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

描述（由申请方提供）：透明质酸（HA）和蛋白聚糖（PG）是发育中的心脏内膜垫中的主要细胞外基质（ECM）组分。它们已被证明在调节心内膜向间质转化中起重要作用。我们最近已经确定，心脏中也表达了Carbohydrin连接蛋白1（Crtl 1）。Crtl 1介导HA与PG的结合，并且最为人所知的是其在稳定软骨中的透明质酸/聚集蛋白聚糖复合物中的作用。在小鼠心脏中，Crtl 1表达被发现在内膜和心内膜衍生的房室（AV）垫，在那里，它是，并不奇怪，主要是共定位与多功能蛋白聚糖和HA。对Crtl 1敲除小鼠心脏表型的全面分析表明，在早期阶段，Crtl 1-/-动物的特征在于一系列心脏异常，包括心肌壁薄和心室间隔发育不全。晚期胎儿和新生儿突变小鼠显示一系列瓣膜间隔异常，包括肌性心室和房室间隔缺损。从我们的观察，我们推断，Crtl 1是一个重要的组成部分，在细胞外基质的发展心脏，它在心肌结构和内膜垫组织的发展中起着重要的作用。在具体目标1中，我们计划确定心内膜表达的Crtl 1在心脏发育早期阶段的作用。具体来说，我们将测试的假设，作为一个结果，Crtl 1的情况下，心肌细胞增殖和凋亡之间的平衡被打乱。在目标2中，我们设计了实验来确定Crtl 1如何与其结合伙伴透明质酸和多功能蛋白聚糖结合，参与早期心肌发育的调节。最后，在目标3中，我们将研究Crtl 1是否在EMT和/或在发育心脏的内膜垫中的EMT后事件的调节中起作用。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死于各种儿童癌症人数的两倍。几乎所有在CHD中发现的异常都涉及瓣膜间隔复合体。了解Crtl 1和Crtl 1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病因学的了解，包括导致肌间隔缺损的机制。

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.