Morphological and Molecular Development of Efferent Innervation of the Cochlea

项目摘要 橄榄耳蜗神经元(OCNs)位于听性脑干，投射到耳蜗处，提供传出 除螺旋神经节神经元(SGN)的传入回路外，还存在于 耳蜗骨。OCNs保护耳蜗免受噪声损伤，并调制声输入，以及耳蜗管与耳蜗管之间的对准 听觉回路的传入和传出成分对正常的听觉功能至关重要。OCN是 由内侧橄榄耳蜗神经元(MOCs)和外侧橄榄耳蜗神经元(LOC)组成，支配 外毛细胞(OHCs)和SGN。MOC轴突在LOC和LOC之前到达耳蜗部 在SGN传入神经发育的重要时期内毛细胞的一过性神经支配 电路。因此，MOC处于重要地位，可以影响SGN的发展和后来到来的国家 OCN轴突。 到目前为止，缺乏获得MOC和LOC的遗传途径阻碍了在确定细胞间相互作用方面的进展 OCNs和SGN之间的关系，留下了许多悬而未决的问题 和听觉系统的外围组件对齐。本研究培训计划将使用新确定的 有选择地标记和干扰OCN的遗传工具，以解决早到OCN的假设 轴突与SGN和IHC相互作用，形成耳蜗神经回路的发育。AIM 1将提早使用 在RetCreer小鼠中诱导重组以稀疏和选择性地标记第一批进入大脑皮质的MOC轴突 耳蜗骨。将分析标记的OCN纤维和突触，以提供关键相互作用的详细描述 在MOC轴突、SGN和IHC之间。AIM 2将首先在转录水平上描述胚胎MOC和LOC 使用单细胞RNA测序来识别Ephs、Eparin和其他可能引导OCN的分子 发展。最后，将评估EphA4和ephin-A5突变体的传出/传入连接，以揭示 EphA4/ePhin-A5相互作用介导的传出通路机制 耳蜗神经回路。这些研究的结果将揭示重要的形态和分子相互作用 在OCN轴突和耳蜗内建立起作用的听觉回路的其他细胞之间。 研究培训计划将提供听觉系统、分子遗传学方面的广泛培训 方法、定量图像分析和基础生物信息学。此外，培训计划将提供 职业发展机会，包括指导学生和在小组中介绍研究 会议、部门会议和会议。根据该计划培养的技能将为 在听觉神经生物学领域的独立研究生涯，研究轴突-轴突相互作用的作用 在听觉电路的发展过程中。

Project Summary Olivocochlear neurons (OCNs) reside in the auditory brainstem and project to the cochlea, providing efferent innervation in addition to the afferent circuitry of the spiral ganglion neurons (SGNs), housed within the cochlea. OCNs protect the cochlea from noise damage and modulate acoustic input, and alignment between the afferent and efferent components of auditory circuitry is crucial for proper auditory functioning. OCNs are composed of medial olivocochlear neurons (MOCs) and lateral olivocochlear neurons (LOCs), which innervate the outer hair cells (OHCs) and SGNs, respectively. MOC axons arrive in the cochlea before LOCs and transiently innervate inner hair cells (IHCs) during an important period of development of the SGN afferent circuitry. MOCs are therefore in a prime position to influence both the development of SGNs and later-arriving OCN axons. A lack of genetic access to MOCs and LOCs has so far hindered progress in identifying the cell-cell interactions between OCNs and SGNs during early cochlear development, leaving many open questions about how central and peripheral components of the auditory system align. This research training plan will use newly identified genetic tools to selectively label and perturb OCNs in order to address the hypothesis that early arriving OCN axons interact with SGNs and IHCs to shape the development of cochlear circuitry. Aim 1 will use early induction of recombination in RetCreER mice to sparsely and selectively label the first MOC axons to enter the cochlea. Labeled OCN fibers and synapses will be analyzed to provide a detailed account of key interactions between MOC axons and SGNs and IHCs. Aim 2 will first transcriptionally profile embryonic MOCs and LOCs using single-cell RNA-sequencing to identify Ephs, ephrins, and other molecules that may guide OCN development. Finally, efferent/afferent wiring will be assessed in EphA4 and ephrin-A5 mutants to shed light on efferent pathfinding mechanisms and how EphA4/ephrin-A5 interactions mediate multiple aspects of cochlear circuitry. Results from these studies will reveal important morphological and molecular interactions between OCN axons and other cells in the cochlea that establish a functioning auditory circuit. The research training plan will provide extensive training in the auditory system, molecular genetics approaches, quantitative image analysis, and basic bioinformatics. Additionally, the training plan will offer professional development opportunities, including mentoring students and presenting research at small group meetings, departmental talks, and conferences. The skills developed under this plan will pave the way for an independent research career in the field of auditory neurobiology, studying the role of axon-axon interactions in the development of auditory circuitry.