Transdifferentiation in the Cochlea

项目摘要 发育中的哺乳动物耳蜗会产生两种类型的机械传感器：内毛细胞(IHCs)， 有一个突出的突触前装置，将声音信息传递给神经元和大脑；外毛细胞 被赋予电动功能的(OHC)用于声音的放大和尖锐的频率辨别。 我们发现，在IHC中表达的T-box转录因子TBX2是它们的主要调节因子 分化，阻止间质细胞向毛细胞转分化。在不同情况下消除IHC中的TBX2 胚胎和出生后阶段导致它们转化为毛细胞。我们假设TBX2不光是 诱导IHC分化，但它也在随后为它们维持自己的命运发挥作用。我们也 假设TBX2除了是必要的外，还足以引起IHC和OHC的区别 图案。我们将确定受TBX2调控并驱动IHC和OHC分化的基因，包括 从一种细胞类型到另一种细胞类型的基因表达事件链。我们还询问了TBX2是否充当了 转录激活子或抑制子，以及它是否通过修改IHC的表观基因组起作用，无论是打开 IHC分化所需的调控元件或关闭OHC分化所需的调控元件。为了测试 这些假设和替代假设，我们将对发育中和成熟的IHC、OHC和 缺乏TBX2的间质细胞(所有这些细胞都转分化为毛细胞)。最后，我们将确定中的TBX2结合位点 它调节基因的启动子和增强子，以触发和/或维持IHC的分化。 这些研究使用了由TBX2触发的IHC向HC的转分化(反之亦然) 错误调控作为阐明分子机制(转录和表观基因组学)的一种手段 其中互补的IHC和OHC是在发育中的耳蜗中产生的。

Project Summary The developing mammalian cochlea generates two types of mechanosensors: Inner hair cells (IHCs), endowed with a prominent presynaptic apparatus, transmit sound information to neurons and the brain; outer hair cells (OHCs), endowed for electromotility, are used for amplification and sharp frequency discrimination of sounds. We found that the T-box transcription factor TBX2, expressed in IHCs, is a master regulator of their differentiation, preventing IHCs from transdifferentiating into OHCs. Elimination of TBX2 from IHCs at various embryonic and postnatal stages results in their conversion into OHCs. We hypothesize that TBX2 not only induces IHC differentiation, but that it also functions subsequently for them to maintain their fate. We also hypothesize that TBX2, in addition to being necessary, is also sufficient to elicit the IHC vs OHC differentiation pattern. We will identify the genes regulated by TBX2 and driving IHC vs OHC differentiation, including the chain of gene-expression events leading from one cell type to the other. We also inquire whether TBX2 acts as a transcriptional activator or repressor, and whether it acts by modifying the epigenome of IHCs, either opening regulatory elements required for IHC differentiation or closing those required for OHC differentiation. To test these and alternative hypotheses, we will perform ATAC-seq on developing and mature IHCs, OHCs, and IHCs lacking TBX2 (all of which transdifferentiate into OHCs). Finally, we will identify the TBX2-binding sites in the promoters and enhancers of the genes it regulates in order to trigger and/or maintain IHC differentiation. These studies use the transdifferentiation of IHCs into OHCs (and vice versa) triggered by TBX2 missregulation as a means for elucidating the molecular mechanisms (transcriptomic and epigenomic) by which the complementary IHCs and OHCs are generated in the developing cochlea.