Mechanism and Functional Significance of Polarity Reversal in Mechanosensory Organs

项目总结/摘要 前庭障碍影响多达35%的40岁以上的成年人。对前庭内耳的研究 产生了重要的见解，我们如何处理和补偿头部运动，包括存在 传入神经中的平行信息通道。例如，在黄斑器官中， 细胞采用它们的发束的相反的平面取向，因此对头部运动的反应相反。 这种高度保守的双向组织首先在侧线器官神经瘤中被描述 在鱼类中感知水的运动，但在发育过程中实现这种逆转的遗传程序是 才刚刚开始被破译因此，消融研究揭示了逆转的重要性， 前庭功能直到最近才成为可能。在此，我们建议通过以下方式解决这一问题： 研究孤儿G蛋白偶联受体（GPCRx）失活的后果， 我们在小鼠毛细胞上皮细胞方向逆转的初步数据。根据初步数据，我们 提示小鼠GPCRx在转录因子EMX 2的下游和 异源三聚体G蛋白G β i逆转由平面细胞极性蛋白建立的极性基态。 我们将测试这一假设，并使用GPCRx突变体作为动物模型，以查明极性如何 逆转形状黄斑器官反应和前庭行为的下游效应。达到这些 目标，我们将：1）使用遗传学来确定GPCRx如何在分子水平上指导逆转，解决其 在小鼠中与EMX 2、G β i和平面细胞极性蛋白的上位性关系，并使用斑马鱼测试是否 GPCRx-G β 1是一种保守的逆转效应途径。2)使用分子标记，电生理学和 钙成像以在没有极性逆转的情况下解析毛细胞成熟和功能。3)确定如何 极性逆转影响传入的组织和功能，传入记录，以及整体 前庭功能测试。我们一致的初步证据确保了 以及对该项目的高度兴趣，以及我们对几乎未研究的受体蛋白质的关注， 创新多PI团队非常适合解决小鼠和 斑马鱼侧声系统我们预计，这一合作努力将对实现 毛细胞定向逆转机制的解决、在脊椎动物中的保守性及其意义 哺乳动物的前庭生理学。对极性反转的透彻理解将有助于解释和设计 治疗前庭功能障碍。

PROJECT SUMMARY/ABSTRACT Vestibular disorders affect as many as 35% of adults past age 40. Studies of the vestibular inner ear have yielded important insights into how we process and compensate for head motion including the existence of parallel channels of information in the afferent nerve. In macular organs, for example, two populations of hair cells adopt opposite planar orientations of their hair bundles and thus opposite responses to head movements. This highly conserved bidirectional organization was first described in neuromasts, the lateral line organs sensing water movements in fish, but the genetic program implementing this reversal during development is only starting to be deciphered. Consequently, ablation studies to reveal the importance of reversal for vestibular function have not been possible until recently. Here we propose to address this question by investigating the consequences of inactivating an orphan G protein coupled receptor (GPCRx), implicated by our preliminary data in orientation reversal in mouse hair cell epithelia. Based on our preliminary data, we suggest that mouse GPCRx functions downstream of the transcription factor EMX2 and upstream of the heterotrimeric G protein Gi to reverse a ground state of polarity established by planar cell polarity proteins. We will test this hypothesis and also use the GPCRx mutant as an animal model to pinpoint how polarity reversal shapes macular organ responses and downstream effects on vestibular behaviors. To reach these goals, we will: 1) Use genetics to determine how GPCRx instructs reversal at the molecular level, solving its epistatic relationship to EMX2, Gi and planar cell polarity proteins in mice, and use zebrafish to test whether GPCRx-Gi is a conserved effector pathway for reversal. 2) Use molecular markers, electrophysiology and calcium imaging to resolve hair cell maturation and function in absence of polarity reversal. 3) Determine how polarity reversal affects afferents' organization and function, with afferent recordings, as well as overall vestibular function using behavioral tests. Our coherent body of preliminary evidence ensures the feasibility and the high interest of the project, and our focus on a virtually unstudied receptor protein guarantees innovation. The multi-PI team is ideally suited to address complementary questions in both the mouse and zebrafish acoustico-lateralis systems. We anticipate that this collaborative effort will be decisive towards solving the mechanism of hair cell orientation reversal, its conservation across vertebrates and its significance for mammalian vestibular physiology. Thorough understanding of polarity reversal will help interpret and design treatments for vestibular dysfunctions.