Chromatin remodeling complexes in heart development

描述（由申请人提供）：先天性心脏缺陷（CHD）发生在约1%的活产婴儿中，并导致显著的死亡率和发病率。我们目前对CHD的基础知之甚少。转录因子是心脏形成的关键调节因子，心脏转录因子基因突变可导致人类CHD。这些发现强调了在发育中的心脏中需要精确剂量的转录因子蛋白。了解疾病中转录因子剂量减少的分子基础，以便能够合理设计CHD的非手术治疗是至关重要的。转录因子的功能与基因组中其靶位点的染色质结构密切相关并受其调节。染色质重塑影响转录因子的可及性和活性;这主要通过ATP依赖性染色质重塑复合物发生，其使核小体松动以允许进入转录机器。我们最近发现了哺乳动物Swi/Snf（BAF）染色质复合物的一个组成部分，称为Baf 60 c，主要在发育中的心脏中表达，在调节心脏形态发生的几个方面具有关键作用。这通过以组织特异性染色质重塑复合物的形式添加额外的调节层，建立了转录调节的新范例。我们假设Baf 60 c和BAF染色质重塑复合物在整合心脏转录因子主动调节心脏形态发生和谱系决定的关键方面中发挥关键的剂量依赖性作用。功能上确定心脏限制性BAF复合物亚基Baf 60 c和BAF复合物在心脏形态发生中所起的组织特异性和剂量敏感性作用。这将通过心脏特异性缺失Baf 60 c和Brg 1（BAF复合物ATP酶）来实现。2.揭示BAF复合体在前（次级）心脏领域谱系决定中的作用。这将通过Baf 60 c和Brg 1的前心脏区域特异性缺失，沿着遗传谱系追踪来实现。3.目的：探讨Baf 60 c与心脏转录因子相互作用的分子基础。每个目标的结果所产生的知识对于我们理解心脏模式和CHD的潜在机制至关重要。该项目所获得的结果将为冠心病的病因提供新的重要见解。我们将发现形成心脏的新的重要基因调节途径，重要的是我们将了解这些途径在人类疾病中是如何功能失调的。

DESCRIPTION (provided by applicant): Congenital heart defects (CHDs) occur in about 1% of live births, and result in significant mortality and morbidity. We currently have very little understanding of the basis of CHDs. Transcription factors are key regulators of heart formation, and mutations in cardiac transcription factor genes can cause CHDs in humans. These findings have underscored the need for precise dosage of transcription factor proteins in the developing heart. It is of paramount importance to understand the molecular basis of decreased transcription factor dosage in disease, in order to be able to rationally design non-surgical therapies for CHDs. The function of transcription factors is intimately related to and regulated by the structure of chromatin at their target sites in the genome. Chromatin remodeling affects the accessibility and activity of transcription factors; this occurs largely via ATP-dependent chromatin remodeling complexes, which loosen nucleosomes to allow access to the transcriptional machinery. We have recently identified a component of the mammalian Swi/Snf (BAF) chromatin complex, called Baf60c, which is expressed primarily in the developing heart and has key roles in regulating several aspects of cardiac morphogenesis. This has established a new paradigm in transcriptional regulation, by adding an additional layer of regulation in the form of tissue-specific chromatin remodeling complexes. We hypothesize that Baf60c and BAF chromatin remodeling complexes play critical dose-dependent roles to integrate cardiac transcription factors in active regulation of crucial aspects of cardiac morphogenesis and lineage decisions The aims of the current proposal are: 1. To functionally define the tissue-specific and dosage-sensitive roles played by the cardiac-restricted BAF complex subunit Baf60c and the BAF complex in heart morphogenesis. This will be accomplished by cardiac-specific deletion of Baf60c and Brg1, the BAF complex ATPase. 2. To uncover the role of the BAF complex in lineage decisions in the anterior (secondary) heart field. This will be accomplished by anterior heart field-specific deletion of Baf60c and Brg1, along with genetic lineage tracing. 3. To identify the molecular basis of interactions between Baf60c and cardiac transcription factors. The knowledge generated by the results of each aim will be crucial to our understanding of heart patterning and the mechanisms underlying CHDs. The results obtained in this project will provide new and important insights into the causes of CHDs. We will discover new and important gene regulation pathways that form the heart, and importantly we will understand how these pathways are dysfunctional in human disease.