Mechanisms of PCP signaling in axon guidance and cochlear innervation

项目摘要 耳蜗由螺旋神经节神经元支配，螺旋神经节神经元将来自感觉毛细胞的声音信息传递到 中枢听觉目标。听觉创伤所致耳聋与两个螺旋神经节的病理改变有关 神经元和它们所支配的毛细胞，修复耳聋的一个重要方面是 诱使螺旋神经节神经元重新支配它们的毛细胞伙伴。人们普遍预计毛细胞会重新- 神经支配需要重新激活发育机制。因此，及早了解 发育事件是以再生为基础的治疗策略的重要前提。 螺旋神经节神经元的一个子集具有伤害性特征，因此具有探测声音的能力 创伤，这可能是保存功能的重要因素。这些是II型螺旋神经节神经元，它 构成少数的耳蜗神经传入，但支配所有的外毛细胞。II型神经元的发育 是独特的，有助于外毛细胞的神经支配，因为它们的外周轴突投射到内毛之外 细胞。耳蜗神经支配的一个重要组成部分是II型螺旋神经节神经元随后如何 向耳蜗基底部明显旋转90°，与多个外毛细胞突触。虽然很多方面 外毛细胞的神经支配尚不清楚，我们的实验室已经发现了两条信号通路，平面细胞 极性(PCP)信号和Eph/EPhin信号是引导外周轴突的90°转弯所必需的 朝向耳蜗基的方向。随着转录因子Prox1的丢失，也出现了类似的表型，这表明 一个监管等级控制着耳蜗神经的支配。 本研究的目的是通过研究这两个信号通路之间的关系来建立它们之间的关系 每一个细节都是相互关联的。这包括目标1中的实验，以区分可选方案 PCP蛋白在神经支配之前形成Corti器官或直接向生长发出信号的机制 圆锥体。由于轴突转动也需要EPhin受体EphA7，在目标2中，我们将确定这些 路径是线性组织的，或者如果它们是平行的和冗余的信号，则每个促进转弯。 值得注意的是，EphA7启动子包含推测的Prox1结合位点，表明这些指导 这些机制可能是转录调控的。这一假设将在目标3中得到进一步验证。 实验的重点是发育过程，我们预计这些事件必须 在毛细胞重新神经支配和修复过程中重新发生，因此拟议的研究将促进治疗 用来修复耳聋的耳蜗骨。

Project Summary The cochlea is innervated by spiral ganglion neurons, which relay sound information from sensory hair cells to central auditory targets. Deafness due to acoustic trauma is associated with pathologies in both spiral ganglion neurons and the hair cells which they innervate, and an important aspect of repairing the deafened cochlea is coaxing spiral ganglion neurons to re-innervate their hair cell partners. It is generally anticipated that hair cell re- innervation will require the reactivation of developmental mechanisms. Therefore, understanding early developmental events is an important prerequisite for regeneration-based therapeutic strategies. A subset of spiral ganglion neurons has nociceptive characteristics and are thus equipped to detect acoustic trauma, which may be important for preserving function. These are the type II spiral ganglion neurons, which constitute a minority of cochlear afferents but innervate all outer hair cells. The development of type II neurons is unique and facilitates outer hair cell innervation because their peripheral axons project beyond the inner hair cells. An important component of cochlear innervation is how the type II spiral ganglion neurons subsequently make a distinct 90° turn towards the cochlear base to synapse with multiple outer hair cells. While many aspects of outer hair cell innervation are unknown, our laboratories have found that two signaling pathways, planar cell polarity (PCP) signaling and Eph/Ephrin signaling, are required for the 90° turn that directs the peripheral axon towards the cochlear base. A similar phenotype occurs with loss of the transcription factor Prox1 suggesting that a regulatory hierarchy controls cochlear innervation. The goal of this research is to establish the relationship between these two signaling pathways by examining each in detail and relative to each other. This includes experiments in Aim 1 to distinguish between alternative mechanisms in which PCP proteins pattern the organ of Corti prior to innervation or signal directly to the growth cone. Since the Ephrin receptor EphA7 is also required for axon turning, in Aim 2 we will determine if these pathways are linearly organized or if they are parallel and redundant signals with each promoting turning. Remarkably the EphA7 promoter contains putative Prox1 binding sites suggesting that these guidance mechanisms may be transcriptionally regulated. This hypothesis will be tested further in Aim 3. While these experiments are focused on developmental processes, we anticipate that these are events which must be reenacted during hair cell re-innervation and repair, and therefore the proposed research will advance therapies for repairing the deafened cochlea.