Function of the T-box transcription factors Tbx2 and Tbx3 in the development of the murine inner ear

内耳负责调节听觉和平衡的感觉，其特点是由许多高度专门化的机械敏感细胞(毛细胞)和非感觉细胞类型组成的异常复杂的空间排列。在位于耳蜗内的听觉感觉器官Corti的器官中，存在两种不同类型的毛细胞，它们执行完全不同的功能；内毛细胞是将声音转换为听觉信息的主要感觉细胞，而外毛细胞则充当机械放大器，增强对声音的敏感性并调节频率选择性。控制内耳从简单的上皮性小泡到其组成细胞类型的分化的细胞和分子过程尚不清楚。我们的初步工作表明，两个T-box转录因子基因Tbx2和Tbx3特异性地表达于耳上皮的不同亚区，是前庭和听觉系统的形态发生以及Corti器官内毛细胞分化所必需的。在这里，我们希望进一步定义Tbx2和Tbx3在内耳发育中的表型要求，并鉴定和表征由Tbx2和Tbx3调控的细胞和分子程序。本研究的具体目的是：1.通过对Tbx2、Tbx3和Tbx2/Tbx3在整个耳部上皮细胞条件性缺失和Tbx2的获得的小鼠的表型分析，分析Tbx2/Tbx3在小鼠内耳形态发生中的作用，并通过基因芯片和芯片序列分析鉴定Tbx2和Tbx3在这一过程中的下游效应。2.通过对小鼠Corti器官发育不同阶段前感觉、感觉和非感觉细胞中Tbx2功能丧失和获得的条件突变体的表型分析，分析Tbx2在小鼠内耳发育过程中前感觉前体细胞毛发和支持细胞分化中的作用，并通过基因芯片和芯片序列分析鉴定这一过程中的下游效应。我们期待从这些实验中对内耳形态发生和模式的细胞和分子控制以及感觉细胞在发育和动态平衡中的规范有新的见解。这一见解可能对未来有关人类患者毛细胞丢失的再生努力有用。

The inner ear, that mediates the senses of hearing and balance, is characterized by an unusually complex spatial arrangement of numerous highly specialized mechanosensitive cells (hair cells) and non-sensory cell types. In the organ of Corti, the auditory sensory organ located in the cochlea, two different subtypes of hair cells exist that fulfill entirely different functions; inner hair cells are the main sensory cells that convert sound into auditory information, whereas outer hair cells act as mechanical amplifiers that enhance sensitivity to sound and adjust frequency selectivity.The cellular and molecular processes that control the morphogenesis of the inner ear from a simple epithelial vesicle and the differentiation of its constituting cell types from common epithelial progenitors are insufficiently understood. Our preliminary work has shown that the two T-box transcription factor genes Tbx2 and Tbx3 are specifically expressed in diverse sub-regions of the otic epithelium and are crucially required therein for morphogenesis of the vestibular and the auditory system, and the differentiation of inner hair cells in the organ of Corti. Here, we wish to further define the phenotypic requirements of Tbx2 and Tbx3 in inner ear development and identify and characterize the cellular and molecular programs that are regulated by Tbx2 and Tbx3. The specific aims of this proposal are:1. Analysis of Tbx2/Tbx3 function in inner ear morphogenesis in the mouse by phenotypic characterization of mice with conditional loss of Tbx2, Tbx3 and Tbx2/Tbx3 and gain of Tbx2 in the entire otic epithelium, and the identification of downstream effectors of Tbx2 and Tbx3 in this process by microarray and ChIP-seq analysis. 2. Analysis of Tbx2 function in the differentiation of hair and supporting cells from prosensory progenitors during inner ear development in the mouse by phenotypic analysis of conditional mutants with loss and gain of Tbx2 function in prosensory, sensory and non-sensory cells at different stages of organ of Corti development, and the identification of downstream effectors in this process by microarray and ChIP-seq analysis. We expect from these experiments new insight into the cellular and molecular control of inner ear morphogenesis and patterning, and the specification of sensory cells in development and homeostasis. This insight might be useful for future regenerative efforts concerning hair cell loss in human patients.