The Role of Cartilage Link Protein 1 (Crtl1) in Heart Development

描述(申请人提供)：透明质酸(HA)和蛋白多糖(PG)是心脏发育中的心内膜垫中的主要细胞外基质(ECM)成分。它们已被证明在心内膜向间充质转化的调节中发挥重要作用。我们最近确定软骨连接蛋白1(Crtl1)在心脏中也有表达。Crtl1介导透明质酸与前列腺素的结合，并以其稳定软骨中透明质酸/聚集素复合体的作用而闻名。在小鼠心脏中，Crtl1的表达在心内膜和心内膜衍生的房室(AV)垫中被发现，这并不令人惊讶，它主要与Verscan和HA共同定位。对Crtl1基因敲除小鼠心脏表型的彻底分析表明，在早期阶段，Crtl1-/-动物具有一系列心脏异常，包括心肌壁变薄和室间隔发育不良。晚期胎儿和新生突变小鼠表现出一系列瓣膜间隔异常，包括肌性室间隔和房室间隔缺陷。根据我们的观察，我们推测，Crtl1是发育中的心脏细胞外基质中的重要组成部分，在心肌结构和心内膜垫组织的发育中发挥着重要作用。在特定目标1中，我们计划确定心内膜表达的Crtl1在心脏发育的早期阶段中的作用。具体地说，我们将测试这一假设，即由于缺乏Crtl1，心肌细胞增殖和凋亡之间的平衡被扰乱。在目标2中，我们设计了实验，以确定Crtl1与其结合伙伴透明质酸和万西肯如何参与早期心肌发育的调节。最后，在目标3中，我们将研究Crtl1是否在EMT和/或在发育中的心脏心内膜垫内膜移植后事件的调节中发挥作用。项目相关性：每年，美国死于先天性心脏病的儿童人数几乎是所有儿童癌症死亡人数总和的两倍。几乎所有在先天性心脏病中发现的异常都与瓣膜间隔复合体有关。了解Crtl1及其相关机制在心脏发育中的作用可能会进一步加深我们对各种这些畸形的病因的了解，包括导致肌间隔缺陷的机制。

DESCRIPTION (provided by applicant): Hyaluronan (HA) and proteoglycans (PGs) are major extracellular matrix (ECM) components in the developing endocardial cushions of the heart. They have been demonstrated to play an important role in regulation of endocardial-to-mesenchymal transformation. We have recently determined that Cartilage link protein 1 (Crtl1) is expressed in the heart as well. Crtl1 mediates the binding of HA to PGs and is best known for its role in stabilizing the hyaluronan/aggrecan complex in cartilage. In the mouse heart, Crtl1 expression was found in the endocardium and in the endocardially-derived atrioventricular (AV) cushions where it is, not surprisingly, largely co-localized with versican and HA. Thorough analysis of the cardiac phenotype of the Crtl1 knock out mouse demonstrates that, at early stages, Crtl1-/- animals are characterized by a spectrum of cardiac abnormalities, including thin myocardial walls and under-developed ventricular septa. Late fetal and neonatal mutant mice display a spectrum of valvuloseptal abnormalities, including muscular ventricular and atrioventricular septal defects. From our observations, we infer that Crtl1 is an important component in the extracellular matrix of the developing heart where it plays a significant role in the development of myocardial structures and endocardial cushion tissues. In specific aim 1 we plan to determine the role of endocardially-expressed Crtl1 in early stages of cardiac development. Specifically, we will test the hypothesis that, as a result of the absence of Crtl1, the balance between myocardial proliferation and apoptosis is disturbed. In aim 2 we have designed experiments to determine how Crtl1, in combination with its binding partners hyaluronan and versican, is involved in regulation of early myocardial development. Finally, in aim 3 we will investigate whether Crtl1 plays a role in EMT and/or in the regulation of post-EMT events in the endocardial cushions of the developing heart. Relevance of project: Each year, nearly twice as many children die in the US from congenital heart disease as die from all forms of childhood cancers combined. Almost all abnormalities found in CHD involve the valvuloseptal complex. Understanding the role of Crtl1, and Crtl1-associated mechanisms, in heart development may further our knowledge of the etiology of a variety of these malformations including the mechanisms that lead to muscular septal defects.