Phylogenetic correspondence of the body axes in bilaterians is revealed by the right-sided expression of Pitx genes in echinoderm larvae
Phylogenetic correspondence of the body axes in bilaterians is revealed by the right-sided expression of Pitx genes in echinoderm larvae
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DOI：
10.1111/j.1440-169x.2006.00892.x
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发表时间：
2006-12-01
影响因子：
2.5
通讯作者：
Amemiya, Shonan
中科院分区：
文献类型：
--
作者：
Hibino, Taku;Nishino, Atsuo;Amemiya, Shonan
脊索动物和棘皮动物是三个主要的后口动物门中的两个，并且显示出明显的左右（LR）不对称性。LR不对称性的建立已经在脊椎动物中进行了探索，但在棘皮动物中基本上是未知的。在这里，我们报告的基因的表达模式，是orthopathic的脊索动物左侧的特定基因Pitx，克隆的海胆Hemicentrotus pulcherrimus（HpPitx）和海星海星（ApPitx）。HpPitch转录本首次检测到双边在一个细胞的腹外侧初级间充质细胞聚集的早期棱镜幼虫。新的表达被检测到不对称的右侧对应的双边对中胚层体腔袋和右外胚层。在海星bipinnaria幼虫中，ApPitx信号被检测到在右体腔袋和外胚层的右半部分沿着纤毛带。这些结果表明，Pitx在建立LR不对称性的功能是在棘皮动物和脊索动物的最后共同祖先中引入的。然而，右侧的具体表达棘皮动物幼虫相比，脊索动物胚胎倒置。这表明LR轴在棘皮动物和脊索动物之间呈反比，这支持了背腹轴倒置通过颠倒引入脊索动物谱系的情况。
Chordates and echinoderms are two of the three major deuterostome phyla and show conspicuous left-right (LR) asymmetry. The establishment of LR asymmetry has been explored in vertebrates, but is largely unknown in echinoderms. Here, we report the expression pattern of genes that are orthologous to the chordate left-side specific gene Pitx, cloned from the sea urchin Hemicentrotus pulcherrimus (HpPitx) and the starfish Asterina pectinifera (ApPitx). HpPitx transcripts were first detected bilaterally in one cell of the ventrolateral primary mesenchyme-cell aggregate of early prism larvae. New expression was detected asymmetrically in the right counterpart of a bilateral pair of mesodermal coelomic pouches and in the right ectoderm. In starfish bipinnaria larvae, the ApPitx signal was detected in the right coelomic pouch and in the right half of the ectoderm along the ciliary bands. These results suggest that the function of Pitx in establishing LR asymmetry was introduced in the last common ancestor of echinoderms and chordates. However, the right-side specific expression in echinoderm larvae is inverted compared to chordate embryos. This indicates that the LR axis is inversely represented between echinoderms and chordates, which supports the scenario that dorsoventral axis inversion was introduced into the chordate lineage by turning upside down.