Zeitlinger J, Bohmann D
European Molecular Biology Laboratory (EMBL), Meyerhofstrasse 1, Heidelberg, Germany.
Development. 1999 Sep;126(17):3947-56. doi: 10.1242/dev.126.17.3947.
Dorsal closure, a morphogenetic movement during Drosophila embryogenesis, is controlled by the Drosophila JNK pathway, D-Fos and the phosphatase Puckered (Puc). To identify principles of epithelial closure processes, we studied another cell sheet movement that we term thorax closure, the joining of the parts of the wing imaginal discs which give rise to the adult thorax during metamorphosis. In thorax closure a special row of margin cells express puc and accumulate prominent actin fibres during midline attachment. Genetic data indicate a requirement of D-Fos and the JNK pathway for thorax closure, and a negative regulatory role of Puc. Furthermore, puc expression co-localises with elevated levels of D-Fos, is reduced in a JNK or D-Fos loss-of-function background and is ectopically induced after JNK activation. This suggests that Puc acts downstream of the JNK pathway and D-Fos to mediate a negative feed-back loop. Therefore, the molecular circuitry required for thorax closure is very similar to the one directing dorsal closure in the embryo, even though the tissues are not related. This finding supports the hypothesis that the mechanism controlling dorsal closure has been co-opted for thorax closure in the evolution of insect metamorphosis and may represent a more widely used functional module for tissue closure in other species as well.
背侧闭合是果蝇胚胎发育过程中的一种形态发生运动，受果蝇JNK信号通路、D-Fos和磷酸酶褶皱蛋白（Puc）控制。为了确定上皮闭合过程的原理，我们研究了另一种细胞片层运动，我们称之为胸部闭合，即翅原基盘在变态发育过程中形成成虫胸部的各部分相互连接的过程。在胸部闭合过程中，一排特殊的边缘细胞表达Puc，并在中线附着过程中积累显著的肌动蛋白纤维。遗传数据表明，胸部闭合需要D-Fos和JNK信号通路，且Puc具有负调控作用。此外，Puc的表达与D-Fos水平升高共定位，在JNK或D-Fos功能缺失背景下表达降低，在JNK激活后异位诱导表达。这表明Puc在JNK信号通路和D-Fos下游起作用，介导负反馈环。因此，胸部闭合所需的分子回路与胚胎中指导背侧闭合的分子回路非常相似，尽管这些组织并无关联。这一发现支持了这样一种假说，即在昆虫变态发育的进化过程中，控制背侧闭合的机制已被用于胸部闭合，并且可能代表了其他物种中更广泛使用的组织闭合功能模块。
