Role of Supporting Cells in Cochlear Hair Cell Regeneration

描述（由申请人提供）：视网膜母细胞瘤口袋蛋白家族（pRB）是细胞周期中不可能绕过的中心淋巴结。在体内几乎所有细胞中，所有三种超磷酸化相似物比例的动态变化与细胞增殖、细胞静止和细胞凋亡直接相关。与其他组织相比，内耳pRBs的生化和分子途径相对未知。同样，对内耳感觉上皮细胞的中央淋巴结进行定量操作的效果及其促进毛细胞（HC）和支持细胞（SC）增殖的潜力仍有待确定。制定减缓听力损失进展或恢复听力损失的治疗措施是主要的临床挑战。分化的hcc特别容易受到遗传和环境致病性的损害。哺乳动物的造血干细胞在胚胎发生过程中增殖，然后退出细胞周期，分化并达到功能成熟。成年哺乳动物HC不能再生，HC死亡会导致不可逆的神经感觉性听力丧失和平衡障碍。最近的进展为两组治疗提供了原理证明：使用周期蛋白系统或口袋蛋白基因（Rb1）促进增殖，以及Atoh1诱导SC转分化（TD）为HC的有效性。结合起来，这两种方法可以模拟低等脊椎动物再生HC的能力。然而，除了原理证明之外，目前通过Rb1基因消融来调节细胞周期的尝试不太可能安全地重建丢失的HC和SC。对三种pRB成员Rb1、Rbl1 （p107）和Rbl2 （p130）的初步评估显示，它们都在内耳中表达，并且在Corti器官上和整个器官上表现出广泛的差异和相似性。任何pRB的缺失都会导致HC和SC的增加。使用各种条件和完全零突变体，我们将研究所有三种pRB在耳朵中的作用，并通过定量操纵内耳感觉上皮中pRB的固有比例来确定SCs的增殖能力（目的1）。此外，我们将分析prbs介导的先天性耳聋（dreidel）小鼠的增殖（目的2）。我们提出的研究结果将为pRB操作在SC增殖和HC再生中的治疗适用性提供见解。

DESCRIPTION (provided by applicant): The retinoblastoma family of pocket proteins (pRB) is a central node impossible to bypass during the cell cycle. Dynamic variation in the ratios of all three hyper-phosphorylated paralogs is directly correlated with cell proliferation, cellular quiescence, and apoptosis, in nearly all cells in the body. Compared to other tissues, the biochemical and molecular pathways of the pRBs in the inner ear are relatively unexplored. Likewise, the effects of quantitative manipulation of this central node in the inner ear sensory epithelia cells and its potential to promote hair cell (HC) and supporting cell (SC) proliferation is yet to be determined. Establishing therapeutic measures that slow the progression of hearing loss or restoration of lost hearing are major clinical challenges. Differentiated HCs are especially susceptible to inherited and environmental pathogenic insults. Mammalian HCs proliferate during embryogenesis, then exit the cell cycle, differentiate and become functionally mature. Adult mammalian HCs do not regenerate and HC death leads to irreversible neurosensory hearing loss and balance impairment. Recent advances have provided proof of principle for two sets of therapies: the use of the cyclin system or pocket protein gene (Rb1) to promote proliferation, and the effectiveness of Atoh1 to induce transdifferentiation (TD) SC into HC. Combined, these two approaches can mimic the ability of lower vertebrates to regenerate HC. However, beyond the proof of principle, current attempts to regulate cell cycle through genetic ablation of Rb1 are not likely to safely repopulate lost HC and SC. Preliminary assessment of the three pRB members, Rb1, Rbl1 (p107) and Rbl2 (p130) revealed that all of them are expressed in the inner ear and exhibit extensive differences and similarities with one another along and across the organ of Corti. Deletion of any pRB leads to additional rows of HC and SC. Using various conditional and complete null mutants, we will investigate the role of all three pRBs in the ear and determine the ability of SCs to proliferate as a result of quantitative manipulation of the inherent ratio of the pRBs in the inner ear sensory epithelia (aim 1). Additionally, we will analyze pRBs-mediated proliferation in congenitally deaf (dreidel) mice (aim 2). Results obtained from our proposed study will provide insights on the therapeutic applicability of pRB manipulation in SC proliferation and HC regeneration. Relevance: Adult mammalian inner ear sensory hair cells (HC) do not regenerate and their death leads to irreversible neurosensory hearing loss and balance impairment. Our research project aims to apply current approaches to quantitatively manipulate the dosage of genes involved on cell proliferation and stimulate HC regeneration.