Hayward D C, Catmull J, Reece-Hoyes J S, Berghammer H, Dodd H, Hann S J, Miller D J, Ball E E
Research School of Biological Sciences, Australian National University, Canberra.
Dev Genes Evol. 2001 Jan;211(1):10-9. doi: 10.1007/s004270000112.
We have cloned a Hox-like gene, cnox-2Am, from a staghorn coral, Acropora millepora, an anthozoan cnidarian, and characterised its embryonic and larval expression. cnox-2Am and its orthologs in other cnidarians and Trichoplax most closely resemble the Gsx and, to a lesser extent, Hox 3/4 proteins. Developmental northern blots and in situ hybridisation are consistent in showing that cnox-2Am message appears in the planula larva shortly after the oral/aboral axis is formed following gastrulation. Expression is localised in scattered ectodermal cells with a restricted distribution along the oral/aboral body axis. They are most abundant along the sides of the cylindrical larva, rare in the oral region and absent from the aboral region. These cells, which on morphological grounds we believe to be neurons, are of two types; one tri-or multipolar near the basement membrane and a second extending projections in both directions from a mid-ectodermal nucleus. Anti-RFamide staining reveals neurons with a similar morphology to the cnox-2Am-expressing cells. However, RFamide-expressing neurons are more abundant, especially at the aboral end of the planula, where there is no cnox-2Am expression. The pattern of expression of cnox-2Am resembles that of Gsx orthologs in Drosophila and vertebrates in being expressed in a spatially restricted portion of the nervous system.
我们从鹿角珊瑚（一种珊瑚虫纲珊瑚）——多孔鹿角珊瑚中克隆了一个类Hox基因cnox - 2Am，并对其在胚胎和幼虫阶段的表达进行了特征分析。cnox - 2Am及其在其他刺胞动物和扁盘动物中的直系同源基因与Gsx最为相似，在较小程度上也与Hox 3/4蛋白相似。发育Northern印迹和原位杂交结果一致表明，cnox - 2Am的信使核糖核酸（mRNA）在原肠胚形成后口/反口轴形成不久便出现在浮浪幼虫中。其表达定位于沿口/反口体轴分布受限的散在表皮细胞中。它们在圆柱形幼虫的侧面最为丰富，在口区稀少，在反口区则不存在。基于形态学原因，我们认为这些细胞是神经元，它们有两种类型；一种是靠近基底膜的三极或多极细胞，另一种是从中表皮细胞核向两个方向延伸突起的细胞。抗RFamide染色显示出与表达cnox - 2Am的细胞形态相似的神经元。然而，表达RFamide的神经元更为丰富，尤其是在浮浪幼虫的反口端，那里没有cnox - 2Am的表达。cnox - 2Am的表达模式与果蝇和脊椎动物中Gsx直系同源基因的表达模式相似，即在神经系统的空间受限部分表达。
