Exploring the Role of the anterior SHF in AVSD Pathogenesis

本申请是我们现行R01-HL122906的行政补充申请，现提交于 根据NOT-OD-22-137对PA-20-272的答复(“提供行政补充 INCLUDE-对唐氏综合症患者一生中的共生状况进行调查，以了解唐氏综合症- 项目“)。 应用于唐氏综合征(DS)的意义：房室间隔缺损(AVSD) 复杂的先天性心脏缺陷，但在普通人群中相对罕见。大约0.05%的婴儿 生来就有房室间隔缺损。然而，它们在DS患者中非常常见(35-40%的DS婴儿被诊断为 一个AVSD)。在这个项目中，我们将解决国家心肺和血液的优先事项之一 研究所(NHLBI)，我们将使用动物模型，重点研究参与的形态事件 AVSD的发病机制，如果不治疗，可能会导致生命第一年的死亡。 摘要：心脏发育与先天性心脏病的关系研究一直是国际心脏学会关注的焦点。 韦瑟斯实验室工作多年。这一建议是在发现 PI引起的背侧间充质突出(DMP)。我们确定DMP是一种对 房室间充质复合体的发育及DMP的来源 来自第二心区(SHF)。我们提出的假设是，DMP可能参与了 房室间隔缺损的发病机制。事实上，在我们对16三体(TS16)小鼠的研究中，我们发现 AvsD与DMP发育不良有关。此外，我们还演示了通过实验删除 被认为对SHF的正常发育至关重要的候选基因(Alk3和Smo)导致了扰动 DMP的形成与AVSD发病机制的关系。对SHF；Smo小鼠的分析揭示了几个下调 包括Sox9在内的基因。根据我们早期的研究，我们预测Sox9将在DMP中发挥关键作用 发育和房室间隔。令人惊讶的是，尽管SHF特定的Sox9缺失会导致50%的AVSD Sox9的后代，它不是DMP发育不全的结果，而是与DMP发育失败有关 间充质帽。重要的是，几乎所有被检查的标本都发生了室间隔缺陷。 (VSD)。这一(已发表的)观察结果与我们对AVSD发病机制的研究结果相结合(参见： 研究计划)导致了关于前后部SHF(aSHF和pSHF)在 DS背景下房室缺陷的发病机制。我们建议用不同的方法进行实验 小鼠模型，包括DS的TcMAC21模型，以验证这些假设。此外，我们还将启动单人 细胞RNAseq实验以深入了解AVSD发病的分子机制， 特别关注胚胎流出道在室间隔缺损发病机制中的作用。

This application for an Administrative Supplement to our active R01-HL122906 is being submitted in response to PA-20-272 in accordance with NOT-OD-22-137 (“Availability of Administrative Supplements for the INCLUDE - INvestigation of Co-occurring conditions across the Lifespan to Understand Down syndrome - Project”). Significance of application in relation to Down syndrome (DS): Atrioventricular septal defects (AVSDs) are complex congenital heart defects but relatively rare in the general population. Approximately 0.05% of babies born have an AVSD. They are, however, very common in DS patients (35-40% of DS babies are diagnosed with an AVSD). In this project we will address one of the priorities of the National Heart, Lung, and Blood Institute (NHLBI) as we will, using animal models, focus on the morphological events involved in the pathogenesis of AVSDs which, if untreated, can be the cause of death during the first year of life. Abstract: The study of heart development as it relates to congenital heart disease has been the focus of the Wessels lab for years. This proposal is a logical extension of studies that were initiated after the discovery of the Dorsal Mesenchymal Protrusion (DMP) by the PI. We identified the DMP as a structure critically important for the development of the atrioventricular (AV) mesenchymal complex and determined that the DMP was derived from the Second Heart Field (SHF). We developed the hypothesis that the DMP could be involved in the pathogenesis of AVSDs. Indeed, in our study of the Trisomy 16 (Ts16) mouse, a model for DS, we found that AVSDs were associated with hypoplasia of the DMP. Furthermore, we demonstrated that experimentally deleting candidate genes believed to be essential for proper SHF development (Alk3 and Smo) resulted in perturbation of DMP formation and AVSD pathogenesis. Analysis of the SHF;Smo mouse revealed downregulation of several genes including Sox9. Based on our earlier studies, we predicted that Sox9 would play a critical role in DMP development and AV septation. Surprisingly, while SHF-specific Sox9 deletion resulted in AVSD in 50% of SHF;Sox9 offspring, it was not the result of DMP hypoplasia, but rather associated with failed development of the mesenchymal cap. Importantly, virtually all specimens inspected had developed a ventricular septal defect (VSD). This (published) observation in combination with results of our studies on AVSD pathogenesis (see: Research Plan) have led to new theories about the role of the anterior and posterior SHF (aSHF and pSHF) in the pathogenesis of the atrial and ventricular defects in the context of DS. We propose experiments with different mouse models, including the TcMAC21 model for DS, to test these hypotheses. In addition, we will initiate single cell RNAseq experiments to gain insight into the molecular mechanisms involved in the pathogenesis of AVSDs, specifically focusing on the role of the embryonic outflow tract in VSD pathogenesis.