Chromatin Regulation of Heart Valve Development

描述（由申请人提供）：半月瓣（SLV）疾病，包括双尖瓣主动脉瓣（BAV），非常常见，但其遗传和发育起源尚不清楚。同样，我们也不清楚被破坏的胚胎瓣膜发育是如何发展成显性瓣膜疾病的。我们的长期目标是了解基因调控如何驱动顺序发育过程，最终产生复杂的、有图案的瓣膜，以及这些过程如何在SLV疾病中出错。这些基因调控事件需要转录因子与染色质化的基因组相连接，这表明染色质调控因子是SLV发育网络的关键组成部分。一个重要的事件是发生在瓣膜发育早期的心内膜到间充质转化（EMT），以填充心内膜缓冲层（ECs），包括近端流出道（pOFT）缓冲层，为slv提供组织。我们的目标是1)了解EMT期间染色质重塑如何与细胞信号传导整合，2)确定瓣膜发育中断进展为病变slv的机制。我们的中心假设是心内膜brg1相关因子（BAF）染色质重塑复合物与Wnt信号效应物相互作用，促进pOFT EMT。因此，当心内膜Brg1被删除时，一种亚型的OFT间质被耗尽。没有这些细胞，尖端过度生长和融合导致增厚和畸形的slv，包括BAV。我们努力的基本原理是确定EMT期间染色质重塑的作用将阐明SLV疾病的起源。此外，我们的SLV疾病小鼠模型将有助于了解瓣膜疾病的细胞和分子进展。我们的具体目标是：1)确定BAF复合物与直接EMT相连接的分子网络；2)确定缺乏心内膜谱系Brg1的小鼠SLV疾病进展的机制。为了实现第一个目标，我们将比较未发表的遗传模型中发现的破坏Brg1和Wnt信号的细胞和分子pOFT缺陷。我们将应用一种变革性的新tu标记技术来定义依赖于每种途径的动态心内膜转录组。使用新的细胞培养方法，我们将测试EC细胞中BAF、Wnt效应物和染色质之间的生化相互作用。对于第二个目标，我们将使用遗传谱系追踪来确定emt衍生细胞对不同SLV区域的贡献，定义SLV间质亚群之间的相互作用，表征可能驱动SLV疾病进展的错误表达转录物，并描述一种新的成年SLV疾病小鼠模型，在临床前试验中具有潜在的用途。我们的

DESCRIPTION (provided by applicant): Semilunar valve (SLV) diseases, including bicuspid aortic valves (BAV), are remarkably common and yet their genetic and developmental origins are poorly understood. Likewise, it remains unclear how disrupted embryonic valve development progresses into overt valve disease. Our long-term goal is to understand how gene regulation drives sequential developmental processes that ultimately produce complex, patterned valves and how these processes go awry in SLV disease. These gene regulatory events require transcription factors to interface with a chromatinized genome, suggesting that chromatin regulators are key components of SLV developmental networks. One important event is an endocardial-to-mesenchymal transformation (EMT) that occurs early in valve development to populate endocardial cushions (ECs), including the proximal outflow tract (pOFT) cushions that contribute tissue to SLVs. Our objectives are to 1) understand how chromatin remodeling integrates with cell signaling during EMT, and 2) determine mechanisms by which disruptions of valve development progress into diseased SLVs. Our central hypothesis is that endocardial Brg1-associated factor (BAF) chromatin remodeling complexes interact with Wnt signaling effectors to promote pOFT EMT. As a result, when endocardial Brg1 is deleted a subtype of OFT mesenchyme is depleted. Without these cells, cusp overgrowth and fusion results in thickened and malpatterned SLVs, including BAV. The rationale for our efforts is that defining chromatin remodeling roles during EMT will shed light on how SLV disease originates. Further, our mouse models of SLV disease will enable an understanding of the cellular and molecular progression of valve disease. Our specific aims are: 1) Determine the molecular networks that the BAF complex interfaces with to direct EMT and 2) Determine mechanisms of SLV disease progression in mice lacking endocardial- lineage Brg1. In pursuit of the first Aim, we will compare cellular and molecular pOFT defects seen in unpublished genetic models disrupting Brg1 and Wnt signaling. We will apply a transformative new TU-tagging technology to define dynamic, endocardial transcriptomes dependent on each pathway. Using new cell culture approaches, we will test biochemical interactions between BAF, Wnt effectors, and chromatin in EC cells. For the second Aim, we will use genetic lineage tracing to determine contributions of EMT-derived cells to distinct SLV regions, define interactions between SLV mesenchyme sub-populations, characterize misexpressed transcripts that may drive SLV disease progression, and describe a new mouse model of adult SLV disease of potential utility in preclinical trials. Our proposed research uses novel technological and paradigmatic approaches to pursue unresolved questions of SLV development and disease. These contributions will be significant as they will shed light on the human genetics of SLV disease and inform regenerative medicine approaches. Our newly identified transcripts associated with a BAV model may represent biomarkers for disease diagnostics or therapeutic targets to prevent congenitally abnormal valves from becoming diseased.