Diversification of spiral ganglion neurons during development and in maturity

项目摘要 由内毛细胞（IHC）产生的神经信号通过一个神经元传递到更高的大脑中心。 内耳中I型螺旋神经节神经元（SGN）的功能异质群体。 虽然I型SGN已经基于基础放电分为三个生理类别， 在缺乏分子相关性的情况下，很难研究它们的发展或 他们的差异脆弱性的基础上声学过度。我们最近进行 单细胞RNA测序（scRNA-seq）发现了三种广泛的I型SGN分子 在外周解剖学和突触特征上表现出相同区别的亚型， 在生理学定义的亚组中。此外，我们还发现， 在出生后不久就明显的分离，取决于第一个阶段的自发活动。 产后一周然而，一些证据支持一种模型，即最早的分子 I型SGN的分离发生在胚胎期，可能与活性无关。这里我们 建议研究SGN身份的早期发育外观及其在 使用基于转录组的方法研究成年期。在目标1中，我们研究了 胚胎阶段的分子异质性，并测试该过程对IHC的要求。 在目标2中，我们确定了I型SGN经历变化的时间窗口， 在失去IHC驱动的激发后的分子同一性，并试图鉴定转录因子 在成熟SGN中，可以介导亚型分子身份转换的编码。一起我们 预计这些目标的完成将促进假设驱动的调查， SGN身份早期分离的潜在机制，并为 操纵成年期SGN的分子谱。我们的长期目标是获得 机制的理解如何外在效应影响细胞内在程序， 在开发过程中生成不同的SGN标识，并利用该概念框架 改变成熟神经元中的基因表达状态以实现治疗最终目标。

PROJECT ABSTRACT Neural signals generated by inner hair cells (IHCs) are transmitted to higher brain center by a functionally heterogeneous population of Type I spiral ganglion neurons (SGNs) in the inner ear. Although Type I SGNs have been grouped into three physiological classes based on basal firing rates, in the absence of molecular correlates, it has been difficult to study their development or the basis of their differential vulnerability to acoustic overexposure. We recently conducted single cell RNA-sequencing (scRNA-seq) and uncovered three broad Type I SGN molecular subtypes that exhibit the same distinctions in peripheral anatomy and synaptic features found among physiologically defined subgroups. In addition, we found that refinement of molecular segregation, which is apparent shortly after birth, depends on spontaneous activity in the first postnatal week. Some evidence, however, support a model in which the earliest molecular segregation of Type I SGNs occurs embryonically, perhaps independent of activity. Here we propose to study the early developmental appearance of SGN identities and their malleability in adulthood using a transcriptome-based approach. In Aim 1, we investigate emergence of molecular heterogeneity at embryonic stages and test the requirement of IHCs for this process. In Aim 2, we determine the temporal window over which Type I SGNs undergo changes in molecular identity upon loss of IHC-driven excitation and seek to identify a transcription factor code that can mediate switching of subtype molecular identity in mature SGNs. Together, we anticipate that completion of these aims will facilitate hypothesis-driven inquiries into the mechanisms underlying early segregation of SGN identities, and inform approaches to manipulate the molecular profiles of SGNs in adulthood. Our long-term goal is to gain a mechanistic understanding of how extrinsic effectors influence cell-intrinsic programs to generate distinct SGN identities during development and utilize that conceptual framework to alter gene expression states in mature neurons toward therapeutic end goals.