Lohmann J U, Bosch T C
Zoological Institute, University of Jena, 07743 Jena, Germany.
Genes Dev. 2000 Nov 1;14(21):2771-7. doi: 10.1101/gad.830100.
One of the first steps in animal development is axis formation, during which an uneven distribution of signals and/or transcription factors results in the establishment of polarity in the embryo. Hydra, one of the simplest metazoan animals, shows characteristics of a permanent embryo. Even adult polyps have a striking capacity to regenerate, suggesting that molecular mechanisms underlying de novo pattern formation are permanently active and self regulatory. Here we show that HEADY, a short, amidated peptide, plays a central role in the specification of apical fate in this simple metazoan. The HEADY gene, whose transcripts accumulate at the apical organizing center, is required for specification of apical fate, as disruption of HEADY function by dsRNA mediated interference (RNAi) results in severe defects in head formation. Conversely, an instructive role of HEADY in head specification is demonstrated by the application of synthetic HEADY peptide, which induces formation of secondary axes with head morphology. Thus, the HEADY peptide acts as developmental switch to pattern the apical-basal axis of Hydra, providing a first insight into how initial asymmetry is specified in lower metazoan animals.
动物发育的首要步骤之一是轴的形成，在此过程中信号和/或转录因子的不均匀分布导致胚胎极性的建立。水螅是最简单的后生动物之一，具有永久胚胎的特征。即使是成年水螅息肉也具有显著的再生能力，这表明从头模式形成的分子机制一直处于活跃状态且自我调节。在这里，我们表明HEADY是一种短的、酰胺化的肽，在这种简单后生动物的顶端命运特化中起核心作用。HEADY基因的转录本在顶端组织中心积累，它是顶端命运特化所必需的，因为通过双链RNA介导的干扰（RNAi）破坏HEADY功能会导致头部形成严重缺陷。相反，合成的HEADY肽的应用证明了HEADY在头部特化中的指导作用，该肽可诱导形成具有头部形态的次生轴。因此，HEADY肽作为发育开关塑造了水螅的顶-基轴，为低等后生动物中初始不对称如何被特化提供了初步见解。
