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声音信息从感觉毛细胞传递到耳蜗。 中枢听觉目标听觉损伤引起的耳聋与两个螺旋神经节的病理有关 神经元和它们支配的毛细胞，修复受损耳蜗的一个重要方面是 诱导螺旋神经节神经元重新支配它们的毛细胞伙伴。一般认为，毛细胞再生是一种... 神经支配需要发育机制的重新激活。因此，了解早期 发育事件是基于再生的治疗策略的重要先决条件。 螺旋神经节神经元的一个子集具有伤害性特征，因此能够检测声音 创伤，这可能对保护功能很重要。这些是II型螺旋神经节神经元， 构成耳蜗传入神经的少数，但支配所有外毛细胞。II型神经元的发育 是独特的，有利于外毛细胞的神经支配，因为它们的外周轴突突出超过内毛 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如何随后 向耳蜗基底明显转向90°，与多个外毛细胞形成突触。虽然许多方面 外毛细胞神经支配的机制尚不清楚，我们的实验室已经发现两种信号通路，平面细胞 极性（PCP）信号传导和Eph/Ephrin信号传导，对于引导外周轴突的90°转向是必需的。 向耳蜗底部移动转录因子Prox 1的缺失也会出现类似的表型，这表明 调节层级控制耳蜗神经支配。 本研究的目的是通过检测这两种信号通路之间的关系， 每一个都是详细的，并且彼此相关。这包括目标1中的实验，以区分 PCP蛋白在神经支配之前对Corti器官进行模式化或直接向生长发出信号的机制 浓由于Ephrin受体EphA 7也是轴突转向所需的，在目标2中，我们将确定这些受体是否是轴突转向所必需的。 路径是线性组织的，或者如果它们是平行的和冗余的信号，则每个促进转向。 值得注意的是，EphA 7启动子含有推定的Prox 1结合位点，这表明这些指导作用 机制可能是转录调控。这一假设将在目标3中得到进一步检验。虽然这些 实验的重点是发展过程，我们预计，这些事件必须是 在毛细胞神经再生和修复过程中重新发生，因此，拟议的研究将推动治疗 修复受损的耳蜗

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.