PDF(Pubmed)
Abstract：
Hydra head formation depends on an organizing center in which Wnt/β-catenin signaling, that plays an inductive role, positively regulates Sp5 and Zic4, with Sp5 limiting Wnt3/β-catenin expression and Zic4 triggering tentacle formation. Using transgenic lines in which the HySp5 promoter drives eGFP expression in either the epidermis or gastrodermis, we show that Sp5 promoter activity is differentially regulated in each epithelial layer. In intact animals, epidermal HySp5:GFP activity is strong apically and weak along the body column, while in the gastrodermis, it is maximal in the tentacle ring region and maintained at a high level along the upper body column. During apical regeneration, HySp5:GFP is activated early in the gastrodermis and later in the epidermis. Alsterpaullone treatment induces a shift in apical HySp5:GFP expression towards the body column where it forms transient circular figures in the epidermis. Upon β-catenin(RNAi), HySp5:GFP activity is down-regulated in the epidermis while bud-like structures expressing HySp5:GFP in the gastrodermis develop. Sp5(RNAi) reveals a negative Sp5 autoregulation in the epidermis, but not in the gastrodermis. These differential regulations in the epidermis and gastrodermis highlight the distinct architectures of the Wnt/β-catenin/TCF/Sp5/Zic4 network in the hypostome, tentacle base and body column of intact animals, as well as in the buds and apical and basal regenerating tips.
摘要：
Hydra头的形成取决于Wnt/β-catenin信号传导的组织中心，起到诱导作用，正向调节Sp5和Zic4，Sp5限制Wnt3/β-catenin表达，Zic4触发触手形成。使用HySp5启动子驱动表皮或胃真皮中eGFP表达的转基因品系，我们显示Sp5启动子活性在每个上皮层中受到差异调节。在完整的动物中，表皮HySp5：GFP活性在顶部很强，沿身体柱较弱，而在胃真皮中，在触手环区域最大，并沿上身柱保持在较高水平。在根尖再生过程中，HySp5:GFP在胃层早期和表皮中被激活。Alsterpaullone治疗诱导根尖HySp5：GFP表达向体柱的转移，在体柱中在表皮中形成短暂的圆形图形。在β-连环蛋白（RNAi）时，HySp5:GFP活性在表皮中下调,而表达HySp5:GFP的芽样结构在胃真皮中发育。Sp5（RNAi）揭示了表皮中Sp5的负自动调节，但不是在胃皮里.表皮和胃真皮中的这些差异调节突出了子宫中Wnt/β-catenin/TCF/Sp5/Zic4网络的独特结构，完整动物的触手基部和身体柱，以及芽和顶端和基部再生尖端。
