Osborne Peter W, Benoit Gérard, Laudet Vincent, Schubert Michael, Ferrier David E K
Zoology Department, Oxford University, South Parks Road, Oxford, OX1 3PS, UK.
Dev Biol. 2009 Mar 1;327(1):252-62. doi: 10.1016/j.ydbio.2008.11.027. Epub 2008 Dec 7.
The ParaHox cluster is the evolutionary sister to the Hox cluster. Like the Hox cluster, the ParaHox cluster displays spatial and temporal regulation of the component genes along the anterior/posterior axis in a manner that correlates with the gene positions within the cluster (a feature called collinearity). The ParaHox cluster is however a simpler system to study because it is composed of only three genes. We provide a detailed analysis of the amphioxus ParaHox cluster and, for the first time in a single species, examine the regulation of the cluster in response to a single developmental signalling molecule, retinoic acid (RA). Embryos treated with either RA or RA antagonist display altered ParaHox gene expression: AmphiGsx expression shifts in the neural tube, and the endodermal boundary between AmphiXlox and AmphiCdx shifts its anterior/posterior position. We identified several putative retinoic acid response elements and in vitro assays suggest some may participate in RA regulation of the ParaHox genes. By comparison to vertebrate ParaHox gene regulation we explore the evolutionary implications. This work highlights how insights into the regulation and evolution of more complex vertebrate arrangements can be obtained through studies of a simpler, unduplicated amphioxus gene cluster.
ParaHox基因簇是Hox基因簇在进化上的姊妹。与Hox基因簇一样，ParaHox基因簇也显示出其组成基因沿前后轴的时空调控，这种调控方式与基因簇内的基因位置相关（这一特征称为共线性）。然而，ParaHox基因簇是一个更易于研究的系统，因为它仅由三个基因组成。我们对文昌鱼ParaHox基因簇进行了详细分析，并首次在单一物种中研究了该基因簇对单一发育信号分子视黄酸（RA）的反应调控。用RA或RA拮抗剂处理的胚胎显示出ParaHox基因表达的改变：AmphiGsx在神经管中的表达发生变化，AmphiXlox和AmphiCdx之间的内胚层边界在前后位置上发生移动。我们鉴定了几个假定的视黄酸反应元件，体外实验表明其中一些元件可能参与了ParaHox基因的RA调控。通过与脊椎动物ParaHox基因调控进行比较，我们探讨了其进化意义。这项工作突出了如何通过研究一个更简单、未重复的文昌鱼基因簇来深入了解更复杂的脊椎动物基因排列的调控和进化。
