Mechanisms regulating cell fate decisions during Drosophila Development

正常的发育需要个体细胞的承诺，以适当的细胞命运和随后的分化。我的研究计划的长期目标是了解个体细胞在发育过程中的命运。为了实现这一目标，我们一直在研究Notch信号通路的作用，该信号通路通过包括侧向抑制和不对称细胞分裂在内的不同机制来决定所有复杂动物中几乎每种细胞类型的命运。我们研究了Notch在果蝇外周神经系统发育过程中的作用，其中Notch最初通过侧抑制从一组等能细胞中指定感觉器官前体细胞（SOP）的命运。随后，Notch调节SOP的不对称细胞分裂，确保命运决定簇被适当地分离到子细胞中，从而指定它们的个体命运。 侧抑制和不对称细胞分裂所需的Notch信号通路的关键组分是Neuralized（Neur），其编码E3-泛素连接酶。我们已经表明，Neur通过结合和泛素化Notch配体Delta和Serrate，导致它们的内吞作用和Notch激活，在SOP命运决定中起着至关重要的作用。Neur也是不对称细胞分裂所必需的，尽管它在细胞命运决定簇的分离中不起作用。有趣的是，我们最近发现Neur与蘑菇体缺陷（Mud）和Klaroid结合并共定位。Mud是哺乳动物蛋白质核有丝分裂器（NuMA）的同源物，其调节有丝分裂纺锤体的排列并且对于不对称细胞分裂是必需的。Klaroid编码一种含有SUN结构域的蛋白，该蛋白与Mud/NuMA一起调节核膜的完整性和染色体的动态组织。我们假设Neur通过调节Mud/NuMA和Klaroid的活性在不对称细胞分裂中起着至关重要的作用。为了验证这一假设，我们将使用体外和体内方法的组合：1。描述Neur和Mud之间的交互。2.确定Neur如何影响Mud功能。 3.确定Neur和Klar的相互作用是否导致细胞不对称分裂。 总之，这些实验将揭示Neur在不对称细胞分裂过程中的新功能。更重要的是，这些研究将深入了解侧向抑制和不对称细胞分裂如何协调，以指定发育过程中的细胞命运决定。

Normal development requires the commitment of individual cells to an appropriate cell fate and subsequent differentiation. The long-term goal of my research program is to understand how individual cell fates are acquired during development. Towards this goal, we have been studying the role of the Notch signaling pathway, which functions to determine the fate of virtually every cell type in all complex animals through distinct mechanisms that include lateral inhibition and asymmetric cell division. We have studied the role of Notch during development of the peripheral nervous system in Drosophila where Notch initially specifies the fate of sensory organ precursor cells (SOPs) from a group of equipotent cells through lateral inhibition. Subsequently, Notch regulates the asymmetric cell division of SOPs ensuring that fate determinants are appropriately segregated into daughter cells thereby specifying their individual fates. A key component of the Notch signaling pathway that is required for both lateral inhibition and asymmetric cell division is Neuralized (Neur), which encodes an E3-ubiquitin ligase. We have shown that Neur plays an essential role in SOP fate determination by binding and ubiquitinating the Notch ligands, Delta & Serrate, leading to their endocytosis and Notch activation. Neur is also required for asymmetric cell divisions although it does not play a role in the segregation of cell fate determinants. Interestingly, we have recently found that Neur binds and co-localizes with Mushroom body defect (Mud) and Klaroid. Mud is a homolog of the mammalian protein Nuclear Mitotic Apparatus (NuMA), which regulates alignment of the mitotic spindle and is essential for asymmetric cell divisions. Klaroid encodes a SUN domain containing protein, which together with Mud/NuMA, regulate the integrity of the nuclear envelope and dynamic organization of chromosomes. We hypothesize that Neur plays an essential role in asymmetric cell division by regulating the activity of Mud/NuMA and Klaroid. To test this hypothesis, we will use a combination of in vitro and in vivo approaches to: 1. Characterize the interaction between Neur and Mud. 2. Determine how Neur affects Mud function. 3. Determine whether the interaction of Neur and Klar asymmetric cell division. Altogether, these experiments will reveal novel functions for Neur during asymmetric cell division. More importantly, these studies will provide insight into how lateral inhibition and asymmetric cell divisions are coordinated to specify cell fate decisions during development.