Mechanisms regulating cell fate decisions during Drosophila Development

正常的发育需要单个细胞致力于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命运是如何在发育过程中获得的。为此，我们一直在研究Notch信号通路的作用，该通路通过包括侧抑制和不对称细胞分裂在内的不同机制来决定几乎所有复杂动物中每种细胞类型的命运。我们研究了Notch在果蝇周围神经系统发育中的作用，Notch最初通过侧向抑制决定了一组等同细胞中的感觉器官前体细胞(SOP)的命运。随后，Notch调节SOP的不对称细胞分裂，确保命运决定因素被适当地分离到子细胞中，从而确定它们各自的命运。*Notch信号通路的一个关键成分是神经化(Neur)，它编码E3-泛素连接酶，这是侧向抑制和细胞不对称分裂所必需的。我们已经证明，Nur通过结合和泛素化Notch配体Delta和Serrate，导致它们的内吞和Notch激活，在SOP命运决定中发挥重要作用。Nur也是细胞不对称分裂所必需的，尽管它在细胞命运决定因素的分离中不起作用。有趣的是，我们最近发现Nur与蘑菇体缺陷(Mud)和Klarid结合并共定位。MUD是哺乳动物蛋白质核有丝分裂装置(NUMA)的同系物，它调节有丝分裂纺锤体的排列，对不对称细胞分裂是必不可少的。Klarid编码一个含有SUN结构域的蛋白质，与Mud/NUMA一起调节核膜的完整性和染色体的动态组织。我们推测，Nur通过调节Mud/nuA和Klarid的活性，在细胞不对称分裂中发挥重要作用。为了验证这一假设，我们将使用体外和体内方法相结合的方法来：*1.表征Nur和Mud之间的相互作用。*2.确定Nur如何影响Mud功能。*3.确定NURR和KLAR的相互作用是否存在细胞不对称分裂。总而言之，这些实验将揭示NURR在不对称细胞分裂中的新功能。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是如何协调的，以确定发育过程中细胞命运的决定。

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.*****************