Defining the epigenetic mechanisms underlying GLI-mediated transcriptional repression

项目摘要 Sonic hedgehog（SHH）通路是颅面发育的多个步骤所必需的。突变 该途径导致毁灭性的出生缺陷，包括前脑无裂畸形和Pallister-Hall综合征。 此外，统称为颅面纤毛病的一系列疾病是由睫状体炎引起的。 影响GLI蛋白加工的突变，GLI蛋白是该途径的转录效应物。这种破坏 在加工过程中，通常导致GLI激活物（GLI-A）和GLI阻遏物（GLI-R）的减少。虽然GLI-A是 对于几个转录SHH靶点的激活是必要的，大多数基因实际上是由去- 抑制GLI-R。尽管颅面发育对GLI-R有明确的遗传要求， 它激发抑制的机制尚未确定。这一建议旨在填补我们的一个基本空白， 了解GLI-R蛋白如何在颅面发育过程中维持转录抑制。 具体来说，我试图确定GLI抑制是否通过调节表观遗传标记来调节转录， 通过在染色质可及性和GLI增强子-启动子方面物理改变染色质结构 交互.我假设GLI-R在表观遗传学上招募HDAC来维持GLI增强子。 抑制状态，限制染色质可及性，并阻止GLI增强子-启动子相互作用， 正在建立。在这个建议中的实验将提供直接的机制洞察的过程 潜在的SHH靶基因的转录调控。通过鉴定GLI结合增强子， SHH信号在颅面模式，它也将作为其他科学家研究SHH的资源 调控 !

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. !