Fate acquisition and function of type I and II vestibular hair cells in mammals

项目摘要 我们的平衡感依赖于检测头部运动的前庭毛细胞。哺乳动物有 I 型和 II 型前庭毛细胞，具有不同的形态、分子和生理学特征 传入神经支配的特性和独特形式。成年哺乳动物中只有 II 型毛细胞会被替换 正常情况下和损坏后。我们不了解 I 型和 II 型毛细胞的具体功能，也不了解 它们编码并通过前庭神经发送到大脑的信息类型。此外，鲜为人知的是 关于控制每种毛细胞类型的产生和维持的机制。这些知识是 对于开发通过细胞再生恢复前庭功能的有效疗法至关重要， 移植或神经刺激（前庭植入）。 在成熟哺乳动物中，转录因子 Sox2 在 II 型毛细胞中表达，但在 I 型毛发中不表达 细胞。我们最近取得了令人兴奋的发现，即从成人 II 型毛细胞中条件性删除 Sox2 小鼠使它们获得 I 型毛细胞的形态和分子特征并建立花萼 I 型毛细胞的典型神经支配。这种转分化导致显着更高的比例 前庭上皮所有区域的 I:II 型毛细胞。 在该提案中，具有不同但高度相关专业领域的研究人员团队将利用 我们新发现的诱导成熟哺乳动物前庭毛细胞转分化的能力，以推进我们的研究 了解 I 型和 II 型毛细胞如何获得和保持其独特的特性以及每根毛发如何 细胞类型有助于前庭功能。在目标 1 中，我们将进一步测试成人 II 型中 Sox2 是否丧失功能 毛细胞导致它们转化为 I 型毛细胞，我们将确定 Sox2 是否在成人中获得功能 I 型毛细胞诱导其转分化为 II 型毛细胞。我们改变 I 型和 I 型比例的能力 成年小鼠的 II 毛细胞为解决有关功能性的长期问题提供了机会 这些细胞类型之间的差异。在目标 2 中，我们将评估每种毛细胞类型的功能贡献 通过 Sox2 条件性敲除或改变 I:II 型比例来影响传入神经活动和动物行为 异位表达。 I 型和 II 型特异性的建立依赖于基因表达的精确模式 反映在每种细胞类型的独特染色质状态中。在目标 3 中，我们将分析染色质的状态 正常 I 型毛细胞与 II 型毛细胞，并研究这些染色质状态在转分化过程中如何变化 成年后进行 Sox2 操作后。 ！

Project Abstract Our sense of balance relies on vestibular hair cells, which detect head movements. Mammals have type I and type II vestibular hair cells, which have distinct morphological, molecular, and physiological properties and unique forms of afferent innervation. Only type II hair cells are replaced in adult mammals under normal conditions and after damage. We do not understand the specific functions of type I and II hair cells nor the types of information they encode and send to the brain via the vestibular nerve. Furthermore, little is known about the mechanisms controlling the production and maintenance of each hair cell type. This knowledge is critical for developing effective therapies to restore vestibular function, through cell regeneration, transplantation, or nerve stimulation (vestibular implants). In mature mammals, the transcription factor Sox2 is expressed in type II hair cells but not in type I hair cells. We recently made the exciting discovery that conditional deletion of Sox2 from type II hair cells of adult mice causes them to acquire morphological and molecular features of type I hair cells and to establish calyx innervation typical of type I hair cells. This transdifferentiation resulted in a significantly higher proportion of type I:II hair cells in all zones of the vestibular epithelia. In this proposal, a team of investigators with distinct but highly connected areas of expertise will exploit our new-found ability to induce vestibular hair cell transdifferentiation in mature mammals to advance our understanding of how type I and II hair cells acquire and maintain their unique properties and how each hair cell type contributes to vestibular function. In Aim 1, we will further test if Sox2 loss-of-function in adult type II hair cells causes them to convert into type I hair cells, and we will determine if Sox2 gain-of-function in adult type I hair cells induces their transdifferentiation to type II hair cells. Our ability to alter proportions of type I and II hair cells in adult mice provides an opportunity to address long-standing questions regarding the functional differences between these cell types. In Aim 2, we will assess the functional contributions of each hair cell type to afferent nerve activity and to animal behavior by altering the type I:II ratio via Sox2 conditional knock-out or ectopic expression. The establishment of type I and II specificity relies on a precise pattern of gene expression reflected in the unique chromatin state of each cell type. In Aim 3, we will analyze the state of chromatin of normal type I versus type II hair cells and study how these chromatin states change during transdifferentiation after Sox2 manipulation in adulthood. !