MOLECULAR BASIS OF TISSUE INTERACTIONS THAT REGULATE CRANIOFACIAL DEVELOPMENT

描述（申请人提供）：中上部面部的发育依赖于前脑、神经嵴间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外胚层表面信号中心（额鼻外胚层区；FEZ）的形成，该信号中心调节中上部面部的生长和图案。此外，我们证明了FEZ形成的破坏产生的胚胎表现出holoproencephaly （HPE）的形式。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上部面部的模式生长。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）等形态因子。这些分子是介导FEZ功能的理想候选者，并且可能是在头部该区域产生畸形的致畸损伤的目标。我们假设BMPs和SHH的信号传导调节了外胚层SHH表达的诱导，并且BMPs、SHH和Fgf8共同调节FEZ的功能。在我们的第一个特异性目标中，我们将评估在FEZ中诱导SHH表达是否直接需要外胚细胞内的BMP和/或SHH信号，并且我们将评估在缺乏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，功能丧失方法在禽胚胎中检查FEZ内表达的bmp的作用。具体来说，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Fgf8在建立自由经济区中的作用，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在小鼠胚胎前脑和外胚层的表达，我们将评估FEZ的形成。此外，为了区分Fgf8在FEZ功能中的早期和晚期作用，我们将在一个新的嵌合系统中描述每个FEZ。我们的研究结果将有助于全面了解调节面部中部和上部发育的上皮-间充质相互作用，并将为理解该区域的缺陷如何产生提供基础。

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.