MOLECULAR BASIS OF TISSUE INTERACTIONS THAT REGULATE CRANIOFACIAL DEVELOPMENT

描述(申请人提供)：面部中部和上部的发育依赖于前脑、神经脊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着表面外胚层中一个信号中心(额鼻外胚层区；FEZ)的形成，该中心调节着面部中部和上部的生长和图案。此外，我们还证明，干扰FEZ的形成会产生表现为全前脑截形(HPE)的胚胎。我们的长期目标是确定调控FEZ建立的潜在分子机制(S)，并确定来自该信号中心的信号如何调控面部中部和上部的花纹生长。FEZ内的细胞表达Shh、成纤维细胞生长因子8(Fgf8)和骨形态发生蛋白(BMPS)等形态原。这些分子是调节FEZ功能的理想候选者，也可能是导致头部这一区域畸形的致畸侮辱的目标。我们假设BMPs和SHH的信号调节外胚层Shh表达的诱导，BMPS、Shh和Fgf8共同调节FEZ的功能。在我们的第一个特定目标中，我们将评估外胚层细胞中是否直接需要BMP和/或SHH信号来诱导FEZ中Shh的表达，我们将评估在没有BMP信号的情况下FEZ形成的功能后果。第二个特定目标的目的是使用组织特异性的、功能丧失的方法来研究在FEZ中表达的BMP的作用。具体地说，我们将评估下调BMP表达的形态和分子后果。在我们的第三个具体目标中，我们将评估FGF8在建立FEZ中的作用，以及FGF8在调节该信号中心功能中的作用。我们将使用遗传方法去除或减少Fgf8在小鼠胚胎的前脑和外胚层中的表达，并评估FEZ的形成。此外，为了区分Fgf8在FEZ功能中的早期和晚期作用，我们将表征一个新的嵌合系统中的每个FEZ。我们的结果将有助于全面理解调控中上面部发育的上皮-间充质相互作用，并将为理解该区域缺陷的产生提供基础。

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.