Mechanisms of apical expansion in calvarial bone morphogenesis

先天性颅骨缺损如颅缝早闭和发育不良的发生率为1/2500。 对大脑和感觉器官发育有不利影响的分娩。我们缺乏基本的 了解头骨如何以及为什么向顶点生长，这影响了方向 膜内矿化和缝线融合的过程。信号传导因子与细胞 颅骨祖细胞顶端扩张的潜在机制仍不清楚。 我们最近发现小鼠颅骨骨祖细胞从眶上弓区域迁移 这种运动在条件间充质Wntless突变体中被破坏， 缺乏所有配体分泌。我们还确定了纤维连接蛋白细胞外基质的分级表达 在依赖于间充质Wnts的颅间充质中，表明细胞运动 通过其中细胞沿着纤维连接蛋白的硬度梯度迁移的硬旋转过程。这 该提案旨在体内定义颅间充质非典型Wnt的作用， 指导细胞极性和硬脊膜扩张。在这个多PI提案中，我们将利用我们的综合 在条件小鼠遗传学、活细胞成像和新兴生物物理方法方面的专业知识 在体内，以解决我们的中心假设，即间充质Wnt依赖性纤连蛋白 使颅骨骨祖细胞的集体运动朝向顶点， 硬脊膜扩张对于这一假设，在Aim 1中，我们将确定间充质Wnts的作用。 用活光片成像调节细胞运动行为的信号传导。在Aim 2中，我们将测试 如果纤连蛋白引导组织硬度梯度和SOM细胞的顶部集体运动， 硬脊膜扩张本R21提案的主要交付成果包括：1.开发一个细胞 颅骨骨形态发生过程中的行为，2. SOM-Wnt作为全局空间线索的作用， 和3.硬旋转驱动的细胞运动在颅骨骨折过程中在纤维连接蛋白基质上的作用 骨骼生长 影响：目前，我们缺乏一个概念框架来理解颅骨细胞运动。 骨扩张，尽管它在高度流行的颅缝早闭和颅骨骼 发育不良这些概念验证实验的结果将作为一个新的范例 在我们对间充质细胞的三维细胞运动的理解中， 头骨形态发生和先天性缺陷。

Congenital skull defects such as craniosynostosis and dysplasias occur in 1/2500 live births with detrimental consequences for brain and sensory organ development. We lack basic understanding of how and why the skull bones grow towards the apex, which impacts the direction of intramembranous mineralization and fusion of sutures. The signaling factors and cellular mechanisms underlying the apical expansion of skull bone progenitors remain unidentified. We recently found mouse skull bone progenitors migrate from the supraorbital arch region to the apex and this movement is disrupted in conditional mesenchyme Wntless mutants, that lack all ligand secretion. We also identified a graded expression of fibronectin extracellular matrix in the cranial mesenchyme that is dependent on mesenchyme Wnts, suggesting cell movement by a process of durotaxis in which cells migrate along a stiffness gradient of fibronectin. This proposal intends to define, in vivo, the role of the cranial mesenchyme non-canonical Wnts in directing cellular polarity and durotaxis. In this multi-PI proposal, we will leverage our integrative expertise in conditional mouse genetics, live cell imaging, and emerging biophysical approaches in vivo to address our central hypothesis that mesenchyme Wnts-dependent fibronectin orients the collective movement of calvarial bone progenitors toward the apex by durotaxis. Towards the hypothesis, in Aim1 we will identify the role of mesenchyme Wnts signaling in regulating cell movement behaviors with live light-sheet imaging. In Aim2, we will test if fibronectin directs a tissue-stiffness gradient and collective movement of SOM cells apically by durotaxis. Key deliverables of this R21 proposal include: 1. Developing a framework of cellular behaviors during calvarial bone morphogenesis, 2. the role of SOM-Wnt as a global spatial cue, and 3. the role of durotaxis driven cell movements on a graded fibronectin matrix during calvarial bone growth. Impact: Currently, we lack a conceptual framework for understanding cell movement in calvarial bone expansion, despite its role in highly prevalent craniosynostosis and cranial skeletal dysplasias. The results from these proof-of-concept experiments will serve as a new paradigm in our understanding of cell movement in 3D in mesenchymal cells and provide us fresh insights into skull bone morphogenesis and congenital defects.