FUNCTION OF MSX2 AND TWIST IN CALVARIAL MORPHOGENESIS

这是一项研究颅缝闭合机制和颅缝闭合的病理生理学的建议，颅缝闭合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，几种基因的突变可产生颅缝闭锁综合征。我们发现同源结构域蛋白Msx2的激活突变导致波士顿型颅缝闭锁。一些研究小组已经证明FGF受体1-3的激活突变会导致Crouzon、per、Jackson-Weiss和Pfeiffer综合征。基本HLH蛋白M-twist的功能突变丧失是导致saethree - chotzen综合征的原因。尽管确定了导致颅缝闭闭的特定遗传缺陷，但这种疾病的细胞和发育机制尚不清楚。在本提案中，我们通过对Msx2和twist基因功能的研究来关注这些未解决的问题。在本提案中，我们通过分析Msx2和twist基因的功能来关注这些未解决的问题。我们的建议是基于几个关键的发现。首先，小鼠功能表型的获得和功能表型的丧失表明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头颅发育信号传导中起作用——Msx基因在BMP和可能的FGF通路中起作用，twist在FGF通路中起作用。第三，我们与Kedes小组的初步数据表明，Kedes小组表明Msx2和twist蛋白可以在物理和功能上相互作用（项目2）。这些数据是我们总体假设的基础，即Msx2通过影响头颅板和缝合线中的特定细胞群来调节头颅形态发生，这些影响是由BMP和FGF信号介导的，Msx2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突变小鼠正常颅骨发育的改变，我们将使用嵌合体分析来确定Msx2和twist在颅骨发育中所必需的组织。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之间的协同相互作用是颅骨发育所必需的假设。这项工作将提供有关颅骨发育分子遗传学的基本信息，并可能解释三种不同类型基因（Msx、fgfr和twist）的突变如何导致人类颅缝闭锁。

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.