Role of Ectodermal Signals in Facial Prominence Outgrowth and Development

大约75%的出生缺陷涉及头部、面部和口腔组织。虽然口面裂和其他 颅面畸形有明确的环境和遗传原因，但信息不足 关于颅面发育的机制，以使大多数这些缺陷被检测到 或在出生前预防。我们的目标是建立颅面畸形的动物模型， 对相关人类出生缺陷的诊断和治疗的机械见解。 颅面骨骼的进化和形成依赖于一个专门的细胞群， 神经嵴，在胚胎发育过程中出现在神经管的边缘。虽然这些细胞含有 除了重要的内在图案化信息之外，它们还依赖于由细胞的表面外胚层提供的信号。 以满足其生长和图案化潜力。许多研究，主要是使用 鸟类模型系统，已经证明，几个信号转导途径之间的运作， 外胚层和间充质对于面部的形态发生至关重要。事实上，操纵信号 由属于Fgf、Hedgehog（Hh）、Wnt和BMP家族的分泌因子启动的级联反应可以改变 小鸡脸的大小和形状这些研究在小鼠中更具挑战性，因为 在子宫内发育此外，小鼠基因敲除影响这些信号的关键成分， 转导途径在胚胎发生早期死亡。因此，研究这些信号事件的功能 在后来的发育过程中--如面部形态发生--必须使用 条件基因敲除技术。许多Cre重组酶转基因可以靶向基因表达 在发育中的面部外胚层中，但大多数受到其表达的程度和/或时间的限制。 最近，我们产生了一种新的Cre重组酶转基因Crect，它可以避免其中许多问题。 Crect可以在E9.5之前介导整个胚胎外胚层中的重组，并且对此具有高度特异性 组织层及其衍生物。使用Fgf 8、Ctnnb 1（β-连环蛋白）、 和Shh与Crect的研究表明，这些信号分子在外胚层表达的重要性， 面部图案这些研究还揭示了这些途径之间的广泛串扰， 塑造脸部。因此，本申请的目标是确定这些蛋白质如何单独发挥功能， 作为外胚层的网络来调节颅面的形成。在Aim I中，我们将使用Crect来调查 外胚层中Wnt/β-连环蛋白信号传导对面部发育的作用。在Aim II中，我们将执行类似的 Hh途径的分析。在目标III中，我们将测试这两种途径与Fgf 8的相互作用。结果 这些分析将揭示这些信号通路如何相互作用，以控制小鼠颅面 形态发生，并将提供有关面部生长和图案的调节的重要见解， 研究人类出生缺陷和面部重建的学科。

About 75% of birth defects involve the head, face, and oral tissues. Although orofacial clefts and other craniofacial malformations have clear environmental and genetic causes, insufficient information exists concerning the mechanisms of craniofacial development to enable the majority of these defects to be detected or prevented pre-natally. Our goal is to develop animal models of craniofacial malformations that will lead to mechanistic insight into the diagnosis and treatment of related human birth defects. The evolution and formation of the craniofacial skeleton relies on a specialized population of cells, the neural crest, arising at the margins of the neural tube during embryogenesis. While these cells contain significant intrinsic patterning information, they also rely on signals supplied by the surface ectoderm of the facial prominences to fulfill their growth and patterning potential. A number of studies, largely initiated using avian model systems, have demonstrated that several signal transduction pathways operating between the ectoderm and mesenchyme are critical for morphogenesis of the face. Indeed, manipulation of signaling cascades initiated by secreted factors belonging to the Fgf, Hedgehog (Hh), Wnt, and BMP families can alter the size and shape of the chick face. These studies have been much more challenging in the mouse due to its in utero development. Moreover, mouse gene knockouts affecting critical components of these signal transduction pathways die early in embryogenesis. Therefore, to study the function of these signaling events in later developmental processes - such as facial morphogenesis - it has been necessary to employ conditional gene knockout technology. A number of Cre recombinase transgenes can target gene expression in the developing facial ectoderm, but most are limited by the extent and/or timing of their expression. Recently, we generated a new Cre recombinase transgene, Crect, which circumvents many of these problems. Crect can mediate recombination in the entire embryonic ectoderm prior to E9.5 and is highly specific for this tissue layer and its derivatives. Preliminary data obtained using conditional alleles of Fgf8, Ctnnb1 (¿-catenin), and Shh with Crect have shown the importance of the expression of these signaling molecules in the ectoderm for facial patterning. These studies have also revealed extensive cross-talk between these pathways in shaping the face. Thus, the goal of this application is to determine how these proteins function individually and as a network in the ectoderm to regulate craniofacial formation. In Aim I we will use Crect to investigate the role of Wnt/¿-catenin signaling in the ectoderm for development of the face. In Aim II we will perform a similar analysis on the Hh pathway. In Aim III we will test the interplay of these two pathways with Fgf8. The results of these analyses will reveal how these signaling pathways interact to control mouse craniofacial morphogenesis and will provide significant insight into the regulation of facial growth and patterning pertinent to the study of human birth defects and facial reconstruction.