Molecular crosstalk between apical-basal polarity and planar cell polarity in axon guidance

神经元或神经细胞有细长的突起，称为轴突，通常将电脉冲传导到远离神经元细胞体的地方。这些轴突需要找到并识别合适的伙伴，才能正确连接神经系统。为了帮助它们在发育中的胚胎中找到方向，轴突的尖端有一个高度能动和敏感的结构，称为生长锥体。虽然已经确定了一大群引导这些生长锥的分子，但介导这一过程的信号分子通路在很大程度上仍不清楚。最近的研究表明，平面细胞极性(PCP)通路在轴突引导中起着重要作用。PCP是细胞在组织平面内极化的过程，对包括神经形成在内的许多发育过程都很重要。所有的上皮细胞都表现出另一种形式的极性，称为心尖-基底(A-B)极性，这对它们的基本功能很重要。调节A-B极性的蛋白质复合体之一称为Scrib复合体，由Scribble(Scrib)、Discs Large(DLG)和致死巨型幼虫(LGL)3种蛋白质组成。最近的研究表明，PCP和A-B极性通路之间的分子相互作用表明，PCP在胚胎发育过程中具有共同的功能。我们建议研究Scrib复合体是否在发育中的脊髓和大脑的轴突引导中提供PCP途径和A-B极性之间的重要分子联系。我们将首先研究Scrib、DLG和LGL在发育中的大脑和脊髓中的表达模式，并将这些模式与名为Vangl2、Frizzled3和Celsr3的3个PCP基因的表达模式进行比较。接下来，我们将分别敲除Scrib、DLG和LGL在脊髓标本和脑培养物中的表达，包括野生型和PCP基因Vangl2突变小鼠的表达，并将使用各种标记方法来调查任何导致轴突引导的缺陷。我们的研究将为轴突引导中涉及的信号通路提供重要的见解，这些通路对于中枢神经系统的正确连接至关重要。

The neurons or nerve cells have slender projections called axons that typically conduct electrical impulses away from the neuron's cell body. These axons need to locate and recognize their appropriate partners for correct wiring of the nervous system. To help them find their way in the developing embryo, axons are tipped with a highly motile and sensitive structure called the growth cone. While a large group of molecules that guide these growth cones have been identified, the signaling molecular pathways mediating this process remain largely unknown. Recent studies have implicated an important role for a pathway called planar cell polarity (PCP) pathway in axon guidance. PCP is the process by which cells become polarized in the plane of a tissue and is important for many developmental processes including neurulation. All epithelial cells exhibit another form of polarity called apical-basal (A-B) polarity that is important for their fundamental function. One of the protein complexes that regulate A-B polarity is called the Scrib complex and is composed of 3 proteins, Scribble (Scrib), Discs Large (Dlg) and Lethal giant larvae (Lgl). Recent studies have demonstrated molecular interactions between PCP and A-B polarity pathway suggesting common functions during embryonic development. We propose to investigate if the Scrib Complex provides an essential molecular link between the PCP pathway and A-B polarity in axon guidance in the developing spinal cord and brain. We will first study the expression pattern of each of Scrib, Dlg and Lgl in the developing brain and spinal cord and compare these patterns to those of 3 PCP genes called Vangl2, Frizzled3 and Celsr3. Next, we will knockdown the expression of each of Scrib, Dlg and Lgl in spinal cord preparations and brain cultures from wild-type and from mice mutant for the PCP gene Vangl2 and we will use various labeling approaches to investigate any resulting defect in axon guidance. Our study will provide important insights into the signaling pathways involved in axon guidance that are essential for proper wiring of the central nervous system.