Department of Mechanical Engineering, Columbia University, New York, New York.
Department of Mechanical Engineering, Columbia University, New York, New York.
Biophys J. 2021 Oct 5;120(19):4214-4229. doi: 10.1016/j.bpj.2021.06.041. Epub 2021 Jul 20.
Distinct patterns of actomyosin contractility are often associated with particular epithelial tissue shape changes during development. For example, a planar-polarized pattern of myosin II localization regulated by Rho1 signaling during Drosophila body axis elongation is thought to drive cell behaviors that contribute to convergent extension. However, it is not well understood how specific aspects of a myosin pattern influence the multiple cell behaviors, including cell intercalation, cell shape changes, and apical cell area fluctuations, that simultaneously occur during morphogenesis. Here, we developed two optogenetic tools, optoGEF and optoGAP, to activate or deactivate Rho1 signaling, respectively. We used these tools to manipulate myosin patterns at the apical side of the germband epithelium during Drosophila axis elongation and analyzed the effects on contractile cell behaviors. We show that uniform activation or inactivation of Rho1 signaling across the apical surface of the germband is sufficient to disrupt the planar-polarized pattern of myosin at cell junctions on the timescale of 3-5 min, leading to distinct changes in junctional and medial myosin patterns in optoGEF and optoGAP embryos. These two perturbations to Rho1 activity both disrupt axis elongation and cell intercalation but have distinct effects on cell area fluctuations and cell packings that are linked with changes in the medial and junctional myosin pools. These studies demonstrate that acute optogenetic perturbations to Rho1 activity are sufficient to rapidly override the endogenous planar-polarized myosin pattern in the germband during axis elongation. Moreover, our results reveal that the levels of Rho1 activity and the balance between medial and junctional myosin play key roles not only in organizing the cell rearrangements that are known to directly contribute to axis elongation but also in regulating cell area fluctuations and cell packings, which have been proposed to be important factors influencing the mechanics of tissue deformation and flow.
肌动球蛋白收缩的不同模式通常与发育过程中特定上皮组织形状变化有关。例如，在果蝇体轴伸长过程中，由 Rho1 信号调节的肌球蛋白 II 定位的平面极化模式被认为驱动了有助于趋同延伸的细胞行为。然而，人们尚不清楚肌球蛋白模式的特定方面如何影响多种细胞行为，包括细胞插入、细胞形状变化和顶端细胞面积波动，这些行为同时发生在形态发生过程中。在这里，我们开发了两种光遗传学工具，即 optoGEF 和 optoGAP，分别用于激活或失活 Rho1 信号。我们使用这些工具在果蝇轴伸长过程中操纵胚带上皮细胞的顶端侧的肌球蛋白模式，并分析了对收缩细胞行为的影响。我们表明，在胚带的顶端表面上均匀地激活或失活 Rho1 信号足以在 3-5 分钟的时间尺度上破坏细胞连接处的平面极化肌球蛋白模式，导致 optoGEF 和 optoGAP 胚胎中连接和中间肌球蛋白模式的明显变化。这两种对 Rho1 活性的扰动都破坏了轴伸长和细胞插入，但对与中间和连接肌球蛋白池变化相关的细胞面积波动和细胞堆积有不同的影响。这些研究表明，急性光遗传学对 Rho1 活性的扰动足以在轴伸长过程中迅速覆盖胚带中内源性平面极化肌球蛋白模式。此外，我们的结果表明，Rho1 活性水平和中间与连接肌球蛋白之间的平衡不仅在组织变形和流动的力学中被认为直接有助于轴伸长的细胞重排的组织中发挥关键作用，而且在调节细胞面积波动和细胞堆积中发挥关键作用，这些波动和堆积被认为是影响组织变形和流动的力学的重要因素。
