Chromatin-based regulation of neural stem cells

神经干细胞（NSCs）有望用于治疗各种神经系统疾病 常见于退伍军人，如创伤性脑损伤（TBI）和帕金森病。除了提供 虽然神经干细胞用于基于移植的治疗，但神经干细胞也是人类神经元和神经胶质细胞的重要来源， 药物发现和开发。为了实现NSC用于人类治疗的全部潜力，重要的是 了解调节特定神经细胞类型产生的分子机制。我们的长期 目的是了解神经干细胞产生特定类型神经元的细胞和分子机制 和胶质细胞。出生后和成年哺乳动物脑内的脑室-脑室下区（V-区）存在神经干细胞。 SVZ）。重要的是，V-SVZ神经干细胞保留了不同的区域特性，这些特性是产生不同神经干细胞的基础。 神经元亚型例如，腹侧V-SVZ中的NSC产生不同于那些神经元亚型的神经元亚型。 从背侧V-SVZ的神经干细胞中产生。此外，这种NSC区域身份在很大程度上是细胞固有的，我们 已经表明，神经干细胞通过连续的细胞分裂“记住”它们的区域身份。的表达 Nkx2.1定义了腹侧V-SVZ中的NSC群体。而音速刺猬（SHH）需要诱导 Nkx2.1在早期胚胎脑腹侧神经干细胞中的表达，我们的初步研究表明，SHH- 在腹侧V-SVZ神经干细胞中维持Nkx2.1表达不需要信号传导，这表明 这些细胞表观遗传地“记住”它们的区域身份。混合谱系白血病-1（Mll 1）编码一种 染色质调节子，是进化上保守的转录记忆系统的一部分，MLL 1是 正常V-SVZ神经发生所必需的。我们发现MLL 1蛋白在Nkx2.1调控元件处富集， 用条件性MLL 1缺失或MLL 1特异性化学抑制剂破坏MLL 1活性， 在腹侧V-SVZ神经干细胞中Nkx2.1表达的丧失。MLL 1抑制逆转后，Nkx2.1表达 仍然很低，但神经元的生产得到恢复。基于这些发现，我们的中心假设是， MLL 1需要通过特定的染色质状态变化来维持NSC区域身份。在这次更新中， 应用，我们建议调查MLL 1在NSC区域身份中的作用，并确定分子水平。 MLL 1维持区域特异性基因表达的机制。鉴于国家安全委员会的区域特性是一个 他们的神经原性潜力的关键方面，获得的结果将对我们的能力， 为人类转化研究和移植治疗生产特定类型的神经元。此外，委员会认为， 这些研究提出了关于神经干细胞区域特性的新的基本神经发育概念， 重要的是要了解人类MLL 1突变如何导致魏德曼-施泰纳综合征， 发育障碍，包括智力障碍和自闭症。最后，发现MLL 1依赖性 基因组调控元件的机制可能会引起更广泛领域的兴趣， 神经发育、表观遗传学和干细胞生物学。我们的初步研究，在V-SVZ和 染色质生物学，以及我们与亚伦迪亚兹博士（生物信息学创新和 #24453;，支持该项目的可行性。

Neural stem cells (NSCs) hold promise for the treatment of a wide range of neurological disorders common to Veterans such as traumatic brain injury (TBI) and Parkinson's disease. In addition to providing cells for transplantation-based therapies, NSCs are also an important source of human neurons and glia for drug discovery and development. To realize the full potential of NSCs for human therapy, it is important to understand the molecular mechanisms that regulate the production of specific neural cell types. Our long-term goal is to understand the cellular and molecular mechanisms by which NSCs produce specific types of neurons and glia. The postnatal and adult mammalian brain harbors NSCs in the ventricular-subventricular zone (V- SVZ). Importantly, V-SVZ NSCs retain distinct regional identities that underlie the production of different neuronal subtypes. For instance, NSCs in the ventral V-SVZ produce neuron subtypes different from those born from NSCs in the dorsal V-SVZ. Furthermore, such NSC regional identity is largely cell-intrinsic, and we have shown that NSCs “remember” their regional identity through serial cell divisions. The expression of Nkx2.1 defines a population of NSCs in the ventral V-SVZ. While sonic hedgehog (SHH) is required to induce Nkx2.1 expression in ventral NSCs of the early embryonic brain, our Preliminary Studies indicate that SHH- signaling is not required for the maintenance of Nkx2.1 expression in ventral V-SVZ NSCs, suggesting that these cells epigenetically “remember” their regional identity. Mixed lineage leukemia-1 (Mll1) encodes a chromatin regulator that is part of an evolutionarily conserved transcriptional memory system, and MLL1 is required for normal V-SVZ neurogenesis. We found MLL1 protein enriched at Nkx2.1 regulatory elements, and disruption of MLL1 activity with either conditional Mll1 deletion or an MLL1-specific chemical inhibitor resulted in the loss of Nkx2.1 expression in ventral V-SVZ NSCs. After reversal of MLL1 inhibition, Nkx2.1 expression remained low, but neuronal production was restored. Based on these findings, our central hypothesis is that MLL1 is required to maintain NSC regional identity via specific chromatin state changes. In this renewal application, we propose to investigate the role of MLL1 in NSC regional identity and determine the molecular mechanisms by which MLL1 maintains region-specific gene expression. Given that NSC regional identity is a critical aspect of their neurogenic potential, results obtained will have important implications for our ability to produce specific types of neurons for human translational research and transplantation therapies. Furthermore, these studies advance new basic, neurodevelopmental concepts regarding NSC regional identity, which may be important to understanding how mutations in human MLL1 cause Weidemann-Steiner Syndrome, a developmental disorder that includes intellectual disability and autism. Finally, discovering MLL1-dependent mechanisms at genomic regulatory elements will likely be of interest to the broader fields of neurodevelopment, epigenetics and stem cell biology. Our Preliminary Studies, expertise in V-SVZ and chromatin biology, and our productive collaborations with Dr. Aaron Diaz (for bioinformatics innovation and support), support the feasibility of this project.