Regulation Of Cortical Neurogenesis By Apical Complex Proteins

描述(申请人提供)：大脑皮层的正常发育依赖于成功控制皮质前体细胞的增殖和分化，这是由细胞和分子事件紧密协调的，这些事件平衡了早期出生神经元的生成和后期出生神经元的祖细胞的维持。当这一关键的发育过程没有正确发生时，大脑皮质结构就会出现异常，通常会导致智力低下、癫痫和自闭症等发育障碍。最近的研究表明，顶端复杂蛋白的功能对于维持祖细胞的命运是重要的。Pals1是一种支架蛋白，也是神经前体细胞顶端复合体蛋白的中心成分。为了阐明顶端复合蛋白控制祖细胞增殖的分子机制，建立了Pals1条件性基因敲除小鼠模型。Pals1的缺失会导致神经上皮祖细胞自我更新的缺陷，导致它们过早地退出细胞周期。Pals1基因缺陷小鼠的细胞命运变化伴随着顶端复杂蛋白和黏附连接(AJ)蛋白的异常分布，并破坏了膜结构。基于这些观察，我们假设Pals1通过与顶端复杂蛋白和AJ组分相互作用来调节膜结构和细胞极性，从而调控神经前体细胞的增殖和大脑皮层细胞的最终命运。为了验证这一假设，我们将研究Pals1在放射状胶质前体细胞(RGPS)细胞命运决定中的作用，RGPS是产生大多数神经元的细胞。Pals1在细胞命运中的直接作用将通过在RGPS中表征Pals1缺失引起的细胞命运变化以及通过分析蛋白质极化形状和分布的变化来确定。为了确定Pals1在有丝分裂中的分布和功能，我们将研究Pals1在有丝分裂过程中的分布动态，并根据Pals1遗传或Pals1亚细胞定位的变化来跟踪子细胞的命运；通过时间推移成像分析Pals1缺陷的RGP的有丝分裂缺陷，确定Pals1在祖细胞分裂中的功能。最后，为了阐明Pals1决定细胞命运的分子途径，我们将研究Pals1通过组装顶端复合体和靶向AJ和横向细胞连接来调节粘附性细胞-细胞连接的形成。我们还将探索Pals1在建立局部信号中的功能(S)，这是通过与PAR复合体的相互作用来决定细胞命运的关键。这项研究的结果将为神经前体细胞在正常发育过程中如何调控增殖提供有价值的信息，并可能对导致破坏性神经发育障碍的机制提供重要的见解。 与公共卫生相关：大脑皮层发育异常通常会导致毁灭性的神经疾病，如智力低下、自闭症和癫痫。控制神经前体细胞增殖的分子机制的研究不仅有助于更好地了解大脑皮层的正常发育，而且有助于了解其致病机制，为今后的治疗和预防提供可能。

DESCRIPTION (provided by applicant): Normal development of the cerebral cortex depends upon the successful control of proliferation and differentiation of cortical progenitor cells, which is tightly orchestrated by cellular and molecular events that balance the generation of early-born neurons with the maintenance of progenitors for later-born neurons. When this crucial developmental process does not occur properly, abnormalities in the cortical structure are a result, often leading to developmental disabilities such as mental retardation, epilepsy, and autism. Recent studies have shown that the function of apical complex proteins is important in maintaining the progenitor fate. Pals1 is a scaffolding protein and a central component of apical complex proteins in the neural progenitor cells. To delineate the molecular mechanisms that control progenitor proliferation by apical complex proteins, Pals1 conditional knockout mouse model was generated. Loss of Pals1 causes defects in self-renewal of neural epithelial progenitors, leading to their exit of the cell cycle prematurely. The cell fate changes seen in the Pals1-deficient mice are accompanied by aberrant distribution of apical complex proteins and adherens junction (AJ) proteins, and disrupted membrane structure. Based on these observations, we hypothesize that Pals1 orchestrates the control of neural progenitor proliferation and the ultimate fate of cells in the cerebral cortex by regulating membrane architecture and cell polarity through interaction with apical complex proteins and AJ components. To test this hypothesis, the function of Pals1 in cell fate decision of radial glia progenitors (RGPs), which generate the majority of neurons, will be examined. The direct function of Pals1 in the cell fate will be determined by characterizing the cell fate changes elicited by Pals1 loss in the RGPs, and by analyzing the changes in the polarized shape and distribution of proteins. To determine the Pals1 distribution and function in mitosis, we will examine the dynamics of Pals1 distribution during mitosis and follow the fate of daughter cells, depending on Pals1 inheritance or changes in subcellular localization of Pals1; and define the Pals1 function in progenitor division by analyzing the mitosis defects of Pals1-deficient RGPs through time-lapse imaging. Lastly, to delineate the molecular pathways that underlie Pals1 function of cell fate decision, we will examine the Pals1 function in regulating the formation of adhesive cell-cell junction by the assembly of the apical complex, and targeting of cadherins to AJ and the lateral cell junction. We will also explore the Pals1 function in establishment of local signaling(s) that is essential for cell fate decision by interaction with the Par complex. The results of this study will provide valuable information regarding how proliferation control of neural progenitor cells is regulated during normal development, and may lead to important insights about the mechanisms causing devastating neurodevelopmental disorders. PUBLIC HEALTH RELEVANCE: Abnormalities in the development of cerebral cortex often cause devastating neurological disorders such as mental retardation, autism and epilepsy. The studies of molecular mechanisms that control neural progenitor proliferation will provide not only the better understanding of normal development of cerebral cortex, but also knowledge about disease causing mechanism that may lead to the potential therapeutics and possible prevention in the future.