Chromatin-based regulation of neural stem cells

神经干细胞(NSCs)有望治疗多种神经疾病 常见于退伍军人，如创伤性脑损伤(TBI)和帕金森氏症。除了提供 对于以移植为基础的治疗来说，神经干细胞也是人类神经元和胶质细胞的重要来源 药物发现和开发。为了实现神经干细胞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。我们的长期合作 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。 还有神经胶质细胞。出生后和成年哺乳动物的脑中，神经干细胞位于脑室-脑室下区(V- SVZ)。重要的是，V-SVZ NSC保留了独特的地区身份，这是不同 神经元亚型。例如，腹侧V-SVZ中的神经干细胞产生的神经元亚型与 出生于V-SVZ背侧的神经干细胞。此外，这种NSC地区认同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”他们的区域身份。的表达方式 Nkx2.1定义了腹侧V-SVZ内的神经干细胞种群。而需要音速刺猬(SHH)才能诱导 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-2. 在腹侧V-SVZ神经干细胞中，Nkx2.1的表达不需要信号转导，提示 这些细胞在表观遗传学上“记住”它们的区域身份。混合血统白血病-1(MLL1)编码一个 染色质调节器，是进化保守的转录记忆系统的一部分，而MLL1是 正常的V-SVZ神经发生所必需的。我们发现MLL1蛋白富含在Nkx2.1调控元件上，并且 通过条件ML1缺失或MLL1特异性化学抑制物导致MLL1活性中断 在腹侧V-SVZ神经干细胞中Nkx2.1的表达缺失。逆转MLL1抑制后，Nkx2.1的表达 维持在低水平，但神经元的产生有所恢复。基于这些发现，我们的中心假设是 MLL1需要通过特定的染色质状态变化来维持NSC的区域特性。在这次更新中 应用，我们建议研究MLL1在NSC区域识别中的作用，并确定分子 MLL1维持区域特异性基因表达的机制。鉴于NSC的地区认同是一种 他们的神经性潜能的关键方面，所获得的结果将对我们的能力有重要的影响 为人类的翻译研究和移植治疗产生特定类型的神经元。此外， 这些研究提出了关于NSC区域认同的新的基本神经发育概念，这可能 对了解人类MLL1突变如何导致魏德曼-斯泰纳综合征非常重要 包括智力残疾和自闭症在内的发育障碍。最后，发现MLL1依赖 基因组调控元件的机制可能会引起更广泛的领域的兴趣 神经发育、表观遗传学和干细胞生物学。我们的初步研究，V-SVZ的专业知识和 染色质生物学，以及我们与Aaron Diaz博士的富有成效的合作(用于生物信息学创新和 支持)，支持这个项目的可行性。

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.