头骨屋顶,或者颅骨,由互锁的骨板组成。过早缝合融合(颅骨融合,CS)或持续性fontanelles是颅骨发育中的常见缺陷。尽管这些疾病的一些遗传原因是已知的,我们对指导这些骨骼祖细胞生长和迁移的指令缺乏理解,这可能会影响缝合线的通畅性。这里,我们确定了在颅骨成骨细胞顶端扩张之前,小鼠胚胎颅间间质(CM)中纤连蛋白(FN1)的分级表达。CS的综合征形式表现出FN1表达失调,我们发现FN1在小鼠CS模型中的表达也发生了改变。CM中Fn1的条件缺失通过改变细胞极性和形状导致额骨扩张减少。为了解决骨祖细胞如何与观察到的FN1预模式相互作用,我们有条件地消融Wasl/N-Wasp以破坏迁移细胞中的F-肌动蛋白连接,影响层状足和细胞-基质相互作用。Wasl的神经c靶向缺失导致肌动蛋白网络减少和额骨原基的扩张减少,类似于条件性Fn1突变体。有趣的是,Fn1和Wasl突变体中的有缺陷的颅骨形成在增殖没有显着变化的情况下发生,生存,或成骨。最后,我们发现CM限制性Fn1缺失导致冠状缝线过早融合。这些数据支持FN1模型作为颅骨成骨细胞迁移的定向底物,这可能是许多不同遗传病因的颅骨疾病的共同机制。
The skull roof, or calvaria, is comprised of interlocking plates of bone. Premature suture fusion (craniosynostosis, CS) or persistent fontanelles are common defects in calvarial development. Although some of the genetic causes of these disorders are known, we lack an understanding of the instructions directing the growth and migration of progenitors of these bones, which may affect the suture patency. Here, we identify graded expression of Fibronectin (FN1) protein in the mouse embryonic cranial mesenchyme (CM) that precedes the apical expansion of calvarial osteoblasts. Syndromic forms of CS exhibit dysregulated FN1 expression, and we find FN1 expression is altered in a mouse CS model as well. Conditional deletion of Fn1 in CM causes diminished frontal bone expansion by altering cell polarity and shape. To address how osteoprogenitors interact with the observed FN1 prepattern, we conditionally ablate Wasl/N-Wasp to disrupt F-actin junctions in migrating cells, impacting lamellipodia and cell-matrix interaction. Neural crest-targeted deletion of Wasl results in a diminished actin network and reduced expansion of frontal bone primordia similar to conditional Fn1 mutants. Interestingly, defective calvaria formation in both the Fn1 and Wasl mutants occurs without a significant change in proliferation, survival, or osteogenesis. Finally, we find that CM-restricted Fn1 deletion leads to premature fusion of coronal sutures. These data support a model of FN1 as a directional substrate for calvarial osteoblast migration that may be a common mechanism underlying many cranial disorders of disparate genetic etiologies.