Sensory Organ Formation in the Inner Ear

描述(申请人提供)：这项研究计划的长期目标是了解内耳感觉上皮(由毛细胞和支持细胞组成)产生的发育和分子机制。感觉上皮功能障碍是先天性耳聋、年龄相关性听力损失和前庭功能障碍的主要原因。虽然毛细胞的发育和再生受到相当大的关注，但感觉上皮中的支持细胞也是基本的细胞类型，是许多类型耳聋和平衡障碍的基础。再生毛细胞和支持细胞的一种方法是操纵产生这两种细胞类型的细胞类型，即感觉前体细胞。然而，对感觉神经前体细胞的规范和发展知之甚少。在这个提案中，我们将研究Notch信号通路在小鼠内耳感觉器官形成中的作用，重点是Notch配体之一Jagged1(JAG1)的作用。以前的工作表明，JAG1是内耳感觉前体发育所必需的，尽管其机制尚不清楚。我们推测JAG1可能在感觉前体细胞的存活、增殖或特化以及支持细胞的分化中发挥作用。为了测试这些潜在的作用，我们将在小鼠中同时使用功能丧失(目标1)和功能获得(目标2)方法。在目标1中，我们将使用条件功能丧失的Jag1小鼠等位基因和Cre/loxP技术来产生转基因小鼠品系。使用在不同发育阶段缺失JAG1的不同Cre表达小鼠品系，我们可以确定JAG1介导的Notch信号在感觉前体指定和分化中所起的作用。在目标2中，我们将利用几个可被诱导表达Notch受体(NICD)的小鼠品系，并研究在不同时间点和内耳内不同细胞类型中激活Notch的后果。这一建议将进一步确定JAG1介导的Notch信号在耳朵感觉发育和分化中的作用，并阐明Notch信号是否为操纵哺乳动物再生的合适途径。在人类中，遗传、环境和衰老因素导致内耳感觉区域的发育、功能和生存缺陷，导致耳聋和前庭功能障碍。耳朵的感觉区域由毛细胞和支持细胞组成，虽然毛细胞发育中的分子信号已被很好地研究，但对影响支持细胞发育的信号知之甚少。这一提议的结果将有助于确定导致毛细胞和支持细胞同时产生的祖细胞发育的分子级联，并阐明在耳朵中进行再生研究的适当途径。

DESCRIPTION (provided by applicant): The long-term goal of this research proposal is to understand the developmental and molecular mechanisms by which the inner ear sensory epithelium (composed of hair cells and supporting cells) is generated. Dysfunction of the sensory epithelium is a major cause of congenital deafness, age-related hearing loss, and vestibular dysfunction. While there is considerable focus on hair cell development and regeneration, the supporting cells in the sensory epithelium are also essential cell types and underlie many types of deafness and balance disorders. One approach to regenerating both hair cells and supporting cells is to manipulate the cell types that give rise to both cell types, the sensory progenitors. However, little is known about the specification and development of the sensory progenitors. In this proposal we will investigate the role of the Notch signaling pathway during sensory organ formation in the mouse inner ear, focusing on the role of one of the Notch ligands, Jagged1 (JAG1). Previous work has shown that JAG1 is required for sensory progenitor development in the inner ear, although the mechanism is not known. We hypothesize that JAG1 may play a role in the survival, proliferation, or specification of the sensory progenitors as well as in the differentiation of the supporting cells. In order to test these potential roles we will use both loss-of-function (Aim 1) and gain-of-function (Aim 2) approaches in the mouse. In Aim 1 we will use a conditional loss-of-function Jag1 mouse allele and Cre/loxP technology to generate genetically-modified mouse lines. Using different Cre-expressing mouse strains that delete JAG1 during different stages of development we can define the role that JAG1- mediated Notch signaling plays in sensory progenitor specification and differentiation. In Aim 2 we will utilize several mouse lines that can be induced to express an activated form of the Notch receptor (NICD) and investigate the consequences of activating Notch at different time points and in different cell types within the inner ear. This proposal will further define the role of JAG1-mediated Notch signaling during sensory development and differentiation within the ear as well as elucidate whether Notch signaling would be an appropriate pathway to manipulate for mammalian regeneration. In humans, genetic, environmental and aging factors contribute to defects in the development, function and survival of the sensory regions within the inner ear, leading to deafness and vestibular dysfunction. The sensory regions in the ear are composed of both hair cells and supporting cells and while the molecular signaling in hair cell development is well studied, little is known about the signals that inform supporting cell development. Results from this proposal will help to define the molecular cascade that underlies the development of the progenitor cells that give rise to both hair cells and supporting cells, and elucidate appropriate pathways to target for regenerative studies in the ear.