Developmental Mechanisms of Vestibular Maculae Patterning in Mouse

描述（由申请人提供）：听觉和平衡感由内耳毛细胞介导，内耳毛细胞是具有针对运动检测优化的专门结构的感觉上皮细胞。毛细胞通过位于顶细胞表面一侧的动纤毛和静纤毛束的机械偏转来检测运动。只有束朝向动纤毛的运动才产生兴奋性反应。因此，静纤毛束的正确极化和相邻细胞之间束极性的协调是正确的前庭功能所必需的。Corti器官内的听觉毛细胞以类似的方式检测声音，相邻细胞的束极性也是协调的。这种类型的组织被称为平面细胞极性（PCP），并已在许多不同的组织和物种中描述。此外，前庭斑内的毛细胞进一步组织成两组具有相反的束极性的图案约极性反转的突变线（LPR）。这增加了可检测运动的范围和对单个方向上的运动的灵敏度。然而，尽管静纤毛束极性和毛细胞图案对前庭功能可能很重要，但尚不清楚束极化是如何在感觉上皮内启动和协调的。在这项研究计划中，指导静纤毛束极化和毛细胞定向的细胞机制将使用转基因、突变和基因敲除小鼠的组合进行评估。[The必需极性基因货车Gogh样2（vang12）的功能将通过使用新的vang12敲除小鼠（vang12TMS）分析毛细胞PCP来确定。将这些结果与vangl2突变株系环尾进行比较，尽管其具有半显性表型特征，但其已成为内耳PCP突变分析的参考。接下来，Vangl2在协调相邻细胞之间的束极性中的功能的细胞机制将通过vangl2条件性敲除系（vangl2敲除ATG）的产生和分析来测试，其中极性基因以细胞特异性方式缺失。这些实验将确定极性线索是否从细胞传播到细胞，以及vangl2是否是在内耳形态发生期间启动束极性或维持束极性所必需的。此外，其他vangl2突变导致胚胎致死性，并且这将通过产生耳特异性vangl2突变ATG条件性敲除来避免。这些小鼠将能够进行一系列行为实验，以检查毛细胞定向错误对前庭和听觉功能的影响。 公共卫生相关性：被称为毛细胞的特殊内耳感觉受体的正确形态发生和组织对于听力和平衡是必要的，这些细胞的丧失是与年龄相关的耳聋和平衡障碍的主要基础。这个项目的目的是确定毛细胞是如何定向和模式内前庭斑的椭圆囊和球囊。了解这些事件应该揭示某些形式的前庭功能障碍的基础，并将定义依赖于将替代毛细胞引入成熟内耳的治疗方法必须满足的关键参数。

DESCRIPTION (provided by applicant): The senses of hearing and balance are mediated by the hair cells of the inner ear, sensory epithelial cells with specialized architectures optimized for the detection of movement. Hair cells detect motion via the mechanical deflection of a kinocilium and stereocilia bundle located at one edge of the apical cell surface. Only movements of the bundle towards the kinocilium generate an excitatory response. Consequently the proper polarization of the stereocilia bundle and coordination of bundle polarity between adjacent cells is necessary for accurate vestibular function. Auditory hair cells within the organ of Corti detect sound in a similar fashion and the bundle polarity of adjacent cells is also coordinated. This type of organization is called planar cell polarity (PCP) and has been described in a number of different tissues and species. Moreover, hair cells within the vestibular maculae are further organized into two groups with opposite bundle polarities patterned about an abrupt line of polarity reversal (LPR). This increases the range of detectable motion and sensitivity to motion in a single direction. However, despite the likely importance of stereocilia bundle polarity and hair cell patterning for vestibular function it is not known how bundle polarization is initiated and coordinated within the sensory epithelia. Within this research proposal the cellular mechanisms guiding the polarization of the stereocilia bundle and orientation of hair cells will be evaluated using a combination of transgenic, mutant and knockout mice. [The function of the essential polarity gene van gogh-like2 (vangl2) will be determined by analyzing hair cell PCP using a novel vangl2 knockout mouse (vangl2TMS). These results will be compared to the vangl2 mutant line looptail which has become a reference for inner ear PCP mutant analysis despite having semi-dominant phenotypic characteristics.] Next the cellular mechanism of Vangl2 function in coordinating bundle polarity between adjacent cells will be tested through the production and analysis of a vangl2 conditional knockout line (vangl2floxedATG) in which the polarity gene is deleted in a cell-specific manner. These experiments will determine whether polarity cues are propagated from cell to cell and whether vangl2 is necessary for initiating bundle polarity or maintaining bundle polarity during inner ear morphogenesis. In addition, other vangl2 mutations result in embryonic lethality and this will be avoided be generating ear-specific vangl2floxedATG conditional knockouts. These mice will enable a series of behavioral experiments to examine the effects of hair cell misorientation on vestibular and auditory function. PUBLIC HEALTH RELEVANCE: Project Narrative The proper morphogenesis and organization of specialized inner ear sensory receptors called hair cells is necessary for hearing and balance, and the loss of these cells is the primary basis of age-related deafness and balance disorders. This project is designed to determine how hair cells are oriented and patterned within the within the vestibular maculae of the utricle and saccule. Understanding these events should reveal the basis of some forms of vestibular dysfunction and will define critical parameters that must be met by therapeutic approaches that rely upon introducing replacement hair cells into the mature inner ear.