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。尽管口面部裂隙和其他 颅面畸形有明确的环境和遗传原因，信息不足 关于颅面发育的机制，以使大多数这些缺陷能够被检测到 或先天预防。我们的目标是开发颅面畸形的动物模型，这将导致 对相关人类出生缺陷的诊断和治疗的机械洞察力。 颅面部骨骼的进化和形成依赖于一种特殊的细胞群体，即 在胚胎发育过程中，神经管边缘长出的神经脊。虽然这些单元格包含 重要的内在图案信息，它们也依赖于由表面外胚层提供的信号 面部突起，以实现其生长和图案的潜力。许多研究，主要是使用 禽类模型系统，已经证明了几条信号转导通路在 外胚层和间充质是面部形态发生的关键。事实上，对信号的操纵 由属于成纤维细胞生长因子、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。这些研究在小鼠身上更具挑战性，因为它 在子宫内发育。此外，小鼠基因敲除会影响这些信号的关键成分 转导通路在胚胎发育中很早就死亡了。因此，要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--有必要使用 条件性基因敲除技术。许多Cre重组酶转基因基因可以靶向基因表达 在发育中的面部外胚层，但大多数都受到其表达的范围和/或时机的限制。 最近，我们创造了一种新的Cre重组酶转基因基因Crect，它绕过了许多这样的问题。 在E9.5之前，CRECT可以介导整个胚胎外胚层中的重组，并且对此具有高度的特异性 组织层及其衍生物。利用条件等位基因Fgf8，CTNNB1(连环蛋白)， Shh和Crect已经证明了这些信号分子在外胚层中表达的重要性 用来做脸部图案。这些研究还揭示了这些通路之间的广泛串扰。 塑造脸型。因此，这项应用的目标是确定这些蛋白质如何单独和 作为外胚层中的一个网络来调节头面部的形成。在AIM I中，我们将使用Crect来调查 Wnt/β-catenin信号在外胚层中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Aim III中，我们将用Fgf8测试这两条通路的相互作用。结果是 这些分析将揭示这些信号通路如何相互作用来控制小鼠的颅面部 并将为面部生长和图案的调节提供重要的洞察力 研究人类先天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.