Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 2EJ, UK.
Department of Biomedical Science, The University of Sheffield, Sheffield S10 2TN, UK.
Biol Open. 2016 Apr 15;5(4):397-408. doi: 10.1242/bio.017152.
The epidermal patterns of all three larval instars (L1-L3) ofDrosophilaare made by one unchanging set of cells. The seven rows of cuticular denticles of all larval stages are consistently planar polarised, some pointing forwards, others backwards. In L1 all the predenticles originate at the back of the cells but, in L2 and L3, they form at the front or the back of the cell depending on the polarity of the forthcoming denticles. We find that, to polarise all rows, the Dachsous/Fat system is differentially utilised; in L1 it is active in the placement of the actin-based predenticles but is not crucial for the final orientation of the cuticular denticles, in L2 and L3 it is needed for placement and polarity. We find Four-jointed to be strongly expressed in the tendon cells and show how this might explain the orientation of all seven rows. Unexpectedly, we find that L3 that lack Dachsous differ from larvae lacking Fat and we present evidence that this is due to differently mislocalised Dachs. We make some progress in understanding how Dachs contributes to phenotypes of wildtype and mutant larvae and adults.
所有三个幼虫龄期（L1-L3）的果蝇表皮模式都是由一组不变的细胞形成的。所有幼虫阶段的七排表皮齿状突起始终呈平面极化，有些指向前方，有些指向后方。在 L1 中，所有的前齿原基都起源于细胞的后部，但在 L2 和 L3 中，它们在前部或后部形成，这取决于即将形成的齿状突起的极性。我们发现，为了使所有的排都极化， Dachsous/Fat 系统被不同地利用；在 L1 中，它在肌动蛋白基前齿原基的放置中是活跃的，但对表皮齿状突起的最终取向不是关键的，在 L2 和 L3 中，它是放置和极性所必需的。我们发现 Four-jointed 在腱细胞中强烈表达，并展示了这如何解释所有七排的取向。出乎意料的是，我们发现缺乏 Dachsous 的 L3 与缺乏 Fat 的幼虫不同，我们提出证据表明这是由于 Dachs 的错误定位不同。我们在理解 Dachs 如何导致野生型和突变体幼虫和成虫表型方面取得了一些进展。
