Transdifferentiation in the Cochlea

项目摘要 发育中的哺乳动物耳蜗产生两种类型的机械传感器：内毛细胞（IHC），赋予 具有突出的突触前器官，将声音信息传递给神经元和大脑;外毛细胞 具有电活动性的外毛细胞（OHC）用于声音的放大和尖锐频率辨别。 我们发现，在IHC中表达的T-box转录因子TBX 2是其表达的主要调节因子。 分化，防止IHC转分化成OHC。在不同浓度下从IHC中消除TBX 2 胚胎和出生后阶段导致它们转化为OHC。我们假设TBX 2不仅 诱导IHC分化，但它也随后为它们发挥作用以维持它们的命运。我们也 假设TBX 2除了是必需的之外，还足以引起IHC与OHC的分化 格局我们将鉴定由TBX 2调控并驱动IHC与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TBX 2是否作为 转录激活因子或抑制因子，以及它是否通过修饰IHC的表观基因组起作用， 在一些实施方案中，免疫组化可包括IHC分化所需的调节元件或关闭OHC分化所需的那些调节元件。测试 这些假设和替代假设，我们将在发展和成熟的IHC，OHC， 缺乏TBX 2的IHC（所有这些都转分化为OHC）。最后，我们将确定TBX 2结合位点， 其调节的基因的启动子和增强子，以触发和/或维持IHC分化。 这些研究使用TBX 2触发的IHC向OHC的转分化（反之亦然 作为阐明分子机制（转录组学和表观基因组学）的手段， 在发育中的耳蜗中产生互补的IHC和OHC。

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.