Institute of Genetics, Technische Universität Dresden, 01062 Dresden, Germany.
Curr Biol. 2013 Aug 5;23(15):1472-7. doi: 10.1016/j.cub.2013.06.014. Epub 2013 Jul 3.
Whole-tissue rotations have recently been recognized as a widespread morphogenetic process important for tissue elongation [1-4]. In Drosophila ovaries, elongation of the egg chamber involves a global rotation of the follicle epithelium along the anterior-posterior axis [5]. Individual egg chambers rotate either in a clockwise or counterclockwise direction; however, how the symmetry of egg chambers is broken to allow rotation remains unknown. Here we show that at the basal side of follicle cells, microtubules are preferentially aligned perpendicular to the anterior-posterior axis of the egg chamber. Microtubule depolymerization stalls egg chamber rotation and egg chamber elongation. The preferential alignment of microtubules and egg chamber rotation depend on the atypical cadherin Fat2 and the planar polarized Fat2 localization depends on intact microtubules. Moreover, by tracking microtubule plus-end growth in vivo using EB1::GFP, we find that microtubules are highly polarized in the plane of the follicle epithelium. Polarization of microtubules precedes the onset of egg chamber rotation and predicts the direction of rotation. Our data suggest a feedback amplification mechanism between Fat2 localization and microtubule polarity involved in breaking symmetry and directing egg chamber rotation.
整体组织旋转最近被认为是一种广泛存在的形态发生过程，对于组织伸长非常重要[1-4]。在果蝇卵巢中，卵室的伸长涉及沿前后轴的滤泡上皮的全局旋转[5]。个别卵室沿顺时针或逆时针方向旋转；然而，如何打破卵室的对称性以允许旋转仍然未知。在这里，我们表明在滤泡细胞的基底侧，微管优先沿卵室的前后轴垂直排列。微管解聚会使卵室旋转和伸长停止。微管的优先排列和卵室的旋转依赖于非典型钙粘蛋白 Fat2，而 Fat2 的平面极化定位依赖于完整的微管。此外，通过使用 EB1::GFP 在体内追踪微管末端生长，我们发现微管在滤泡上皮的平面中高度极化。微管的极化先于卵室旋转的开始，并预测旋转的方向。我们的数据表明，Fat2 定位和微管极性之间的反馈放大机制参与了打破对称性和指导卵室旋转。
