FUNCTION OF MSX2 AND TWIST IN CALVARIAL MORPHOGENESIS

这是一个研究颅纹形成机制和脑缺血的病理生理学的建议。 颅缝早闭症，一种人类发育缺陷，特征是颅骨过早融合。人类遗传学的最新发现表明，几个基因的突变可以产生颅缝早闭综合征。我们发现同源异型域蛋白Msx 2的激活突变导致波士顿型颅缝早闭。几个研究小组已经证明，FGF受体1-3中的激活突变导致Crouzon、per、Jackson-Weiss和Pfeiffer综合征。基础HLH蛋白M-twist中的功能缺失突变是Saethre-Chotzen综合征的原因。尽管已经确定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。在这个建议中，我们专注于这些悬而未决的问题，通过调查Msx 2和扭曲基因的功能。在本研究中，我们通过对Msx 2和twist基因功能的分析，来关注这些尚未解决的问题。我们的建议基于几个关键的发现。首先，小鼠的功能获得和功能表型丧失表明Msx 2和twist基因在颅骨形态发生和颅骨成骨细胞分化中具有关键和复杂的作用。其次，各种研究表明，Msx和twist基因可能在颅骨发育中的生长因子介导的信号传导中起作用-Msx基因在BMP和可能的FGF途径中，twist在FGF途径中。第三，我们与Kedes小组的初步数据表明，Kedes小组认为Msx 2和twist蛋白可以在物理和功能上相互作用（项目2）。这些数据是我们总体假设的基础，即Msx 2通过对颅骨板和缝中特定细胞群的作用来调节颅骨形态发生，这些作用由BMP和FGF信号传导介导，并且Msx 2和Twist之间的协同相互作用是这种调节的关键方面。 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发生的改变，我们将使用嵌合体分析来鉴定颅骨发育所需的Msx 2和twist组织。第三，我们将开发Msx 2和twist在颅骨发育中的结构-功能测定。第三，我们将开发Msx 2和扭转在颅骨发育的结构-功能测定，并最终测试的假设，Msx 2和扭转之间的协同作用是颅骨发育所需的。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型的基因Msx，fgfr和twist突变如何在人类中产生颅缝早闭。

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.