MOLECULAR BASIS OF TISSUE INTERACTIONS THAT REGULATE CRANIOFACIAL DEVELOPMENT

描述（由申请人提供）：面部中部和上部的发育依赖于前脑、神经嵴间充质和表面外胚层之间的信号相互作用。我们已经确定，来自前脑的信号控制形成的信号中心（额鼻外胚层区; FEZ）的表面外胚层，调节生长和图案的中上部的脸。此外，我们证明了FEZ形成的中断产生了表现出无前脑畸形（HPE）的形式frustes胚胎。我们的长期目标是确定调节FEZ建立的潜在分子机制，并确定来自该信号中心的信号如何调节中面部和上面部的图案化生长。FEZ内的细胞表达形态发生素如Shh、成纤维细胞生长因子8（Fgf 8）和骨形态发生蛋白（Bmps）。这些分子是介导FEZ功能的理想候选者，并且可能是在头部的该区域内产生畸形的致畸性损伤的目标。我们推测，BMP和SHH调节外胚层中Shh表达的诱导，并且BMP、Shh和Fgf 8共同调节FEZ的功能。在我们的第一个具体目标中，我们将评估BMP和/或SHH信号传导是否是外胚层细胞内诱导FEZ中Shh表达所直接需要的，并且我们将评估在没有BMP信号传导的情况下FEZ形成的功能后果。第二个具体目标的目的是使用组织特异性，功能丧失的方法在禽类胚胎中检查FEZ内表达的BMPs的作用。具体而言，我们将评估敲低BMP表达的形态学和分子后果。在我们的第三个具体目标中，我们将评估Fgf 8在建立FEZ中的作用，以及Fgf 8在介导该信号中心功能中的作用。我们将使用遗传学方法来消除或减少小鼠胚胎前脑和外胚层中Fgf 8的表达，并评估FEZ的形成。此外，为了区分Fgf 8在FEZ功能中的早期和晚期作用，我们将在新的嵌合系统中表征每个FEZ。我们的研究结果将有助于全面了解上皮-间充质相互作用，调节发展的中间和上部的脸，并将提供一个基础，以了解如何在这个地区出现的缺陷。

DESCRIPTION (provided by applicant): Development of the middle and upper face rely on signaling interactions among the forebrain, the neural crest mesenchyme, and the surface ectoderm. We have determined that signals derived from the forebrain control the formation of a signaling center (Frontonasal ectodermal zone; FEZ) in the surface ectoderm that regulates growth and patterning of the middle and upper face. Further, we demonstrated that disruptions to FEZ formation produced embryos that exhibited formes frustes of Holoprosencephaly (HPE). Our long term goal is to determine the underlying molecular mechanism(s) that regulate the establishment of the FEZ and to determine how signals derived from this signaling center regulate patterned growth of the middle and upper face. Cells within the FEZ express morphogens like Shh, Fibroblast growth factor 8 (Fgf8), and Bone morphogenetic proteins (Bmps). These molecules are ideal candidates for mediating function of the FEZ and are likely targets for teratogenic insults that produce malformations within this region of the head. We hypothesize that signaling by BMPs and SHH regulate induction of Shh expression in the ectoderm, and that together, Bmps, Shh, and Fgf8 regulate function of the FEZ. In our first Specific Aim we will assess whether BMP and/or SHH signaling are directly required within the ectodermal cells for induction of Shh expression in the FEZ, and we will assess the functional consequence of FEZ formation in the absence of BMP signaling. The objective of the second Specific Aim is to examine the role of the Bmps that are expressed within the FEZ using a tissue-specific, loss-of-function approach in avian embryos. Specifically, we will assess the morphological and molecular consequence of knocking-down Bmp expression. In our third Specific Aim we will assess the role of Fgf8 in establishing the FEZ, and the role of Fgf8 in mediating the function of this signaling center. We will use genetic approaches to ablate or reduce Fgf8 expression in the forebrain and ectoderm of mouse embryos and we will assess formation of the FEZ. Additionally, to distinguish between early and late roles of Fgf8 in FEZ function, we will characterize each FEZ in a novel chimeric system. Our results will contribute to the overall understanding of the epithelial-mesenchymal interactions that regulate development of the middle and upper face and will provide a basis to understand how defects in this region arise.