TRIM9 controls signaling downstream of Netrin in axon branching and guidance

描述（由申请人提供）：在神经元回路的发育过程中，轴突及其侧支在吸引和排斥信号的引导下到达突触后目标。结直肠癌（DCC）中导信号Netrin-1及其受体缺失是轴突引导和分支的重要因素。然而，Netrin-1:DCC下游控制轴突分支和引导的机制尚不清楚。我们最近发现TRIM9是一种仅在神经系统中表达的E3泛素连接酶，是网络蛋白信号传导的关键下游组分。这一提议将验证TRIM9作为网络蛋白依赖的轴突分支的主要调节剂，并通过其与网络蛋白受体DCC的直接相互作用来指导的假设。第一个目的是研究TRIM9在DCC定位中的重要性，并研究TRIM9在通过Focal Adhesion Kinase （FAK）途径调节Netrin/DCC下游信号传导中的关键作用。第二个目的是试图通过FAK的基因抑制来挽救TRIM9-/-小鼠胼胝体的异常增厚，并确定TRIM9的缺失是否会促进体内皮质轴突的错误投射。该建议结合创新的TIRF显微镜，创新的细胞生物学方法和神经解剖学研究，以阐明轴突分支和引导的关键调节因子。

DESCRIPTION (provided by applicant): During the development of neuronal circuits, axons and their collateral branches are guided by attractive and repulsive cues to postsynaptic targets. The guidance cue Netrin-1 and its receptor Deleted in Colorectal Cancer (DCC) are well-established factors in axonal guidance and branching. However, the mechanisms downstream of Netrin-1:DCC that control axon branching and guidance are not known. We recently identified TRIM9, an E3 ubiquitin ligase expressed exclusively in the nervous system, as a critical downstream component of netrin signaling. This proposal will test the hypothesis that TRIM9 acts as a master regulator of netrin dependent axon branching and guidance through its direct interaction with the netrin receptor DCC. The first aim will investigate the importance of TRIM9 in DCC localization and examine the critical role TRIM9 plays in the regulation of signaling downstream of Netrin/DCC via the Focal Adhesion Kinase (FAK) pathway. The second aim will attempt to rescue the aberrant thickening of the corpus callosum found in TRIM9-/- mice through the genetic inhibition of FAK, and determine whether loss of TRIM9 promotes the misprojection of cortical axons in vivo. This proposal combines innovative TIRF microscopy, innovative cell biological approaches, and neuroanatomical investigations in order to illuminate key regulators of proper axon branching and guidance.