Molecular Analysis of the Segementation Clock

描述（由申请人提供）：脊椎动物体建立在一个超聚组织上，该组织由沿前后（AP）轴的功能等效单元组成，每个单元包括椎体，其相关肌肉，周围神经和血管。然而，这些单位并不是沿着轴线严格相等的，而是沿着不同的解剖域表现出区域化。我们研究的目的是了解这种复杂的模式是如何在胚胎发生过程中建立起来的。由于脊柱复杂的神经和肌肉骨骼解剖结构，人类先天性椎体畸形是一个主要的治疗挑战。了解控制躯体/椎体模式的遗传和发育机制对预防这些出生缺陷将是无价的。椎骨的分段分布源于胚胎体早期的异聚模式，其产生与分子振荡器（即分段时钟）有关。在Hox基因的影响下，胚胎体的衍生物随后被区域化，从而在身体轴上形成不同的解剖结构域。在这项资助中，我们建议继续我们对鸡胚胎体轴的片段模式和随后的区域化的研究。我们将重点讨论三个相关问题。在Aim 1中，我们将继续对分割过程和相关振荡器进行表征。在小鼠胚胎中进行的初步微阵列研究揭示了振荡器比我们预期的要复杂得多。这导致我们重新考虑我们的分割时钟机制的研究方法。我们建议在Aim1中进一步整合，并在正常和各种实验条件下完成鸡切分时钟和近轴中胚层成熟的微阵列研究。我们将利用这些实验来重建基因网络，以帮助确定时钟机制中的关键参与者。在Aim 2中，我们将研究从原始条纹中的祖细胞产生旁轴中胚层的细节，特别关注产生该组织部分的干细胞。我们将继续研究Hox基因在近轴中胚层区域化中的作用。我们最近的研究结果表明，Hox基因控制着近轴中胚层前体从外胚层进入原始条纹的过程。在目标3中，我们将尝试了解由Hox基因控制的细胞入侵的分子和细胞方面。通过这些研究，我们期望对中胚层发育早期阶段的分割时钟机制和Hox基因功能的理解有重要的见解。

DESCRIPTION (provided by applicant): The vertebrate body is built on a metameric organization which consists of a repetition along the antero- posterior (AP) axis of functionally equivalent units, each comprising a vertebra, its associated muscles, peripheral nerves and blood vessels. These units are not, however, strictly equivalent along the axis and exhibit regionalization along the different anatomical domains. The goal of our research is to understand how this complex pattern is established during embryogenesis. Congenital vertebral malformations in humans represent a major therapeutic challenge due to the intricate neural and musculoskeletal anatomy of the spine. Understanding the genetic and developmental mechanisms which control somitic/vertebral patterning would be invaluable towards prevention of these birth defects. The segmented distribution of the vertebrae derives from the earlier metameric pattern of the embryonic somites whose production has been linked to a molecular oscillator, the segmentation clock. Under the influence of Hox genes, the derivatives of the embryonic somites become subsequently regionalized to contribute to the different anatomical domains along the body axis. In this grant, we propose to continue our studies on the segmental patterning and on the subsequent regionalization of the body axis in the chicken embryo. We will focus on three related issues. In Aim 1, we will continue our characterization of the segmentation process and of the associated oscillator. Preliminary microarray studies in the mouse embryo have revealed a far greater complexity of the oscillator than we anticipated. This led us to reconsider our approach of the study of the segmentation clock mechanism. We propose to move to a more integrated level in Aim1 and to complete a microarray study of the chicken segmentation clock and of the paraxial mesoderm maturation in normal and in various experimental conditions. We will use these experiments to reconstruct genetic networks that could help identify key players in the clock mechanism. In Aim 2, we will investigate the details of the production of the paraxial mesoderm from its progenitors in the primitive streak with a particular focus on the stem cells which generate part of this tissue. We will continue our studies of the role of Hox genes in paraxial mesoderm regionalization. Our recent results show that Hox genes control the ingression of precursors of paraxial mesoderm from the epiblast into the primitive streak. In Aim 3, we will try to understand the molecular and cellular aspects of cell ingression which are controlled by Hox genes. From these studies, we expect to gain significant insights into our understanding of the segmentation clock mechanism and of Hox gene function in early stages of mesoderm patterning.