Epithelial stratification and placode invagination are separable functions in early morphogenesis of the molar tooth.
Epithelial stratification and placode invagination are separable functions in early morphogenesis of the molar tooth.
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DOI：
10.1242/dev.130187
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发表时间：
2016-02-15
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影响因子：
--
通讯作者：
Green JB
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作者：
Li J;Chatzeli L;Panousopoulou E;Tucker AS;Green JB
外胚层器官，包括牙齿、毛囊、乳腺导管以及汗腺、粘液腺和皮脂腺等腺体，在发育过程中以安慰剂的形式开始发育，安慰剂是上皮增厚，内陷并发芽进入下层间充质。这些安慰剂分成一个基底层和几个基底层。层化和内陷的驱动机制还知之甚少。使用小鼠磨牙作为外胚层器官形态发生的模型，我们在这里表明，垂直的层状细胞分裂在形成的胎盘中丰富，层状结构依赖于细胞分裂。使用抑制剂和功能增益实验，我们证明了成纤维细胞生长因子信号对于层积是必要的和充分的，但不是内陷。我们表明，相反，Shh信号是必需的，并促进内陷，一旦基础以上的组织产生。Shh依赖的超基细胞形状暗示着会聚的迁移和嵌入，这可能是层结后胎座内陷到蕾期的原因。我们提出了一个模型，在该模型中，成纤维细胞生长因子通过不对称的细胞分裂产生超基底组织，而Shh在该组织中触发细胞重排，以驱动内陷一直到芽的形成。摘要：在小鼠的牙齿发育过程中，依赖于成纤维细胞生长因子的垂直细胞分裂使牙齿胎盘增厚，而Shh驱动细胞重排导致内陷。
Ectodermal organs, which include teeth, hair follicles, mammary ducts, and glands such as sweat, mucous and sebaceous glands, are initiated in development as placodes, which are epithelial thickenings that invaginate and bud into the underlying mesenchyme. These placodes are stratified into a basal and several suprabasal layers of cells. The mechanisms driving stratification and invagination are poorly understood. Using the mouse molar tooth as a model for ectodermal organ morphogenesis, we show here that vertical, stratifying cell divisions are enriched in the forming placode and that stratification is cell division dependent. Using inhibitor and gain-of-function experiments, we show that FGF signalling is necessary and sufficient for stratification but not invagination as such. We show that, instead, Shh signalling is necessary for, and promotes, invagination once suprabasal tissue is generated. Shh-dependent suprabasal cell shape suggests convergent migration and intercalation, potentially accounting for post-stratification placode invagination to bud stage. We present a model in which FGF generates suprabasal tissue by asymmetric cell division, while Shh triggers cell rearrangement in this tissue to drive invagination all the way to bud formation. Summary: During tooth development in mice, FGF-dependent vertical cell divisions thicken the tooth placode while Shh drives cell rearrangements that cause invagination.