Musculoskeletal growth and homeostasis: does extracellular fibrillin matrix regulate Notch signaling components?

项目总结 纤维蛋白-1基因FBN1的常染色体显性突变会导致马凡综合征以及 肢端发育不良，如Weill-Marchesani综合征、关节突性发育不良和肢端发育不良 发育不良。这些遗传疾病提供了纤维蛋白-1控制肌肉骨骼生长和 动态平衡。然而，目前尚不清楚为什么FBN1的大多数突变会导致身材高大、蜘蛛指征、 关节活动过度和肌肉组织不良(马凡综合征的典型特征)，而其他基因突变 FBN1会导致相反的特征，如身材矮小、指短、关节僵硬和肌肉发达(典型 肢端发育不良)。因为纤维蛋白靶向并隔离骨等生长因子 形态发生蛋白和大潜伏的转化生长因子β复合体，阴阳的肌肉骨骼特征 在这些疾病中，纤维蛋白病变被认为反映了突变对生长因子的不同影响。在此背景下， 无论在时间上还是在空间上，仍有多种机制有待阐明。这项工作的长期目标是 了解细胞与纤维蛋白-1的相互作用如何协调出生后的生长因子信号 肌肉骨骼发育与疾病发病机制。 这项应用的短期目标是检验这样一种假设，即纤维蛋白-1之间的新相互作用 而Notch信号成分是出生后肌肉骨骼生长和内环境稳定所必需的。 生化数据表明，纤维蛋白-1与Notch信号组件结合的亲和力类似于 针对凹槽-锯齿交互作用进行测量。因为传统的Notch信令概念是基于 一个细胞上的Notch受体与一个细胞上的Notch配体(如锯齿状或Delta状)之间的细胞-细胞相互作用 相邻细胞，我们的结果显示Notch信号组件和纤维蛋白之间的相互作用，以及 细胞外基质分子，是真正具有开创性的。为了确定这些相互作用在体内的影响， 我们将使用Fbn1靶向小鼠，在这些小鼠中，Notch信号组件的结合位点已经被删除。 这个R21应用程序是“探索性/发展性的”，因为它将在体外探索/发展我们令人兴奋的 原纤维蛋白和Notch信号组件之间相互作用的发现。这些交互作用将在 活体在一种新颖的小鼠模型中可以用来在未来进一步发挥优势。我们期待这一成功 我们建议的研究的完成将为Notch的细胞外控制打开大门 发信号。此外，我们希望产生具有肌肉骨骼表型的纯合子小鼠模型 与杂合子人类中发现的那些相关(例如，长骨变短，脊柱后凸/脊柱侧弯， 不正常的肌肉结构)，但形式夸张，对开始分子研究特别有用 导致这些表型的相互作用。在未来，科学界的其他人将拥有 阐明纤维蛋白基质如何参与多种宿主中Notch信号的控制 空间和时间背景。

PROJECT SUMMARY Autosomal dominant mutations in FBN1, the gene for fibrillin-1, cause the Marfan syndrome as well as the acromelic dysplasias such as Weill-Marchesani syndrome, geleophysic dysplasia, and acromicric dysplasia. These genetic disorders provide evidence that fibrillin-1 controls musculoskeletal growth and homeostasis. However, it is unknown why most of the mutations in FBN1 cause tall stature, arachnodactyly, hypermobile joints, and poor musculature (typical features of the Marfan syndrome) while other mutations in FBN1 result in the opposite features of short stature, brachydactyly, stiff joints, and hypermusculature (typical of the acromelic dysplasias). Because fibrillins target and sequester growth factors such as Bone Morphogenetic Proteins (BMPs) and the large latent TGFβ complexes, the yin yang musculoskeletal features in the fibrillinopathies are thought to reflect different effects of mutations on growth factors. Within this context, there remain multiple mechanisms to be elucidated in both time and space. The long-term goal of this work is to learn how cellular interactions with fibrillin-1 coordinate growth factor signaling during postnatal musculoskeletal growth and pathogenesis of disease. The short-term goal of this application is to test the hypothesis that novel interactions between fibrillin-1 and Notch signaling components are required for postnatal musculoskeletal growth and homeostasis. Biochemical data indicate that fibrillin-1 binds to Notch signaling components with affinities similar to those measured for Notch-Jagged interactions. Because conventional concepts of Notch signaling are based on cell-cell interactions between Notch receptors on one cell and Notch ligands (like Jagged or Delta) on an adjacent cell, our results showing interactions between Notch signaling components and fibrillin, an extracellular matrix molecule, are truly ground-breaking. To determine the in vivo impact of these interactions, we will use Fbn1 targeted mice in which the binding site for Notch signaling components has been deleted. This R21 application is “exploratory/developmental” in that it will explore/develop our exciting in vitro findings of interactions between fibrillin and Notch signaling components. These interactions will be tested in vivo in a novel mouse model which can be used to further advantage in the future. We expect that successful completion of our proposed studies will open the door to a new paradigm for extracellular control of Notch signaling. In addition, we expect to generate homozygous mouse models with musculoskeletal phenotypes related to those found in heterozygous humans (for example, shortened long bones, kyphosis/scoliosis, abnormal musculature), but in exaggerated form, and especially useful to begin investigations of molecular interactions that cause these phenotypes. In the future, others in the scientific community will have the opportunity to elucidate how fibrillin matrix participates in the control of Notch signaling in a host of various spatial and temporal contexts.