Hair Cell Development in the Mammalian Cochlea

听觉和前庭功能依赖于功能性内耳的形成。虽然这两个系统都有多个组件，但该实验室专注于感觉上皮细胞的发育，其中包含机械感觉毛细胞和称为支持细胞的相关细胞，以及来自第八（声前庭）脑神经的神经元对这些毛细胞的神经支配。所有这三种细胞类型都来源于耳囊，耳囊是一种在发育早期邻近后脑形成的基板结构。确定指定这些细胞类型中的每一种的因素，然后指导它们组装成功能单元，是发育神经科学部分的关键目标。在过去的一年里，实验室的不同成员已经检查了这些发展过程的几个不同方面。 实验室的整体活动继续受到COVID强制减少占用率以及由于COVID相关人员短缺而对我们的动物群进行的两次强制扑杀的重大影响。 然而，我们能够发表几项合作研究和一个项目的结果，研究震荡冲击波对听觉结构和功能的影响。 作为与特拉维夫大学Karen Avrahams博士实验室合作的一部分，我们确定了人类家族中第一例由于转录因子ATOH 1突变而导致的耳聋。 Atoh1被认为是小鼠毛细胞发育所必需的已有20多年的历史，但没有人类耳聋的例子被报道，很可能是因为Atoh1的完全缺失会导致死亡。 然而，Avrahams博士的实验室能够确定一个由于ATOH 1突变而患有先天性耳聋的家庭。 我的实验室证明，ATOH 1的突变形式仍然具有功能，但突变导致蛋白质稳定性增加。 由于Atoh1在小鼠中的下调已被证明对毛细胞存活很重要，我们假设增加的稳定性实际上对毛细胞有害，导致耳聋。 作为我们合作的一部分，我们正在培育一只携带人源化Atoh1突变的小鼠，以继续这项研究。 我们还发表了一项长期项目的结果，研究震荡冲击波对听觉和前庭功能的影响。 从伊拉克或阿富汗服役归来的退伍军人通常会出现听力损失、耳鸣和眩晕。 为了确定这些投诉的生物学基础，我们与WRAIR的Joseph Long博士的实验室合作，将小鼠暴露于震荡性爆炸，然后研究听觉和前庭随时间的变化。 我们的研究结果表明，响应于冲击波的听力损失包括几种不同类型的病理，包括毛细胞损失，突触损失和鼓膜损伤。 其中一些缺陷会随着时间的推移而恢复，而另一些则似乎是永久性的。 此外，在眩晕中起关键作用的前庭系统在爆炸后似乎没有受到损害，这表明服务人员遭受的眩晕可能代表了中枢系统而不是外周系统的损害。 在其他合作中，我们确定了在小鼠耳蜗中表达的新型长非编码RNA，并继续致力于将单细胞RNA测序应用于理解感觉系统发育。

Auditory and vestibular function are dependent of the formation of a functional inner ear. While there are multiple components for both of these systems, this laboratory focuses on the development of the sensory epithelia, which contain mechanosensory hair cells and associated cells called supporting cells and on the innervation of those hair cells by neurons from the VIIIth (acousticovestibular) cranial nerve. All three of these cell types are derived from the otocyst, a placodal structure that forms adjacent to the hindbrain early in development. Identifying the factors that specify each of these cell types and then direct their assembly into functional units is a key goal of the Section on Developmental Neuroscience. During the previous year, different members of the laboratory have examined several different aspects of these developmental processes. Overall activity in the laboratory continued to be significantly affected by the COVID-mandated reduction in occupancy and two forced cullings of our animal colony because of COVID-related shortages in staffing. However, we were able to publish several collaborative studies and the results of a project examining the effects of concussive blast on auditory structure and function. As part of a collaboration with Dr. Karen Avrahams laboratory at Tel Aviv University we identified the first example of deafness in a human family as a result of mutations in the transcription factor ATOH1. Atoh1 has been known to be required for the development of hair cells in mice for over 20 years, but no examples of human deafness has been reported, most likely because complete deletion of Atoh1 leads to lethality. However, Dr. Avrahams lab was able to identify a family with congenital deafness as a result of a mutation in ATOH1. My laboratory demonstrated that the mutated form of ATOH1 is still functional but that the mutation leads to increased protein stability. Since down-regulation of Atoh1 in mice has been shown to be important for hair cell survival, we hypothesized that the increased stability is actually detrimental to hair cells, leading to deafness. As part of our collaboration, we are in the process of generating a mouse carrying the humanized Atoh1 mutation to continue this study. We also published the results of a long term project examining the effects of concussive blast on auditory and vestibular function. Loss of hearing, tinnitus and vertigo are commonly reported in veterans returning from active duty in Iraq or Afghanistan. To determine the biological basis for these complaints, we collaborated with the laboratory of Dr. Joseph Long at WRAIR to expose mice to concussive blast and then study auditory and vestibular changes over time. Our results demonstrated that hearing loss in response to concussive blast includes several different types of pathologies including loss of hair cells, loss of synapses and damage to the tympanic membrane. Some of these defects recover over time while others appear to be permanent. In addition, the vestibular system, which plays a key role in vertigo, appears to be undamaged following blast, suggesting that the vertigo suffered by service men and women may represent damage to the central, rather than peripheral, system. In other collaborations, we identified novel long non-coding RNAs that are expressed in the mouse cochlea and we continued to work on the application of single cell RNA sequencing to the understanding of sensory system development.