Multiple roles of the Notch Ligand, Jagged1, in Sensory Development of the Cochlea

摘要 听力损失是一种常见的健康问题，影响着全球数百万人。大多数听力损失是由于 科蒂氏器（Corti organ），内耳耳蜗的感觉区，受到损伤。不幸的是，一旦损坏 发生在Corti器官内的关键细胞类型，包括毛细胞（HC），支持细胞（SC）和神经元， 这些细胞无法修复或再生。了解参与的遗传和分子因素 这些关键细胞类型的开发将有助于未来的研究， 细胞因此，有必要更好地了解内耳的分子机制 发展研究表明，一些基因，如Notch配体Jag1和转录， Sox 2因子对于耳中的感觉形成至关重要。然而，目前还不清楚这些基因如何促进 感觉形成本研究的目的是研究这些基因在耳蜗发育过程中的作用。 通过两个具体目标的发展。在第一个目标中，我将调查是否有多个角色， JAG1在耳蜗发育中的作用我的初步数据表明，通过在不同时间敲除JAG 1 在发育过程中，观察到不同的表型。早期，JAG1在整个感觉神经中表达， 区域，并已牵连在感官规范。先前关于Jag1条件性基因敲除的研究显示， 感觉细胞形成的丧失，支持JAG1在感觉祖细胞发育中的作用。以前的数据也 表明Notch可能参与了后期发育的边界形成。所以，我会仔细分析。 通过在不同条件下敲除Jag 1，研究Jag 1在胚胎耳蜗发育中的功能作用 发育时间点，以确定何时以及如何需要JAG1的感觉发育。在第二 作为目标1的一部分，我将确定JAG 1是否足以扩大感觉祖细胞库。先前 研究表明，早期异位Notch激活，导致异位感觉区的形成， 这表明Notch足以驱动感觉形成。为了测试JAG1是否是介导这一过程的配体， 角色，我将在早期耳部发育过程中过度表达Jag1，并确定这是否可以创造扩大或 异位感觉区在目标2中，我将研究JAG1和SOX 2之间的关系。先前数据 显示Notch激活上调SOX 2，而敲除Jag1下调SOX 2，表明 JAG1是SOX 2的上游分子调节因子。因此，我将研究JAG1是否通过SOX 2起作用， 建立感觉祖细胞形成。为了实现这一点，我将在JAG1功能丧失中过表达Sox 2， 胚胎，以确定是否可以挽救感官信息。该提案的结果将提供一个更好的 了解耳蜗发育的分子机制，这可能是关键， 了解可能的再生能力或方法。

Abstract Hearing loss is a common health issue that affects millions of people worldwide. Most hearing loss is the result of damage to the organ of Corti, the sensory region of the cochlea in the inner ear. Unfortunately, once damage occurs to critical cell types within the organ of Corti, including hair cells (HC), supporting cells (SC), and neurons, these cells cannot be repaired or regenerated. Understanding the genetic and molecular factors involved in the development of these critical cell types will aid future studies on deriving the regeneration and repair of these cells. Thus, it is necessary to gain a better understanding of the molecular mechanisms involved in inner ear development. Studies have shown that a number of genes, such as the Notch ligand Jag1 and transcription factor Sox2, are critical for sensory formation in the ear. However, it is unclear how these genes act to promote sensory formation. The goal of this proposal is to investigate the role(s) of these genes during cochlear development through two specific aims. In the first aim, I will investigate whether there are multiple roles for JAG1 during cochlear development. My preliminary data suggest that, by knocking JAG1 out at different time points during development, different phenotypes are observed. Early, JAG1 is expressed throughout the sensory region and has been implicated in sensory specification. Previous studies of Jag1 conditional knockouts show loss of sensory cell formation, supporting JAG1 role in sensory progenitor development. Previous data also indicates that Notch may be involved in boundary formation later in development. Thus, I will dissect the functional role(s) of Jag1 during embryonic cochlear development by conditionally knocking out Jag1 at different developmental time points to determine when and how JAG1 is required for sensory development. In the second part of Aim 1, I will determine whether JAG1 is sufficient to expand the pool of sensory progenitors. Previous studies have shown that early ectopic Notch activation, leads to the formation of ectopic sensory regions, indicating Notch is sufficient to drive sensory formation. To test whether JAG1 is the ligand that mediates this role, I will overexpress Jag1 during early otic development and determine whether this can create expanded or ectopic sensory regions. In Aim 2, I will examine the relationship between JAG1 and SOX2. Previous data showed that Notch activation upregulates SOX2, whereas knocking out Jag1 downregulates SOX2, indicating that JAG1 is an upstream molecular regulator of SOX2. Thus, I will investigate whether JAG1 acts via SOX2 to establish sensory progenitor cell formation. To accomplish this, I will overexpress Sox2 in JAG1 loss-of-function embryos to determine if sensory information can be rescued. Results from this proposal will provide a better understanding of the molecular mechanisms underlying cochlear development, which may be key to understanding possible regenerative capacities or approaches.