Asymmetric Cell Division of Vertebrate Radial Glia Neural Progenitors

项目摘要 不对称细胞分裂（ACD）在发育过程中的命运特化和形态发生中起着关键作用。 这一过程对于成年期的组织稳态和修复也至关重要。ACD调节异常导致 发育/智力残疾和肿瘤发生，因此了解潜在的细胞 和分子机制。 ACD的一个关键方面是细胞极性的建立。对无脊椎动物系统的研究 确定了重要的皮质极性调节器，确保正确的分离的命运决定因素分为两个 子细胞这些研究进一步阐明了不同的蛋白质复合物是如何建立和维持其生物学特性的。 皮层极性相互作用尽管有这些进展，皮质定位的蛋白质如何在非皮质 分布的细胞命运决定因素还不清楚。对脊椎动物系统的研究已经开始揭示 这些进化保守的极性调节器的功能的新见解。放射状胶质祖细胞 神经干细胞（RGPs）是脊椎动物神经干细胞（NSC）的主要来源，由于其主要分布于神经干细胞（NSC）中，因此RGPs是一种模型细胞类型。 在活跃的神经发生期间经历ACD以平衡自我更新和分化。我们之前的工作表明， 在胚胎斑马鱼前脑RGP中，关键的皮质极性调节因子Par-3对于建立不对称性至关重要。 子细胞中的Notch信号传导活性。Par-3如何建立这种不对称性仍然是未知的。 最近，我们首次发现，据我们所知，Par-3存在于细胞质中， 与含Notch配体的内体上的动力蛋白运动复合物相关。Par-3和动力蛋白 在母体RGP中需要将含有Notch配体的内体定向转运到自体RGP中， 重生的女儿此外，我们发现皮质Par-3结构域从间期的顶端向 在有丝分裂过程中向后，与细胞分裂方向沿着前后胚胎轴对齐。 在本申请中，我们希望在这些新发现的基础上解决以下问题：1）如何 Par-3是否与动力蛋白一起指导含Notch配体的内体的极化动力学？（二） 皮质和细胞质Par-3之间的动态关系是什么？3)是什么机制重建了 Par-3极性轴从间期的顶基底部到有丝分裂的前后端？我们的中央 假设是内在和外在机制都作用于重塑Par-3皮质极性;这种皮质极性 极性然后建立Par-3的极化细胞质梯度，这反过来直接促进内体 通过激活动力蛋白实现动力学。 这项工作有望对不对称分裂和神经干产生重要的新见解 脊椎动物脑发育过程中的细胞命运调控。这些发现应该会对 揭示基本原理，为阐明疾病病因和激发新的 治疗发展

PROJECT SUMMARY Asymmetric cell division (ACD) plays a critical role in fate specification and morphogenesis during development. This process is also crucial for tissue homeostasis and repair in adulthood. Dys-regulation of ACD results in developmental/intellectual disabilities and tumorigenesis, making it critical to understand the underlying cellular and molecular mechanisms. A critical aspect of ACD is the establishment of cell polarity. Studies in invertebrate systems have identified important cortical polarity regulators, which ensure proper segregation of fate determinants into two daughter cells. These studies further shed light on how distinct protein complexes establish and maintain their reciprocal cortical polarity. Despite these advances, how cortically localized proteins polarize non-cortically distributed cell fate determinants is not well understood. Research into vertebrate systems has begun to uncover new insights into the function of these evolutionarily conserved polarity regulators. Radial glia progenitors (RGPs), the principal vertebrate neural stem cells (NSCs), represent a model cell type as they predominantly undergo ACD during active neurogenesis to balance self-renewal and differentiation. Our prior work shows that in embryonic zebrafish forebrain RGPs, the key cortical polarity regulator Par-3 is critical to establish asymmetric Notch signaling activity in daughter cells. It remains unknown how Par-3 establishes such asymmetry. Recently, we uncover, for the first time to our knowledge, that Par-3 is present in the cytosol and associates with the dynein motor complex on Notch ligand-containing endosomes. Together, Par-3 and dynein are required in the mother RGP to directionally transport Notch ligand-containing endosomes to the self- renewing daughter. Additionally, we discover that cortical Par-3 domain shifts from apical at interphase toward posterior during mitosis, to align with cell division orientation along the anteroposterior embryonic axis. In this application, we wish to build upon these new findings to address the following questions: 1) how does Par-3 work together with dynein to direct polarized dynamics of Notch ligand-containing endosomes? 2) what is the dynamic relationship between cortical and cytoplasmic Par-3? 3) What mechanisms reconstruct the axis of Par-3 polarity from apicobasal during interphase to anterior-posterior during mitosis? Our central hypothesis is that both intrinsic and extrinsic mechanisms operate to reshape Par-3 cortical polarity; this cortical polarity then sets up a polarized cytoplasmic gradient of Par-3, which in turn directly facilitates endosome dynamics by activating dynein. The proposed work is expected to yield significant new insights into asymmetric division and neural stem cell fate regulation during vertebrate brain development. These findings should have a positive impact on revealing fundamental principles and laying groundwork for elucidating disease etiology and stimulating new therapeutic development.