Transcriptional networks establishing the precise gene expression states that define neurosensory cell identity in the inner ear

这个项目的目标是表征转录因子网络、染色质重塑因子 基因的相互作用建立并维持驱动耳部上皮细胞的精确的基因表达状态 细胞向感觉细胞或神经细胞发育，以供听力。感觉毛细胞的前体细胞 神经元在耳囊中是特定的，耳囊由耳胎板发育而来，外胚层增厚 分化形成所有的内耳结构。然而，我们对涉及的调节回路知之甚少。 前神经感觉前体细胞及其随后的神经元和感觉细胞的初始规格 因此，再生这些细胞以恢复听力损失是一个重大挑战。我们有 研究表明，Eya1与SIX1和Sox2形成关键的转录复合体，通过激活Hc来诱导HC命运 耳蜗外植体中的Atoh1。通过质谱分析，我们鉴定了SWI/SNF的成分 染色质重塑复合体作为EYA1‘S相互作用蛋白。我们证明了强迫表达 EYA1-SIX1与BRG1-BAFS在耳蜗外植体中诱导无感觉上皮细胞分化为 Neurog1+Neurod1+Tuj1+神经元。我们最近的数据揭示了Eya1-SIX1在调节 BRG1-BAFS激活Sox2启动耳廓外胚层前神经感觉命运的功能特异性 通过与多个末端3‘端Sox2增强子共结合而表达。众所周知，BRG1-BAFs在 在促进核小体耗竭以允许因子与增强剂结合方面的作用。因为染色质调节是 对于定义细胞身份至关重要，该应用程序建议系统地表征染色质 BRG1-BAF复合体的调控及其与转录因子Eya1、SIX1和Sox2的相互作用 通过检验中枢假说来定义神经感觉细胞特性的基因表达状态：1)耗尽 不同时期Eya1+One祖细胞中的BRG1降低了具有调节作用的增强子的可及性 神经感觉细胞谱系承诺和2)许多这些增强子位点由BRG1共同调节- BAFS/EYA1-SIX1或SOX2。这项研究提供了丰富的具有调控潜力的基因组位点资源和 这也是它们活动的“暂时”线索，这对建立听觉神经感觉细胞身份至关重要。

The goal of this project is to characterize how a network of transcription factors, chromatin remodeling factors and gene interactions establishes and maintains the precise gene expression states that drive otic epithelial cell development toward sensory or neuronal cells for hearing. The precursor cells for sensory hair cells (HCs) and neurons are specified in the otocyst, which develops from the otic placode, an ectoderm thickening that differentiates to form all inner ear structures. However, we know little about the regulatory circuits involved in initial specification of pro-neurosensory progenitors and their subsequent neuronal versus sensory cell commitment, thus presenting a major challenge for regenerating these cells to restore hearing loss. We have shown that the Eya1 forms a key transcriptional complex with Six1 and Sox2 to induce HC fate by activating Atoh1 in cochlear explant. Through mass spectrometry analyses, we identified components of the SWI/SNF chromatin remodeling complex as Eya1’s interacting proteins. We demonstrated that forced expression of Eya1-Six1 with Brg1-BAFs in cochlear explant induces nonsensory epithelial cells to differentiate into Neurog1+Neurod1+Tuj1+ neurons. Our recent data uncover an essential role of Eya1-Six1 in regulating the functional specificity of Brg1-BAFs to initiate pro-neurosensory fate in otic ectoderm by activating Sox2 expression through co-binding to multiple distal 3' Sox2 enhancers. The Brg1-BAFs are known to play a vital role in promoting depletion of nucleosomes to allow binding of TFs to enhancers. As chromatin regulation is critical for defining cellular identity, this application proposes to systematically characterize chromatin regulation by Brg1-BAF complex and its interaction with TFs Eya1, Six1 and Sox2 in establishing the precise gene expression states that define neurosensory cell identity by testing the central hypotheses: 1) depletion of Brg1 in Eya1+ otic progenitors at different stages reduces the accessibility of enhancers with regulatory roles in neurosensory cell lineage commitment and 2) many of these enhancer sites are co-regulated by Brg1- BAFs/Eya1-Six1 or Sox2. This study provides a rich resource of genomic sites with regulatory potential and also a ‘temporal’ clue for their activities critical to establishing neurosensory cell identity for hearing.