Regulation of auditory neuron neurite growth by activity

描述(由申请者提供)：本申请的目标是将Marlan Hansen博士培养成一名独立的医生/科学家。史蒂夫·格林博士和杰克·莉莲博士将作为导师指导他的发展。汉娜·索布科维奇博士和艾伦·瑞安博士将担任独立的外部审查员，以确保汉森博士的研究进展。在共焦显微镜技术和应用、发育神经生物学和研究生涯生存技能方面的正式课程将增加汉森博士的知识和技能，使其发展成为一名独立的研究人员。 这项建议的主要焦点是一项密集的实验室经验，旨在确定电活动对螺旋神经节神经元(SGN)神经突起生长和耳蜗神经支配的影响。这包括确定是否需要依赖于活动的信号来调节电活动的影响。大多数类型的感觉神经性听力损失是由于毛细胞受损并伴有对SGN的原发或继发性损害。人工耳蜗通过向SGN提供直接电刺激来修复最严重形式的感觉神经性听力损失。电活动调节许多神经元中的轴突生长和神经支配模式。因此，电刺激对SGN神经突起生长的影响对耳蜗体的发育、再生和植入具有重要意义。我们发现，膜去极化、钙/钙调蛋白依赖性激酶II(CaMKII)活性和蛋白激酶A(PKA)活性抑制了SGN突起的生长。我们推测电刺激通过激活CaMKII和/或PKA抑制SGN突起生长。本研究的第一个目的是通过向分离培养的SGN和耳蜗片中的SGN提供不同速率的电刺激，来确定电活动的生理模式对SGN轴突生长的影响。利用编码高度特异的CaMKII和PKA多肽抑制剂的转基因，我们将确定CaMKII和PKA活性对电活动抑制神经突起生长的需求。将具有结构性活性的CaMKII和PKA突变体引入到耳蜗片的SGN中，以测试这些分子在维持传入神经支配中的作用。这些研究的结果将提供有关电活动对SGN神经突起生长和耳蜗神经支配的影响的关键数据。

DESCRIPTION (provided by applicant): The goal of this application is to develop Dr. Marlan Hansen into an independent physician/scientist. Drs. Steve Green and Jack Lilien will serve as mentors to guide his development. Drs. Hanna Sobkowicz and Allen Ryan will serve as independent outside reviewers to ensure the progress of Dr. Hansen's development. Formal coursework in confocal microscopy techniques and application, developmental neurobiology, and research career survival skills will increase Dr. Hansen's knowledge and skills to develop into an independent investigator. The principal focus of this proposal is an intensive laboratory experience aimed at determining the effects of electrical activity on spiral ganglion neuron (SGN) neurite growth and on the innervation of the cochlea. This includes determining the necessity of activity dependent signals to mediate the effects of electrical activity. Most types of sensorineural hearing loss result from damage to the hair cells accompanied by primary or secondary damage to the SGNs. Cochlear implants rehabilitate the most severe forms of sensorineural hearing loss by providing direct electrical stimulation to the SGNs. Electrical activity regulates neurite growth and innervation patterns in many neurons. Thus, the consequences of electrical stimulation on SGN neurite growth carry important implications for cochlear development, regeneration, and implantation. We find that membrane depolarization, Ca2+/calmodulin dependent kinase II (CaMKII) activity, and protein kinase A (PKA) activity inhibit SGN neurite growth. We hypothesize that electrical stimulation inhibits SGN neurite growth by activating CaMKII and/or PKA. The first aim of this proposal is to define the effects of physiological patterns of electrical activity on SGN neurite growth by providing different rates of electrical stimulation to SGNs in dissociated cultures and in cochlear slices. Using transgenes that encode highly specific CaMKII and PKA peptide inhibitors, we will then determine the requirement of CaMKII and PKA activity for the inhibition of neurite growth by electrical activity. Constitutively active CaMKII and PKA mutants will be introduced into SGNs in cochlear slices to test the role of these molecules in the maintenance of afferent cochlear innervation. The results of these studies will provide critical data on the consequences of electrical activity on SGN neurite growth and cochlear innervation.