Planar Polarity Mechanisms in Mammalian Inner Ear Development

描述(申请人提供)：在内耳的前庭系统中，通过位于感觉感受器毛细胞顶部的一束立体纤毛的机械偏转来检测运动。该束在形态上和生理上是极化的，因为只有束向位于顶端细胞表面一侧的一个单独的动纤毛运动才能产生兴奋反应。因此，单个毛细胞可以检测到的运动范围由立体纤毛束的极化方向决定。因此，为了对最广泛的运动做出反应，椭圆体和球囊包含数千个前庭毛细胞，它们排列成辐射阵列，跨越近360ps的立体纤毛束方向。这在一定程度上是通过将毛细胞分为两组，这两组细胞由一条极性反转线(LPR)分隔，这两组具有相反的立体纤毛束方向，并对相反方向的运动做出反应。我们的目标是确定指导平面极性发展的遗传机制。这将通过使用基因敲除和转基因小鼠模型的组合在项目过程中得到解决。具体地说，我们将测试这样的假设，即核心平面细胞极性(PCP)蛋白质建立了一个潜在的地面极性，该极性协调相邻毛细胞的方向，而不管 它们相对于LPR的位置，并且第二图案化机构定位LPR。对于这些实验，将使用阻止核心PCP信号的单基因敲除和双基因敲除小鼠品系的组合来确定基于PCP的接地极性的重要性。这将补充Wnt信号的遗传解剖及其在定位LPR中的平行作用。最后，引导LPR形成的其他因素将通过遗传标记和基于FACS的具有相反束方向的毛细胞的分离以及随后的微阵列分析来确定。尽管我们关注的是前庭平面极化的发展，但我们预计这项研究将影响我们对听觉平面极化以及其他依赖细胞极化生长或功能的器官系统的理解。

DESCRIPTION (provided by applicant): In the vestibular system of the inner ear, motion is detected via the mechanical deflection of a bundle of stereocilia located at the top of sensory receptor hair cells. The bundle is morphologically and physiologically polarized because only movements of the bundle towards a lone kinocilium positioned at one side of the apical cell surface are able to produce excitatory responses. Thus the range of motion that can be detected by an individual hair cell is determined by the polarized orientation of the stereocilia bundle. As a result, in order to respond to the broadest range of motions the utricle and saccule contain thousands of vestibular hair cells arranged in radiating arrays spanning a range of nearly 360ps of stereocilia bundle orientations. This is achieved in part by dividing the hair cell between two groups divided by a Line of Polarity Reversal (LPR) that have opposing stereocilia bundle orientations and respond to motions in opposite directions. Our goal is to identify the genetic mechanisms that direct the development of planar polarity. This will be addressed through the course of the project using combinations of knockout and transgenic mouse models. Specifically we will test the hypothesis that the core Planar Cell Polarity (PCP) proteins establis an underlying ground polarity that coordinates the orientation of adjacent hair cells regardless of their position relative to the LPR, and that a second patterning mechanism positions the LPR. For these experiments the significance of the PCP-based ground polarity will be established using a combination of single and double knockouts mouse lines that prevent core PCP signaling. This will complement a genetic dissection of Wnt-signaling and its parallel role in positioning the LPR. Finally, additional factors directing formation of the LPR will be identified through genetic labeling and FACS-based isolation of hair cells with opposite bundle orientations followed by microarray analysis. Although focused on the development of vestibular planar polarity, we anticipate that this research will impact our understanding of auditory planar polarity as well as other organ systems that rely upon cellular polarization for growth or function