Biology Department, Massachusetts Institute of Technology, Cambridge, MA, United States.
Center for Interdisciplinary Research in Biology (CIRB), Collège de France, CNRS, INSERM, Université PSL, Paris, France.
Elife. 2022 Jul 7;11:e78779. doi: 10.7554/eLife.78779.
Spindle orientation is often achieved by a complex of Partner of Inscuteable (Pins)/LGN, Mushroom Body Defect (Mud)/Nuclear Mitotic Apparatus (NuMa), Gαi, and Dynein, which interacts with astral microtubules to rotate the spindle. Cortical Pins/LGN recruitment serves as a critical step in this process. Here, we identify Pins-mediated planar cell polarized divisions in several of the mitotic domains of the early embryo. We found that neither planar cell polarity pathways nor planar polarized myosin localization determined division orientation; instead, our findings strongly suggest that Pins planar polarity and force generated from mesoderm invagination are important. Disrupting Pins polarity via overexpression of a myristoylated version of Pins caused randomized division angles. We found that disrupting forces through chemical inhibitors, depletion of an adherens junction protein, or blocking mesoderm invagination disrupted Pins planar polarity and spindle orientation. Furthermore, directional ablations that separated mesoderm from mitotic domains disrupted spindle orientation, suggesting that forces transmitted from mesoderm to mitotic domains can polarize Pins and orient division during gastrulation. To our knowledge, this is the first in vivo example where mechanical force has been shown to polarize Pins to mediate division orientation.
纺锤体的定向通常是通过 Partner of Inscuteable（Pins）/LGN、Mushroom Body Defect（Mud）/Nuclear Mitotic Apparatus（NuMa）、Gαi 和 Dynein 的复合物来实现的，它与星体微管相互作用以旋转纺锤体。皮质 Pins/LGN 的募集是这个过程的关键步骤。在这里，我们在早期胚胎的几个有丝分裂区域中发现了 Pins 介导的平面细胞极化分裂。我们发现，无论是平面细胞极性途径还是平面极化肌球蛋白的定位都不能决定分裂方向；相反，我们的发现强烈表明，Pins 的平面极性和从中胚层内陷产生的力是重要的。通过过表达 Pins 的豆蔻酰化版本来破坏 Pins 的极性会导致分裂角度随机化。我们发现，通过化学抑制剂破坏力、耗尽粘着连接蛋白或阻断中胚层内陷会破坏 Pins 的平面极性和纺锤体定向。此外，将中胚层与有丝分裂区域分离的定向消融会破坏纺锤体的定向，这表明从中胚层传递到有丝分裂区域的力可以极化 Pins 并在原肠胚形成过程中定向分裂。据我们所知，这是第一个显示机械力能够极化 Pins 以介导分裂方向的体内实例。
