Substrate-mediated collective cell migration in calvarial bone expansion and disease

总结 影响颅顶形成的先天性缺陷，如颅缝早闭或永存<$颅， 由于颅骨生长和分化异常而发生。我们对颅骨 骨骼生长，这反过来影响缝合的位置、图案和融合。哈里斯和阿蒂特实验室 最近发现了一个意想不到的和有趣的作用，细胞传感分级纤连蛋白基质， 在小鼠发育过程中优先调节颅骨祖细胞的顶端扩张。当蜂窝 板状伪足被抑制，小鼠颅骨成骨细胞不能适当地迁移，类似于当 我们有条件地删除纤连蛋白。这些发现得到了以下数据的支持： 颅缝早闭患者以及该疾病的动物模型。我们建议，分级纤维连接蛋白可能 作为颅骨成骨细胞祖细胞在颅骨顶部协调迁移的基质。我们的中央 假设颅骨生长和缝合通畅依赖于纤维连接蛋白导向的颅骨 祖细胞扩增。通过三个集中的机械和翻译目标，我们将直接测试这一点 不同数量缝合线下纤连蛋白底物介导迁移的模型和假说 病理学首先，我们将评估改变的纤维连接蛋白表达在调节颅骨生长的结果。 第二，使用新建立的小鼠和斑马鱼遗传系，我们将测试对纤连蛋白的依赖性 粘附和根尖扩张中细胞外梯度的板状伪足依赖性细胞感应的作用 颅骨第三，我们将利用颅缝早闭的患者和小鼠模型来评估共性 在临床相关畸形中纤维连接蛋白破坏以及降低纤维连接蛋白表达 在斑马鱼和小鼠体内模型中挽救颅缝早闭。我们在小鼠和 斑马鱼将使我们能够定义纤连蛋白引导的基于板状伪足的集体细胞运动的功能， 在颅骨扩张过程中的体内和纤维连接蛋白缺乏对缝线通畅性的影响。结果 这些研究将有助于详细说明成骨祖细胞基质介导的细胞迁移，并将导致新的 颅骨缺损和颅面疾病的靶向治疗策略。

Summary Congenital defects affecting the formation of the skull roof, such as craniosynostosis or persistent fontanelles, occur as a result of abnormal calvarial growth and differentiation. We lack a basic understanding of how calvarial bones grow, which in turn impacts the position, patterning, and fusion of sutures. The Harris and Atit laboratories recently uncovered an unexpected and intriguing role for cellular sensing of graded fibronectin matrix in preferentially regulating apical expansion of calvarial progenitors during mouse development. When cellular lamellipodia are inhibited, mouse calvarial osteoblasts fail to appropriately migrate resembling defects seen when we conditionally delete fibronectin. These findings are bolstered by data that fibronectin is misregulated in patients with craniosynostosis as well as animal models of this disease. We propose that graded fibronectin may act as a substrate for coordinated migration of calvarial osteoblast progenitors over the skull roof. Our central hypothesis is that calvarial growth and suture patency are dependent on fibronectin-directed calvarial progenitor cell expansion. Through three focused mechanistic and translational aims, we will directly test this model and hypothesis of fibronectin substrate-mediated migration underlying a diverse number of suture pathologies. First, we will assess outcomes of altered fibronectin expression in regulation of calvarial growth. Second, using newly established genetic lines in mouse and zebrafish, we will test the dependence on fibronectin adhesion and the role of lamellipodia-dependent cellular sensing of an extracellular gradient in apical expansion of calvaria. Third, we will capitalize on both patient and mouse models of craniosynostosis to assess commonality of fibronectin disruption in clinically relevant dysmorphologies and whether decreasing fibronectin expression rescues craniosynostosis in zebrafish and mouse models in vivo. Our unique genetic tools in both mouse and zebrafish will allow us to define the function of fibronectin guided lamellipodia-based collective cell movement in vivo during calvarial bone expansion and the impact of fibronectin deficiency on suture patency. Results from these studies will help detail the substrate-mediated cell migration of osteoblast progenitors and will lead to new strategies for targeted therapies of calvarial bone defects and craniofacial disorders.