Morphological and Molecular Development of Efferent Innervation of the Cochlea

项目摘要 橄榄耳蜗神经元（olivoclearneurons，OCN）位于听性脑干并投射到耳蜗，提供传出神经元的功能。 神经支配除了螺旋神经节神经元（SGN）的传入电路，容纳在 耳蜗OCN保护耳蜗免受噪音损害，并调节声音输入以及耳蜗之间的对齐 听觉回路的传入和传出成分对于适当的听觉功能是至关重要的。OCN是 由内侧橄榄耳蜗神经元（MOCs）和外侧橄榄耳蜗神经元（LOCs）组成，它们支配 外毛细胞（OHC）和SGN。MOC轴突在LOC之前到达耳蜗， 在SGN传入神经发育的重要时期短暂支配内毛细胞（IHC） 电路因此，MOC处于影响SGN发展和晚到SGN的主要位置。 OCN轴突。 到目前为止，缺乏对MOCs和LOCs的遗传访问阻碍了识别细胞间相互作用的进展 在早期耳蜗发育过程中，OCN和SGN之间存在着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 遗传工具来选择性地标记和干扰OCN，以解决早期到达OCN的假设， 轴突与SGN和IHC相互作用以形成耳蜗回路的发育。Aim 1将提前使用 在RetCreER小鼠中诱导重组，以稀疏地和选择性地标记第一个MOC轴突进入 耳蜗标记的OCN纤维和突触将被分析，以提供关键相互作用的详细说明 之间的联系。目的2将首先转录分析胚胎MOCs和LOCs 使用单细胞RNA测序来鉴定Ephs，ephrin和其他可能引导OCN的分子 发展最后，将在EphA4和ephrin-A5突变体中评估传出/传入神经连接，以阐明 关于传出寻路机制以及EphA4/ephrin-A5相互作用如何介导 耳蜗电路这些研究的结果将揭示重要的形态和分子相互作用 OCN轴突和耳蜗中其他细胞之间建立起一个功能性听觉回路。 研究培训计划将提供广泛的培训，在听觉系统，分子遗传学， 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 专业发展机会，包括指导学生和在小组中展示研究 会议、部门会谈和会议。根据该计划开发的技能将为 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 听觉回路的发展。

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.