Losa Marta, Risolino Maurizio, Li Bingsi, Hart James, Quintana Laura, Grishina Irina, Yang Hui, Choi Irene F, Lewicki Patrick, Khan Sameer, Aho Robert, Feenstra Jennifer, Vincent C Theresa, Brown Anthony M C, Ferretti Elisabetta, Williams Trevor, Selleri Licia
Program in Craniofacial Biology, Institute of Human Genetics, Eli and Edyth Broad Center of Regeneration Medicine & Stem Cell Research, Departments of Orofacial Sciences and Anatomy, University of California, San Francisco, 513 Parnassus Avenue, HSW 710, San Francisco, CA 94143, USA.
Department of Cell and Developmental Biology, Weill Cornell Medical College, 1300 York Avenue, W-512, New York, NY 10065, USA.
Development. 2018 Mar 1;145(5):dev157628. doi: 10.1242/dev.157628.
Human cleft lip with or without cleft palate (CL/P) is a common craniofacial abnormality caused by impaired fusion of the facial prominences. We have previously reported that, in the mouse embryo, epithelial apoptosis mediates fusion at the seam where the prominences coalesce. Here, we show that apoptosis alone is not sufficient to remove the epithelial layers. We observed morphological changes in the seam epithelia, intermingling of cells of epithelial descent into the mesenchyme and molecular signatures of epithelial-mesenchymal transition (EMT). Utilizing mouse lines with cephalic epithelium-specific Pbx loss exhibiting CL/P, we demonstrate that these cellular behaviors are Pbx dependent, as is the transcriptional regulation of the EMT driver Snail1. Furthermore, in the embryo, the majority of epithelial cells expressing high levels of Snail1 do not undergo apoptosis. Pbx1 loss- and gain-of-function in a tractable epithelial culture system revealed that Pbx1 is both necessary and sufficient for EMT induction. This study establishes that Pbx-dependent EMT programs mediate murine upper lip/primary palate morphogenesis and fusion via regulation of Snail1. Of note, the EMT signatures observed in the embryo are mirrored in the epithelial culture system.
人类唇裂伴或不伴腭裂（CL/P）是一种常见的颅面畸形，由面部突起融合受损引起。我们之前报道过，在小鼠胚胎中，上皮细胞凋亡介导了突起融合处的融合过程。在此，我们表明仅凋亡不足以去除上皮层。我们观察到融合处上皮细胞的形态变化、上皮来源的细胞混入间充质以及上皮-间充质转化（EMT）的分子特征。利用头部上皮特异性Pbx缺失且表现出CL/P的小鼠品系，我们证明这些细胞行为依赖于Pbx，EMT驱动因子Snail1的转录调控也是如此。此外，在胚胎中，大多数表达高水平Snail1的上皮细胞不会发生凋亡。在一个易于处理的上皮细胞培养系统中进行Pbx1功能缺失和功能获得实验表明，Pbx1对于EMT诱导既是必需的也是充分的。这项研究证实，依赖Pbx的EMT程序通过调控Snail1介导小鼠上唇/原发腭的形态发生和融合。值得注意的是，在胚胎中观察到的EMT特征在该上皮细胞培养系统中也有体现。
