TRIM9 controls signaling downstream of Netrin in axon branching and guidance

描述(申请人提供)：在神经元回路的发育过程中，轴突和它们的侧枝被吸引和排斥的线索引导到突触后目标。在结直肠癌(DCC)中缺失的导向线索Netrin-1及其受体是公认的轴突导向和分支因子。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Netrin信号的关键下游成分。这一建议将检验这样的假设，即TRIM9通过与Netrin受体DCC的直接相互作用，作为Netrin依赖的轴突分支和引导的主调节因子。这一建议结合了创新的TIRF显微镜、创新的细胞生物学方法和神经解剖学研究，以阐明适当的轴突分支和指导的关键调节因素。

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.