School of Biological Sciences A12, University of Sydney, NSW, 2006, Australia,
Dev Genes Evol. 2014 Feb;224(1):1-11. doi: 10.1007/s00427-013-0457-5. Epub 2013 Oct 16.
Hox genes are noted for their roles in specifying axial identity in bilateral forms. In the radial echinoderms, the axis whose identity Hox genes might specify remains unclear. From the expression of Hox genes in the development of the sea urchin Holopneustes purpurescens reported here and that reported previously, we clarify the axis that might be specified by Hox genes in echinoderms. The expression of HpHox11/13 here is described at three developmental stages. The expression is around the rim of the blastopore in gastrulae, in the archenteron wall and adjacent mesoderm in early vestibula larvae, and in a patch of mesoderm close to the archenteron wall in later vestibula larvae. The retained expression of HpHox11/13 in the patch of mesoderm in the later vestibula larvae is, we suggest, indicative of a posterior or an aboral growth zone. The expression of HpHox3 at the echinoid-rudiment stage, in contrast, is in oral mesoderm beneath the epineural folds, concentrated in sites where the first three adult spines form. With the expression of HpHox5 and HpHox11/13 reported previously, the expressions here support the role of Hox genes in specifying oral-aboral identity in echinoderms. How such specification and a posterior growth zone add support to a concept of the structural homology between echinoderms and chordates is discussed.
Hox 基因以其在指定双侧形式的轴向身份中的作用而闻名。在辐射型棘皮动物中，Hox 基因可能指定的轴的身份尚不清楚。从这里和以前报道的海胆 Holopneustes purpurescens 发育过程中 Hox 基因的表达，我们阐明了 Hox 基因在棘皮动物中可能指定的轴。这里描述了 HpHox11/13 在三个发育阶段的表达。在原肠胚期，表达在胚孔边缘，在早期前庭幼虫的肠腔壁和相邻中胚层，以及在稍后的前庭幼虫中靠近肠腔壁的中胚层斑块中。我们认为，后期前庭幼虫中中胚层斑块中保留的 HpHox11/13 表达表明存在后或背生长区。相比之下，在海胆幼体阶段，HpHox3 的表达在神经褶下的口腔中胚层中，集中在形成前三个成人棘的部位。结合以前报道的 HpHox5 和 HpHox11/13 的表达，这里的表达支持 Hox 基因在指定棘皮动物的口-肛身份中的作用。这种指定和后生长区如何支持棘皮动物和脊索动物之间结构同源性的概念将进行讨论。
