Antagonistic interaction of polarity complex proteins in cortical development

这项建议的总体目标是阐明导致发育缺陷的潜在机制。 通过刻画进化过程中相互作用的基本拮抗机制 保守的极性复合体蛋白。神经上皮结构的破坏导致神经元的异常 导致一系列神经发育障碍的输出和皮质畸形，包括 脑室周围异位(PH)、小头畸形和脑室增大。不对称分布的极性 蛋白质复合体对于建立和维持极化的细胞结构和 决定着不平等的细胞命运。 两个复合体(CRB/Pals1/Patj和Mupp1；Par3/Par6/aPKC)，称为心尖 极性复合体蛋白定位于顶端，一个基极性复合体(LGL/DLG/SCB)是 位于基准面。尽管它对皮质上皮结构和祖细胞分裂至关重要， 目前尚不清楚它们之间的良好平衡相互作用是否需要皮质结构和 神经发生，以及调节它们功能相互作用的细胞和分子机制也很差 明白了。为了确定它们的基本功能相互作用和潜在的分子机制，我们 产生了皮质特异的Llgl1突变体，其特征是大量的PH和皮质特异的Crb2 脑室肿大的突变体。值得注意的是，Crb1/2缺失显著减少了Llg1突变体的异位性。它 以前已经证明Llgl1与肌球蛋白结合并调节其活性，而顶极 复合蛋白aPKC和Crb2可抑制肌球蛋白活性。重要的是，因为细胞的张力和连接 缺陷与有丝分裂信号如YAP/Taz转录共激活因子的激活有关， 下游河马途径的效应者，这种拮抗也可能与异常增殖有关， 产生在Llgl1 CKO中发现的扩大的异位皮质。这些观察结果使我们假设 需要基础和顶端极性复合体之间的拮抗相互作用 在顶端建立/定位肌球蛋白，防止异常的YAP/Taz- 依赖的有丝分裂信号。为了检验这一假设，在Aim1中，我们将定义对抗关系 分析顶端和基底复合体在皮质前体细胞增殖和连接完整性中的作用 突变的小鼠。在AIM2中，我们将描述极性复杂蛋白调节连接的机制(S) 通过研究肌动球蛋白的拮抗调节来获得完整性。最后，在Aim3中，我们将确定 YAP-Taz调控极性破坏后的有丝分裂信号。我们的研究将增加对极性的理解 皮质祖细胞分裂中复杂的蛋白质相互作用，这将为我们提供新的见解 皮质畸形的发病机制，最终为新的治疗方法奠定了基础。

The overall goal of this proposal is to elucidate the mechanisms underlying the developmental defects leading to cortical malformation by characterizing the fundamental antagonistic interactions between evolutionarily conserved polarity complex proteins. Disruption of neuroepithelial structure causes abnormalities in neuronal outputs and cortical malformation that lead to a spectrum of neurodevelopmental disorders, including periventricular heterotopia (PH), microcephaly and ventriculomegaly. Asymmetrically distributed polarity protein complexes are critical for establishing and maintaining polarized cellular architecture and for determining unequal cell fate. Two complexes (Crb/Pals1/Patj and Mupp1; Par3/Par6/aPKC), termed apical polarity complex proteins, are localized at the apical side and one basal polarity complex (Lgl/DLG/Scb) is located basolaterally. Despite its critical importance for cortical epithelial structure and progenitor cell division, it is unclear whether a well-balanced interaction between them is required for cortical structure and neurogenesis, and the cellular and molecular machinery that mediates their functional interaction is also poorly understood. To identify their essential functional interactions and the underlying molecular mechanisms, we have generated a cortical-specific Llgl1 mutant characterized by massive PH and a cortical-specific Crb2 mutant with ventriculomegaly. Remarkably, Crb1/2 loss drastically reduces heterotopia in the Llg1 mutant. It has previously been shown that Llgl1 binds to myosin and regulates its activity, and that apical polarity complex proteins aPKC and Crb2 can inhibit myosin activity. Importantly, because cellular tension and junction defects are associated with the activation of mitogenic signals such as Yap/Taz transcription coactivator, downstream effectors of the Hippo pathway, this antagonism may also be linked to abnormal proliferation that produces the enlarged heterotopic cortex found in Llgl1 CKO. These observations lead us to hypothesize that the antagonistic interaction between basal and apical polarity complexes is required to establish/localize actomyosin at the apical junction and prevent activation of an abnormal Yap/Taz- dependent mitogenic signal. To test this hypothesis, in Aim1 we will define the antagonistic relationship between apical and basal complexes in cortical progenitor proliferation and junctional integrity by analyzing mutant mice. In Aim2 we will delineate the mechanism(s) by which polarity complex proteins regulate junctional integrity by investigating the antagonistic regulation of actomyosin. Lastly, in Aim3 we will determine whether Yap-Taz regulate mitogenic signaling after polarity disruption. Our study will increase understanding of polarity complex protein interactions in cortical progenitor cell division, which will provide new insights into the pathogenesis of cortical malformation and ultimately a basis for novel treatments.