The University of Kansas, 1200 Sunnyside Avenue, Lawrence, KS, 66045, USA.
Evol Dev. 2013 Sep-Oct;15(5):373-84. doi: 10.1111/ede.12045.
The canonical Wnt signaling pathway is conserved in its role in axial patterning throughout Metazoa. In some hydrozoans (Phylum Cnidaria), Wnt signaling is implicated in oral-aboral patterning of the different life cycle stages-the planula, polyp and medusa. Unlike most hydrozoans, members of Aplanulata lack a planula larva and the polyp instead develops directly from a brooded or encysted embryo. The Aplanulata species Ectopleura larynx broods such embryos within gonophores. These gonophores are truncated medusae that remain attached to the polyps from which they bud, and retain evolutionary remnants of medusa structures. In E. larynx, gonophores differ between males and females in their degree of medusa truncation, making them an ideal system for examining truncated medusa development. Using next-generation sequencing, we isolated genes from Wnt signaling pathways and examined their expression in E. larynx. Our data are consistent with the Wnt pathway being involved in axial patterning of the polyp and truncated medusa. Changes in the spatial expression of Wnt pathway genes are correlated with the development of different oral structures in male and female gonophores. The absence of expression of components of the Wnt pathway and presence of a Wnt pathway antagonist SFRP in the developing anterior end of the gonophore suggest that downregulation of the Wnt pathway could play a role in medusa reduction in E. larynx.
经典 Wnt 信号通路在后生动物中轴向模式形成过程中发挥着保守作用。在一些水螅虫（刺胞动物门）中，Wnt 信号通路被认为参与了不同生命周期阶段（浮浪幼虫、水螅体和水母）的口-肛模式形成。与大多数水螅虫不同，无腔肠动物缺乏浮浪幼虫，而水螅体则直接从胎生或包囊的胚胎发育而来。无腔肠动物物种 Ectopleura larynx 在生殖巢内胎生这样的胚胎。这些生殖巢是截断的水母，仍然附着在它们萌芽的水螅体上，并保留了水母结构的进化残余物。在 E. larynx 中，生殖巢在水母截断程度上存在雌雄差异，这使它们成为研究截断水母发育的理想系统。通过下一代测序，我们从 Wnt 信号通路中分离出基因，并研究了它们在 E. larynx 中的表达。我们的数据表明，Wnt 通路参与了水螅体和截断水母的轴向模式形成。Wnt 通路基因的空间表达变化与雄雌生殖巢中不同口腔结构的发育相关。Wnt 通路成分的表达缺失和 Wnt 通路拮抗剂 SFRP 在生殖巢前端的发育存在表明，Wnt 通路的下调可能在 E. larynx 中水母减少中发挥作用。
