Optogenetic inhibition of actomyosin reveals mechanical bistability of the mesoderm epithelium during Drosophila mesoderm invagination.
Optogenetic inhibition of actomyosin reveals mechanical bistability of the mesoderm epithelium during Drosophila mesoderm invagination.
复制标题
肌动球蛋白的光遗传抑制揭示了果蝇中胚层内陷过程中中胚层上皮的机械双稳态。
作者：
Guo H;Swan M;He B
由肌动蛋白和非肌肉肌球蛋白II（肌动球蛋白）驱动的顶端收缩提供了一个保守的机制来介导上皮折叠。目前尚不清楚如何收缩力附近的顶端表面的细胞片驱动出平面弯曲的表和是否肌球蛋白收缩性是需要在整个折叠。通过光遗传学介导的肌动球蛋白的急性抑制，我们发现在果蝇中胚层内陷期间，肌动球蛋白收缩性对于在折叠的早期“启动”阶段防止组织松弛是至关重要的，但对于组织通过定型过渡构型后的实际折叠步骤是不稳定的。这种二元反应表明果蝇中胚层在原肠胚形成过程中是机械性的。计算机建模分析表明，二进制组织的肌动球蛋白抑制反应，可以在模拟上皮细胞，经历屈曲样变形共同介导的顶端收缩中胚层和平面内压缩周围外胚层的apicobasal收缩。有趣的是，野生型和蜗牛突变体之间的比较，未能指定的中胚层表明，侧外胚层经历apicobasal收缩原肠胚独立的中胚层内陷。我们建议果蝇中胚层内陷是通过局部顶端收缩和促进上皮屈曲的上皮的机械双稳定性之间的相互作用实现的。
Apical constriction driven by actin and non-muscle myosin II (actomyosin) provides a well-conserved mechanism to mediate epithelial folding. It remains unclear how contractile forces near the apical surface of a cell sheet drive out-of-the-plane bending of the sheet and whether myosin contractility is required throughout folding. By optogenetic-mediated acute inhibition of actomyosin, we find that during Drosophila mesoderm invagination, actomyosin contractility is critical to prevent tissue relaxation during the early, ‘priming’ stage of folding but is dispensable for the actual folding step after the tissue passes through a stereotyped transitional configuration. This binary response suggests that Drosophila mesoderm is mechanically bistable during gastrulation. Computer modeling analysis demonstrates that the binary tissue response to actomyosin inhibition can be recapitulated in the simulated epithelium that undergoes buckling-like deformation jointly mediated by apical constriction in the mesoderm and in-plane compression generated by apicobasal shrinkage of the surrounding ectoderm. Interestingly, comparison between wild-type and snail mutants that fail to specify the mesoderm demonstrates that the lateral ectoderm undergoes apicobasal shrinkage during gastrulation independently of mesoderm invagination. We propose that Drosophila mesoderm invagination is achieved through an interplay between local apical constriction and mechanical bistability of the epithelium that facilitates epithelial buckling.