PDF(Pubmed)
Abstract：
The polygonal shape of cells in proliferating epithelia is a result of the tensile forces of the cytoskeletal cortex and packing geometry set by the cell cycle. In the larval Drosophila epidermis, two cell populations, histoblasts and larval epithelial cells, compete for space as they grow on a limited body surface. They do so in the absence of cell divisions. We report a striking morphological transition of histoblasts during larval development, where they change from a tensed network configuration with straight cell outlines at the level of adherens junctions to a highly folded morphology. The apical surface of histoblasts shrinks while their growing adherens junctions fold, forming deep lobules. Volume increase of growing histoblasts is accommodated basally, compensating for the shrinking apical area. The folded geometry of apical junctions resembles elastic buckling, and we show that the imbalance between the shrinkage of the apical domain of histoblasts and the continuous growth of junctions triggers buckling. Our model is supported by laser dissections and optical tweezer experiments together with computer simulations. Our analysis pinpoints the ability of histoblasts to store mechanical energy to a much greater extent than most other epithelial cell types investigated so far, while retaining the ability to dissipate stress on the hours time scale. Finally, we propose a possible mechanism for size regulation of histoblast apical size through the lateral pressure of the epidermis, driven by the growth of cells on a limited surface. Buckling effectively compacts histoblasts at their apical plane and may serve to avoid physical harm to these adult epidermis precursors during larval life. Our work indicates that in growing nondividing cells, compressive forces, instead of tension, may drive cell morphology.
摘要：
增殖上皮中细胞的多边形形状是细胞骨骼皮质的张力和细胞周期设定的堆积几何形状的结果。在幼体果蝇表皮中，两个细胞群，组织细胞和幼虫上皮细胞，当它们在有限的身体表面生长时争夺空间。它们在没有细胞分裂的情况下这样做。我们报道了幼虫发育过程中组织母细胞的惊人形态转变，它们从在粘附连接水平上具有笔直细胞轮廓的紧张网络构型变为高度折叠的形态。组织母细胞的顶端表面收缩，而它们生长的粘附体接合处折叠，形成深的小叶。生长中的成组织细胞的体积增加被基底容纳，补偿根尖面积的收缩。顶端连接的折叠几何形状类似于弹性屈曲，我们表明，组织母细胞顶端结构域的收缩与连接的持续增长之间的不平衡会触发屈曲。我们的模型得到了激光解剖和光学镊子实验以及计算机模拟的支持。我们的分析确定了组织细胞储存机械能的能力比迄今为止研究的大多数其他上皮细胞类型要大得多。同时保留在小时时间尺度上消散压力的能力。最后,我们提出了一种可能的机制，通过表皮的侧向压力来调节组织细胞顶端的大小，由细胞在有限表面上的生长驱动。屈曲可有效地在其顶端平面上压实组织母细胞，并可避免在幼虫生命期间对这些成年表皮前体造成身体伤害。我们的工作表明，在生长的非分裂细胞中，压缩力，而不是紧张，可以驱动细胞形态。
