Defining the epigenetic mechanisms underlying GLI-mediated transcriptional repression

项目总结 Sonic hedgehog(SHH)通路对于颅面发育的多个步骤是必需的。基因突变 这种途径会导致毁灭性的出生缺陷，包括无前脑畸形和Pallister-Hall综合征。 此外，一系列统称为头面部纤毛病的疾病是由纤毛引起的。 影响GLI蛋白加工的突变，GLI蛋白是该途径的转录效应器。这场颠覆 在加工过程中经常导致GLI激活物(GLI-A)和GLI抑制物(GLI-R)的减少。而GLI-A是 激活几个转录的SHH靶点所必需的，实际上大多数基因都是通过去激活- 抑制GLI-R。尽管GLI-R在头面部发育过程中有明确的遗传要求，但 它引发镇压的机制尚不清楚。这项提议旨在填补我们的一个根本空白 了解GLI-R蛋白在颅面发育过程中如何维持转录抑制。 具体地说，我试图确定GLI抑制是否通过调节表观遗传标记和 通过物理改变染色质结构的染色质可及性和GLI增强子-启动子 互动。我假设GLI-R招募HDAC来维持GLI增强子在表观遗传学中 抑制状态，染色质可及性受限，阻止GLI增强子-启动子相互作用 正在建立中。该方案中的实验将提供对过程的直接机械性洞察 SHH靶基因转录调控的基础。通过识别受以下因素调控的Gli结合增强子 Shh在头面部模式中的信号，它也将为其他研究Shh的科学家提供资源 监管。 好了！

PROJECT SUMMARY The Sonic hedgehog (SHH) pathway is necessary for multiple steps of craniofacial development. Mutations in this pathway lead to devastating birth defects including holoprosencephaly and Pallister-Hall syndrome. Furthermore, a spectrum of diseases collectively referred to as craniofacial ciliopathies, are caused by ciliary mutations that affect the processing of GLI proteins, the transcriptional effectors of the pathway. This disruption in processing often leads to a reduction in both GLI activator (GLI-A) and GLI repressor (GLI-R). While GLI-A is necessary for activation of several transcriptional SHH targets, most genes are in fact activated by the de- repression of GLI-R. Despite a clear genetic requirement for GLI-R in craniofacial development, the mechanisms by which it elicits repression are undefined. This proposal aims to fill a fundamental gap in our understanding of how GLI-R proteins maintain transcriptional repression during craniofacial development. Specifically, I seek to determine if GLI repression regulates transcription by regulating epigenetic markers and by physically altering chromatin structure in terms of chromatin accessibility and GLI enhancer-promoter interactions. I hypothesize that GLI-R recruits HDACs to maintain GLI enhancers in an epigenetically repressed state with restricted chromatin accessibility and prevents GLI enhancer-promoter interactions from being established. The experiments in this proposal will provide direct mechanistic insight into the processes underlying the transcriptional regulation of SHH target genes. By identifying GLI-bound enhancers regulated by SHH signaling in craniofacial patterning, it will also serve as a resource for other scientists studying SHH regulation. !