，而解旋酶结构域的突变导致更微妙的分化 延误了.我们的初步发现和新的试剂使我们能够独特地询问ATRX的后果。 突变，通过CTCF进行基因组组织，以及ESC分化为NPC的能力。 基于我们的初步数据，我们建议测试不同的ATRX结构域调节特定的 不同程度地影响CTCF功能的染色质过程。在目标1中，我们将研究 ATRX综合征突变对基因表达和基因组组织的影响 分化在目标2中，我们将破译ATRX调节CTCF定位的机制。

PROJECT SUMMARY ATRX is an epigenetic factor that is mutated in ATRX syndrome. ATRX is required for the maintenance of multipotent neuroprogenitor cells (NPCs), particularly as these cells initiate differentiation programs in the brain. Mutations that cause ATRX syndrome cluster within two domains: the ATRX PHD finger domain, and the helicase domain. These mediate interactions with histones, and remodel chromatin, respectively. Interestingly, mutations in the PHD finger are associated with severe intellectual disability and psychomotor impairment, while mutations in the helicase domain often manifest with milder neurodevelopmental delays but more severe genital abnormalities13. The basis for this genotype-phenotype correlation has never been investigated. ATRX has well- established roles in molecular processes that are crucial for normal brain development including histone variant H3.3 deposition and Polycomb repressive complex 2 targeting for epigenetic silencing. It also has a poorly understood role in regulating CTCF, a critical genome architectural protein that is essential for development. Our preliminary data indicate PHD finger and helicase mutations of ATRX differentially regulate CTCF localization and may underlie genotype-phenotype correlations. Our preliminary data has uncovered a genome-wide role for ATRX in CTCF localization. We found that ATRX knock down (KD) in mouse embryonic stem cells (mESCs) results in CTCF accumulation at many genomic sites, including both imprinted and non-imprinted loci. We also discovered that ATRX interacts with ADNP and DNMT3L, both of which can prevent CTCF binding. Using CRISPR/Cas9, we have generated isogenic ESCs where the endogenous Atrx allele has been replaced by point mutants found in ATRX syndrome patients. We show that mutations in the PHD finger cause significant impairment of NPC differentiation, while mutations in the helicase domain cause more subtle differentiation delays. Our preliminary findings and novel reagents uniquely position us to interrogate the consequence of ATRX mutations, both for genome organization through CTCF, and for the ability of ESCs to differentiate into NPCs. Based on our preliminary data, we propose to test the hypothesis that distinct ATRX domains regulate specific chromatin processes that impinge to different extents on the function of CTCF. In Aim 1, we will investigate the consequence of ATRX syndrome mutations to gene expression and genome organization during neuronal differentiation. In Aim 2, we will decipher the mechanisms by which ATRX regulates CTCF localization.