Mechanisms of cytokinesis and delamination in the cerebral cortices

 描述(申请人提供)：神经元和神经胶质细胞是成熟大脑的运作单位，主要来自胚胎发育期间的神经干细胞(NSCs)。在大脑皮层产生神经元和神经胶质的神经干细胞对哺乳动物特别重要，因为它们最终会产生允许我们执行高级认知任务的组织。许多神经发育障碍是由涉及各种神经干细胞功能的分子和细胞机制的异常引起的。例如，新神经元的生成和迁移严重中断可能会导致小头畸形和无脑，而较轻微的发育缺陷可能会导致神经元连接的不完善，例如在自闭症和精神分裂症中变得明显的那些。调节皮质发育的分子和细胞信号的发育时间特别重要，因为时间上不同的侮辱可能会以不同的方式影响皮质、大脑活动和行为。许多缺陷与影响神经干细胞胞质分裂的机制有关，是不同疾病的基础。因此，了解干细胞是如何分裂的，以及在大脑发育和NSC成熟过程中，是什么控制了它们分裂的变化，对于理解神经发育障碍至关重要。在皮质发育过程中，神经干细胞必须在其细胞分裂中保持极其重要的平衡。他们必须首先通过对称分裂来扩大自己的人才库，然后他们必须改变他们的分裂方式，这样他们才能通过不对称分裂产生神经元和胶质细胞。目前对调节这些重要分裂的细胞和分子机制的了解仍然是支离破碎的，关于这一过程的主要调节因子仍有许多有待发现。我们最近发现了这一过程的一个新的调节因子，属于锌指特异蛋白家族 转录因子，称为Sp2。当我们仅在发育中的大脑皮层的神经干细胞中删除Sp2基因时，我们发现干细胞的积累以神经发生为代价。相比之下，Sp2的过度表达会迅速推动干细胞从发育中的皮层脑室表面的上皮细胞中剥离，并早熟地产生皮质神经元。我们已经发现了一些有趣的细胞生物学主题，这些主题是Sp2对神经干细胞的强大作用的基础，我们在初步数据中介绍了这些主题。根据这些发现，我们建议结合使用最先进的遗传小鼠品系、细胞和切片培养分析、实时成像协议、生化分析以及依赖Sp2的RNA和蛋白质景观图来测试中心假设，即Sp2依赖的转录通过调节发育中的大脑皮层中NSCs的对称和不对称分裂来调节增殖和分化的正确平衡。我们提供的初步证据表明，Sp2可能通过其相互作用在神经干细胞中执行这一关键功能 具有已知的细胞分裂机制和途径。因此，我们的研究建议探索一种新的机制模型，将驱动胞质分裂的分子机制与不对称分裂的神经干细胞在大脑皮层产生神经元联系起来。潜在的更广泛的影响：我们理解皮质干细胞如何对称或不对称分裂的方法具有广泛的影响。各种干细胞中的对称和不对称决定是整个身体组织发育和再生的关键。干细胞分裂中这种平衡的破坏可能会导致一系列的病理情况，从组织发育迟缓到肿瘤发生。因此，掌握控制这一关键神经干细胞功能的基本细胞机制，不仅对于了解干细胞在正常发育过程中如何控制适当的分裂，而且对于了解它们在病理条件下的异常分裂如何导致癌症等破坏性疾病至关重要。此外，我们研究的机制可以被用来更好地定义和改进重编程策略，以生成患者特定的干细胞、神经元和神经胶质细胞，以及它们在各种脑部疾病中的潜在治疗应用。

 DESCRIPTION (provided by applicant): Neurons and glia, the operating units of the mature brain, are derived from neural stem cells (NSCs) largely during embryonic development. NSCs that give rise to neurons and glia in the cerebral cortex are particularly important to mammals as they ultimately generate the tissue that allows us to perform high-order cognitive tasks. Many neurodevelopmental disorders are caused by abnormalities in molecular and cellular machinery involved in various NSC functions. For example severe disruptions in generation and migration of new neurons can cause microcephaly and anencephaly, whereas milder developmental defects may result in imperfections in connectivity of neurons such as those becoming apparent in Autism spectrum and schizophrenia. The developmental timing of molecular and cellular signals that regulate cortical development are particularly important as temporally distinct insult may impact the cortex, activity in the brain, and behavior differentially. A number of defects associated with mechanisms that impact cytokinesis in NSCs underlie distinct diseases. Therefore understanding how stem cells divide, and what governs changes in their division during the course of brain development and NSC maturation is critical to understanding neurodevelopmental disorders. In the course of cortical development NSCs must maintain an extremely important balance in their cellular divisions. They must first expand their own pool through symmetric divisions, after which they must switch how they divide so that they can generate neurons and glia through asymmetric divisions. The current understanding of cellular and molecular mechanisms that regulate these important divisions remains fragmented and much remains to be discovered regarding master regulators of this process. We recently discovered a novel regulator of this process belongs to a family of zinc-finger specificity protein transcription factors, called Sp2. We found accumulation of stem cells at the expense of neurogenesis when we deleted the Sp2 gene only in NSCs of the developing cerebral cortex. In contrast overexpression of Sp2 rapidly pushes stem cells to delaminate from their epithelial home in the ventricular surface of the developing cortex, and precociously generate cortical neurons. We have discovered a number of intriguing cell biological themes that underlie the potent effects of Sp2 on NSCs, which we present in our preliminary data. With these findings, we propose to use a combination of state-of-the-art genetic mouse strains, cell and slice culture assays, live imaging protocols, biochemical assays, and mapping of RNA and protein landscapes that are Sp2-depenent to test the central hypothesis that Sp2-dependent transcription regulates the correct balance of proliferation and differentiation by regulating symmetric and asymmetric divisions of NSCs in the developing cerebral cortices. We provide preliminary evidence that Sp2 may carry out this critical function in NSCs through its interactions with known mechanisms and pathways of cell division. Thus, our study proposes to explore a novel mechanistic model that links molecular machineries that drive cytokinesis with asymmetric division of NSCs for production of neurons in the cerebral cortices. Potential for Broader Impact: Our approaches to understand how cortical stem cells divide symmetrically or asymmetrically have wide implications. Symmetric and asymmetric decisions in various stem cells are key to tissue development and regeneration throughout the body. Disruption of this balance in division of stem cells can lead to a range of pathological conditions from developmental retardation of tissues to oncogenesis. Therefore, undertaking the basic cellular mechanisms that control this key neural stem cell function is critical to understanding not only how appropriate divisions are controlled in stem cells during normal development, but also how their abnormal divisions in pathological conditions lead to devastating diseases such as cancer. Moreover, the mechanisms we study can be harnessed to better define and refine reprogramming strategies for generation of patient-specific stem cells, neurons, and glia and their potential therapeutic application in various brain diseases.