Lee J D, Treisman J E
Skirball Institute for Biomolecular Medicine and Department of Cell Biology, New York University School of Medicine, New York, NY 10016, USA.
Development. 2001 May;128(9):1519-29. doi: 10.1242/dev.128.9.1519.
The posteriorly expressed signaling molecules Hedgehog and Decapentaplegic drive photoreceptor differentiation in the Drosophila eye disc, while at the anterior lateral margins Wingless expression blocks ectopic differentiation. We show here that mutations in axin prevent photoreceptor differentiation and lead to tissue overgrowth and that both these effects are due to ectopic activation of the Wingless pathway. In addition, ectopic Wingless signaling causes posterior cells to take on an anterior identity, reorienting the direction of morphogenetic furrow progression in neighboring wild-type cells. We also show that signaling by Decapentaplegic and Hedgehog normally blocks the posterior expression of anterior markers such as Eyeless. Wingless signaling is not required to maintain anterior Eyeless expression and in combination with Decapentaplegic signaling can promote its downregulation, suggesting that additional molecules contribute to anterior identity. Along the dorsoventral axis of the eye disc, Wingless signaling is sufficient to promote dorsal expression of the Iroquois gene mirror, even in the absence of the upstream factor pannier. However, Wingless signaling does not lead to ventral mirror expression, implying the existence of ventral repressors.
在果蝇眼盘中，向后表达的信号分子刺猬蛋白（Hedgehog）和果蝇转化生长因子-β（Decapentaplegic）驱动光感受器分化，而在眼盘前侧边缘，无翅蛋白（Wingless）的表达会阻止异位分化。我们在此表明，轴蛋白（axin）的突变会阻止光感受器分化并导致组织过度生长，且这两种效应均归因于无翅蛋白信号通路的异位激活。此外，异位的无翅蛋白信号会使后部细胞获得前部特征，从而使相邻野生型细胞中形态发生沟的推进方向发生重新定向。我们还表明，果蝇转化生长因子-β和刺猬蛋白的信号传导通常会阻止前部标记物（如眼无（Eyeless））在后部的表达。维持前部眼无的表达不需要无翅蛋白信号，并且与果蝇转化生长因子-β信号结合可促进其下调，这表明还有其他分子对前部特征有贡献。在眼盘的背腹轴上，即使在上游因子篮状蛋白（pannier）缺失的情况下，无翅蛋白信号也足以促进易洛魁族基因镜像（mirror）的背侧表达。然而，无翅蛋白信号不会导致镜像基因在腹侧表达，这意味着存在腹侧抑制因子。
