Establishment of Hox vertebral identities in the embryonic spine precursors.
Establishment of Hox vertebral identities in the embryonic spine precursors.
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DOI：
10.1016/s0070-2153(09)88007-1
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发表时间：
2009
影响因子：
--
通讯作者：
Pourquié O
中科院分区：
文献类型：
--
作者：
Iimura T;Denans N;Pourquié O
脊椎动物的脊柱具有两个显着的特征。第一个是它的元素-椎骨-沿前后轴沿着的周期性排列。这种分段的组织是在器官发生期间发生的体节发生的结果。分裂机制包括一个分子振荡器--分裂时钟--它提供一个周期性的信号来控制体节的产生。在胚胎轴伸长过程中，该信号被移动信号梯度系统-波前-向后移位，该波前依赖于Wnt、FGF和视黄酸途径。脊柱的另一个特征是将椎骨组细分为解剖学区域，例如颈、胸、腰、骶和尾区域。这种轴向区域化由一组称为Hox基因的转录因子控制。Hox基因在体节中表现出嵌套的表达结构域，这反映了它们沿染色体沿着的线性排列-一种称为共线性的性质。Hox基因表达结构域的共线分布为未来脊椎区域的区域化提供了蓝图。Hox基因在上胚层的体节前体中以时间共线顺序被激活，并被提出控制它们向新生近轴中胚层的渐进性侵入。因此，Hox基因的表达结构域沿前后轴的沿着定位在很大程度上受原肠胚形成期间Hox激活的时间控制。随后，通过与体细胞前中胚层中的分割机制的串扰来细化体细胞Hox结构域的定位。在这篇综述中，我们专注于我们目前的理解，建立脊椎动物发育过程中的脊椎身份的胚胎机制。
The vertebrate spine exhibits two striking characteristics. The first one is the periodic arrangement of its elements – the vertebrae – along the antero-posterior axis. This segmented organization is the result of somitogenesis, which takes place during organogenesis. The segmentation machinery involves a molecular oscillator – the segmentation clock – which delivers a periodic signal controlling somite production. During embryonic axis elongation, this signal is displaced posteriorly by a system of traveling signaling gradients – the wavefront – which depends on the Wnt, FGF and retinoic acid pathways. The other characteristic feature of the spine is the subdivision of groups of vertebrae into anatomical domains, such as the cervical, thoracic, lumbar, sacral and caudal regions. This axial regionalization is controlled by a set of transcription factors called Hox genes. Hox genes exhibit nested expression domains in the somites which reflect their linear arrangement along the chromosomes– a property termed colinearity. The colinear disposition of Hox genes expression domains provides a blueprint for the regionalization of the future vertebral territories of the spine. In amniotes, Hox genes are activated in the somite precursors of the epiblast in a temporal colinear sequence and they were proposed to control their progressive ingression into the nascent paraxial mesoderm. Consequently, the positioning of the expression domains of Hox genes along the antero-posterior axis is largely controlled by the timing of Hox activation during gastrulation. Positioning of the somitic Hox domains is subsequently refined through a cross talk with the segmentation machinery in the presomitic mesoderm. In this review, we focus on our current understanding of the embryonic mechanisms that establish vertebral identities during vertebrate development.