Moline M M, Southern C, Bejsovec A
Department of Biochemistry, Molecular Biology and Cell Biology, Northwestern University, Evanston, IL 60208-3500, USA.
Development. 1999 Oct;126(19):4375-84. doi: 10.1242/dev.126.19.4375.
Active endocytotic processes are required for the normal distribution of Wingless (Wg) protein across the epidermal cells of each embryonic segment. To assess the functional consequences of this broad Wg distribution, we have devised a means of perturbing endocytosis in spatially restricted domains within the embryo. We have constructed a transgene expressing a dominant negative form of shibire (shi), the fly dynamin homologue. When this transgene is expressed using the GAL4-UAS system, we find that Wg protein distribution within the domain of transgene expression is limited and that Wg-dependent epidermal patterning events surrounding the domain of expression are disrupted in a directional fashion. Our results indicate that Wg transport in an anterior direction generates the normal expanse of naked cuticle within the segment and that movement of Wg in a posterior direction specifies diverse denticle cell fates in the anterior portion of the adjacent segment. Furthermore, we have discovered that interfering with posterior movement of Wg rescues the excessive naked cuticle specification observed in naked (nkd) mutant embryos. We propose that the nkd segment polarity phenotype results from unregulated posterior transport of Wg protein and therefore that wild-type Nkd function may contribute to the control of Wg movement within the epidermal cells of the segment.
无翅（Wg）蛋白在每个胚胎节段的表皮细胞中正常分布需要活跃的内吞作用过程。为了评估这种广泛的Wg分布的功能后果，我们设计了一种方法来干扰胚胎内空间受限区域的内吞作用。我们构建了一个转基因，它表达一种显性负性形式的发动蛋白（shi），即果蝇的发动蛋白同源物。当使用GAL4-UAS系统表达这个转基因时，我们发现转基因表达区域内的Wg蛋白分布受到限制，并且围绕表达区域的依赖Wg的表皮模式形成事件以定向方式被破坏。我们的结果表明，Wg向前运输产生节段内正常的裸露表皮区域，并且Wg向后移动决定了相邻节段前部不同的齿状细胞命运。此外，我们发现干扰Wg的向后移动可以挽救在无表皮（nkd）突变胚胎中观察到的过度裸露表皮的形成。我们提出，nkd节段极性表型是由Wg蛋白不受调控的向后运输导致的，因此野生型Nkd的功能可能有助于控制节段表皮细胞内Wg的移动。
