FUNCTION OF MSX2 AND TWIST IN CALVARIAL MORPHOGENESIS

这是一项研究颅骨模式的机制和颅缝融合的病理生理学的建议，这是一种以颅骨过早融合为特征的人类发育缺陷。人类遗传学的最新发现表明，几个基因的突变可以导致颅缝早闭综合征。我们发现，同源结构域蛋白MSX2中的一个激活突变会导致波士顿型的颅缝早闭。几个研究小组已经证明，激活成纤维细胞生长因子受体1-3的突变会导致Crouzon、PER、Jackson-Weiss和Pfeiffer综合征。碱性促黄体生成素蛋白M-twist功能缺失突变是Saethre-Chotzen综合征的原因。尽管发现了导致颅缝早闭的特定遗传缺陷，但对这种疾病背后的细胞和发育机制知之甚少。在这个提案中，我们通过研究MSX2和TWIST基因的功能来关注这些悬而未决的问题。在这个提案中，我们通过分析MSX2和TWIST基因的功能来关注这些悬而未决的问题。我们的建议是基于几个重要的发现。首先，小鼠的功能获得和功能丧失表型表明，MSX2和TWIST基因在颅骨形态发生和颅骨成骨细胞分化中起着关键而复杂的作用。其次，各种研究表明，MSX和TWIST基因可能在生长因子介导的颅骨发育信号中发挥作用-MSX基因在BMP中，可能在成纤维细胞生长因子途径中，TWIST在成纤维细胞生长因子途径中。第三，我们与Kedes小组的初步数据表明，Kedes小组认为MSX2和TWIST蛋白可以在物理和功能上相互作用(项目2)。这些数据是我们整个假设的基础，即MSX2和TWIST之间的协同作用是这一调节的关键方面，MSX2和TWIST通过对颅盖板和缝合中特定细胞群的影响来调节颅骨的形态发生，这些影响是由BMP和成纤维细胞生长因子信号介导的。这些是我们的具体目标：首先，我们将更详细地记录MSX和TWIST突变小鼠的正常颅骨发育，并将使用嵌合体分析来确定哪些组织中的MSX2和TWIST是颅骨发育所必需的。第三，我们将开发MSX2和TWIST在颅骨发育中的结构功能分析。第三，我们将开发MSX2和TWIST在颅骨发育中的结构-功能分析，并最终验证MSX2和TWIST之间的协同作用是颅骨发育所必需的假设。这项工作将提供有关分子遗传学颅骨发育的基本信息，并可能解释三种不同类别的基因突变是如何在人类中产生颅突融合的。

This is a proposal to investigate mechanisms of cranial patterning and the pathophysiology of of craniosynostosis, a human developmental defect characterized by the premature fusion of calvarial bones. Recent findings in human genetics have demonstrated that mutations in several genes can produce craniosynostosis syndromes. We showed that an activating mutation in the homeodomain protein Msx2 causes craniosynostosis, Boston type. Several groups have demonstrated that activating mutations in FGF receptors 1-3 cause Crouzon, per, Jackson-Weiss, and Pfeiffer syndromes. Loss of function mutations in the basic HLH protein M-twist are responsible for Saethre-Chotzen syndrome. Despite the identification of specific genetic defects that cause craniosynostosis, the cellular an developmental mechanisms underlying this disorder re poorly understood. In this proposal, we focus on these unresolved issues through an investigation of the function of the Msx2 and twist genes. In this proposal, we focus on these unresolved issues through an analysis of the function of the Msx2 and twist genes. We based our proposal on several key findings. First, gain of function and loss of function phenotypes in the mouse suggest a critical and complex role for the Msx2 and twist genes in calvarial morphogenesis, and in the differentiation of calvarial osteogenic cells. Second, a variety of studies suggest that Msx and twist genes are likely to function in growth factor mediated signaling in calvarial development-Msx genes in the BMP and possibly FGF pathways, twist in the FGF pathway. Third, our preliminary data with the Kedes group suggest that the Kedes group suggest that the Msx2 and twist proteins can interact physically and functionally (Project 2). These data are the foundation of our overall hypothesis that Msx2 and regulate calvarial morphogenesis through effects on specific cell populations in the calvarial plates and sutures, that these effects re mediated by BMP and FGF signaling, and that a synergistic interaction between Msx2 and twist is a key aspect of this regulation. These are our specific aims: First, we will document in greater detail now normal cranial development is altered in Msx and twist mutant mice, and we will use chimera analysis to identify the tissues in which Msx2 and twist are required for calvarial development Third, we will develop structure-function assays for Msx2 and twist in calvarial development. Third, we will develop structure-function assays for Msx2 and twist in calvarial development, and ultimately test the hypothesis that a synergistic interaction between Msx2 and twist is required for calvarial development. This work will provide fundamental information about the molecular genetics calvarial development and may explain how mutations in three different classes of genes, Msx, fgfr, and twist-produce craniosynostosis in humans.