Department of Biology, University of North Carolina-Chapel Hill, Chapel Hill, NC 27599.
Mol Biol Cell. 2021 Jul 1;32(14):1283-1292. doi: 10.1091/mbc.E20-09-0576. Epub 2021 May 19.
Many cells and tissues exhibit chirality that stems from the chirality of proteins and polymers. In the zygote, actomyosin contractility drives chiral rotation of the entire cortex circumferentially around the division plane during anaphase. How contractility is translated to cell-scale chirality, and what dictates handedness, are unknown. Septins are candidate contributors to cell-scale chirality because they anchor and cross-link the actomyosin cytoskeleton. We report that septins are required for anaphase cortical rotation. In contrast, the formin CYK-1, which we found to be enriched in the posterior in early anaphase, is not required for cortical rotation but contributes to its chirality. Simultaneous loss of septin and CYK-1 function led to abnormal and often reversed cortical rotation. Our results suggest that anaphase contractility leads to chiral rotation by releasing torsional stress generated during formin-based polymerization, which is polarized along the cell anterior-posterior axis and which accumulates due to actomyosin network connectivity. Our findings shed light on the molecular and physical bases for cellular chirality in the zygote. We also identify conditions in which chiral rotation fails but animals are developmentally viable, opening avenues for future work on the relationship between early embryonic cellular chirality and animal body plan.
许多细胞和组织表现出手性，这种手性源于蛋白质和聚合物的手性。在受精卵中，在后期，肌动球蛋白收缩力驱动整个皮层围绕着分裂面进行圆周向的手性旋转。收缩力如何转化为细胞尺度的手性，以及什么决定手性，目前尚不清楚。凝缩蛋白是细胞尺度手性的候选贡献者，因为它们锚定并交联肌动球蛋白细胞骨架。我们报告说，凝缩蛋白是后期皮层旋转所必需的。相比之下，我们发现早期后期富含后部的formin CYK-1 对于皮层旋转不是必需的，但有助于其手性。同时缺失凝缩蛋白和 CYK-1 功能会导致皮层旋转异常，通常会发生反转。我们的结果表明，后期的收缩力通过释放formin 聚合过程中产生的扭转应力来导致手性旋转，这种扭转应力沿细胞前后轴极化，并由于肌动球蛋白网络的连接而积累。我们的研究结果揭示了受精卵中细胞手性的分子和物理基础。我们还确定了手性旋转失败但动物发育正常的条件，为进一步研究早期胚胎细胞手性与动物体节计划之间的关系开辟了途径。
