Adler P N, Liu J, Charlton J
Biology Department and Cancer Center, University of Virginia, Charlottesville, Virginia 22903, USA.
Genesis. 2000 Oct;28(2):82-91. doi: 10.1002/1526-968x(200010)28:2<82::aid-gene60>3.0.co;2-z.
Almost all epidermal cells on the Drosophila wing produce a single cuticular hair. This is formed in the pupae from a microvillus-like cell projection called the prehair. Previous experiments have shown the existence of two mechanisms that ensure that only a single hair is made. One is the restriction of prehair initiation to a small subregion of the cell by the action of the frizzled tissue polarity pathway. The second is a system that ensures the integrity of the prehair. Mutations and drugs that inhibit the actin cytoskeleton lead to the splitting of a single prehair into multiple smaller hairs. We report that large polyploid cells produce multiple hairs both because they form multiple independent prehair initiation centers and because the larger than normal hairs these cells produce have a tendency to split. We show that reducing cell size by starvation partially suppresses the phenotype seen in polyploid cells and that increasing apical cell surface area by mechanical stretching also results in the formation of multiple prehair initiation centers. We also show that the frizzled tissue polarity pathway is functional in large polyploid cells even if it is unable to restrict prehair initiation to a small region of the cell. We conclude that both of these cellular systems are limited in their ability to scale to accommodate larger cell size.
果蝇翅膀上几乎所有的表皮细胞都只产生一根表皮毛。这根表皮毛在蛹期由一种称为前毛的微绒毛状细胞突起形成。先前的实验已经表明存在两种确保只产生一根毛的机制。一种是通过卷曲蛋白组织极性途径的作用，将前毛起始限制在细胞的一个小亚区域。第二种是确保前毛完整性的系统。抑制肌动蛋白细胞骨架的突变和药物会导致单根前毛分裂成多根较小的毛。我们报告称，大型多倍体细胞会产生多根毛，这既是因为它们形成了多个独立的前毛起始中心，也是因为这些细胞产生的比正常毛发更大的毛发有分裂的倾向。我们表明，通过饥饿减小细胞大小可部分抑制多倍体细胞中出现的表型，并且通过机械拉伸增加顶端细胞表面积也会导致形成多个前毛起始中心。我们还表明，卷曲蛋白组织极性途径在大型多倍体细胞中是有功能的，即使它无法将前毛起始限制在细胞的一个小区域。我们得出结论，这两种细胞系统在适应更大细胞大小的扩展能力方面都受到限制。
