Molecular Analysis of the Segmentation Clock

描述(申请人提供)：我们对脊椎轴的形态发生感兴趣，尤其是对身体的变态结构的模式和分化感兴趣。在脊椎动物胚胎中，最明显的变态结构是体节，它产生身体的节段性结构，包括中轴骨骼、背部真皮和所有骨骼肌。与这一应用相关的研究的中心主题是了解一系列事件，这些事件在分子水平上调节脊椎动物胚胎身体平面的分割。我们将主要集中在几年前确定的一种名为“分段时钟”的分子振荡器的研究。这种分子钟的节律与分割的节奏平行，最初是在鸡胚胎中发现的，它是在卵裂前中胚层(PSM)中编码特定基因的mRNA脉冲。分段时钟现在已经在鱼、鸡和小鼠身上被识别出来，它控制着“循环基因”的周期性表达，到目前为止，这些基因都与Notch途径有关。目前还不清楚分段时钟的潜在机制及其在分段过程中的确切作用。关于分段时钟的分子机制，需要提出的一个主要问题是Notch信号的作用。我们的初步研究和在小鼠和鱼身上的遗传学证据表明，这一途径在控制振荡中发挥着重要作用，但目前尚不清楚它是否作用于振荡器的核心机制。该项目的一个主要目标将是在分子和细胞水平上进行实验，以表征Notch途径在振荡器功能中的作用。我们还发现，在鸡胚胎中，成纤维细胞生长因子信号控制着分割程序的激活和体细胞边界的定位。我们打算确定成纤维细胞生长因子通路的不同组成部分在这一过程中的意义，并将研究成纤维细胞生长因子信号与分段时钟的相互作用。最后，我们提供了分段钟与HOX基因在轴形成过程中的激活或维持之间耦合的证据，我们打算进一步描述这种相互作用在鸡胚胎发生过程中的特征。对节段钟功能的理解具有相当大的临床意义，因为在人类中，与这种振荡器功能相关的基因突变，如Delta-like 3(DLL3)，会导致脊柱的异常分段，类似于脊柱肋骨发育不良综合征。

DESCRIPTION (provided by applicant): We are interested in the morphogenesis of the vertebrate axis and more particularly in the patterning and differentiation of the metameric structures of the body. In the vertebrate embryo, the most overt metameric structures are the somites, which give rise to the segmented structures of the body including the axial skeleton, the dermis of the back and all skeletal muscles. The central theme of the research relevant to this application is to understand the cascade of events, which regulate the segmentation of the body plan of vertebrate embryos at the molecular level. We will essentially focus on the study of a molecular oscillator called the " Segmentation Clock" which we identified a few years ago. This molecular clock whose rhythm parallels that of segmentation was originally discovered in the chick embryo as pulses of mRNA coding for specific genes in the presomitic mesoderm (PSM). The Segmentation Clock has now been identified in fish, chick and mouse and controls the periodic expression of "Cyclic Genes " which are, so far, all related to the Notch pathway. Neither the mechanism underlying the Segmentation Clock nor its precise role in the segmentation process are currently understood. A major question to be asked regarding the molecular machinery of the Segmentation Clock concerns the role of Notch signaling. Our preliminary studies and genetic evidence in mouse and fish suggest that this pathway plays an important role in the control of the oscillations but it is not known whether it acts in the core mechanism of the oscillator. A major aim of this project will be to carry out experiments at the molecular and cellular level to characterize the role of the Notch pathway in the function of the oscillator. We also showed that FGF signaling controls the activation of the segmentation program and the positioning of somitic boundaries in the chick embryo. We intend to establish the implication of the various components of the FGF pathway in this process, and we will examine the interaction of FGF signaling with the Segmentation Clock. Finally, we have provided evidence for a coupling between the Segmentation Clock and the activation or maintenance of Hox genes during axis formation, and we intend to further characterize this interaction during chick embryogenesis. The understanding of the functioning of the Segmentation Clock is of considerable clinical relevance, since in humans mutations in the genes associated with the function of this oscillator such as delta-like 3 (dll3) result in abnormal segmentation of the vertebral column similar to that seen in the spondylocostal dysostosis syndrome.