Asymmetric Cell Division of Vertebrate Radial Glia Neural Progenitors

项目总结 不对称细胞分裂(ACD)在发育过程中对命运指定和形态发生起着至关重要的作用。 这一过程对成年后的组织动态平衡和修复也是至关重要的。DYS-对ACD的监管结果 发育/智力障碍和肿瘤发生，这使得理解潜在的细胞 和分子机制。 ACD的一个关键方面是确定细胞的极性。对无脊椎动物系统的研究 确定了重要的皮质极性调节因子，确保将命运决定因素适当地分离为两个 子代细胞。这些研究进一步阐明了不同的蛋白质复合体是如何建立和维持其 互换的大脑皮层极性。尽管有这些进展，大脑皮层定位的蛋白质如何非大脑皮层极化 分布的细胞命运决定因素还没有被很好地理解。对脊椎动物系统的研究已经开始揭示 对这些进化保守的极性调节器的功能有了新的见解。放射状胶质细胞前体细胞 脊椎动物的主要神经干细胞(RGPS)代表了一种模型细胞类型，因为它们主要是 在活跃的神经发生过程中进行ACD，以平衡自我更新和分化。我们之前的工作表明 在斑马鱼胚胎前脑RGPS中，关键的皮质极性调节因子PAR-3是建立不对称的关键 子代细胞中的缺口信号活动。目前尚不清楚PAR-3是如何建立这种不对称性的。 最近，我们首次发现，据我们所知，PAR-3存在于细胞质中，并且 与含Notch配体的内体上的动力蛋白马达复合体相关联。PAR-3和动力蛋白共同作用 在母RGP中被要求定向地将含有Notch配体的内小体运输到自身 重生女儿。此外，我们还发现，皮质PAR-3结构域从间期的顶端向 有丝分裂时向后，沿前后胚轴方向与细胞分裂方向一致。 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和Dynein一起作用于含Notch配体的内小体的极化动力学吗？ 皮质和细胞质PAR-3之间的动态关系是什么？ 间期PAR-3极轴从顶端到有丝分裂的前后部？我们的中央 假说是内在和外在机制都作用于重塑PAR-3大脑皮层的极性； 然后，极性建立了PAR-3的极化细胞质梯度，这反过来又直接促进内体 通过激活动力蛋白来实现动力学。 这项拟议的工作有望对不对称分裂和神经干细胞产生重要的新见解 脊椎动物大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，为阐明病因、激发新动力奠定基础 治疗方面的发展。

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.