Department of Zoology, University of Cambridge, Downing Street, Cambridge CB2 3EJ, UK.
Open Biol. 2020 Dec;10(12):200290. doi: 10.1098/rsob.200290. Epub 2020 Dec 9.
We investigate planar cell polarity (PCP) in the larval epidermis. The intricate pattern of denticles depends on only one system of PCP, the Dachsous/Fat system. Dachsous molecules in one cell bind to Fat molecules in a neighbour cell to make intercellular bridges. The disposition and orientation of these Dachsous-Fat bridges allows each cell to compare two neighbours and point its denticles towards the neighbour with the most Dachsous. Measurements of the amount of Dachsous reveal a peak at the back of the anterior compartment of each segment. Localization of Dachs and orientation of ectopic denticles help reveal the polarity of every cell. We discuss whether these findings support our gradient model of Dachsous activity. Several groups have proposed that Dachsous and Fat fix the direction of PCP via oriented microtubules that transport PCP proteins to one side of the cell. We test this proposition in the larval cells and find that most microtubules grow perpendicularly to the axis of PCP. We find no meaningful bias in the polarity of microtubules aligned close to that axis. We also reexamine published data from the pupal abdomen and find no evidence supporting the hypothesis that microtubular orientation draws the arrow of PCP.
我们研究了幼虫表皮中的平面细胞极性 (PCP)。齿突的复杂图案仅依赖于一个 PCP 系统，即 Dachsous/Fat 系统。一个细胞中的 Dachsous 分子与相邻细胞中的 Fat 分子结合形成细胞间桥。这些 Dachsous-Fat 桥的排列和方向允许每个细胞比较两个相邻细胞，并将其齿突指向 Dachsous 最多的那个邻居。对 Dachsous 含量的测量显示，在每个节段前区的后部有一个峰值。Dachs 的定位和异位齿突的取向有助于揭示每个细胞的极性。我们讨论了这些发现是否支持我们的 Dachsous 活性梯度模型。几个小组提出，Dachsous 和 Fat 通过定向微管固定 PCP 的方向，将 PCP 蛋白运送到细胞的一侧。我们在幼虫细胞中测试了这一假设，发现大多数微管垂直于 PCP 的轴生长。我们没有发现与该轴对齐的微管极性有任何有意义的偏差。我们还重新检查了来自蛹腹的已发表数据，没有发现任何证据支持微管取向绘制 PCP 箭头的假设。
