During cytokinesis, animal cells rapidly remodel the equatorial cortex to build an aligned array of actin filaments called the contractile ring. Local reorientation of filaments by active equatorial compression is thought to underlie the emergence of filament alignment during ring assembly. Here, combining single molecule analysis and modeling in one-cell C. elegans embryos, we show that filaments turnover is far too fast for reorientation of individual filaments by equatorial compression to explain the observed alignment, even if favorably oriented filaments are selectively stabilized. By tracking single formin/CYK-1::GFP particles to monitor local filament assembly, we identify a mechanism that we call filament-guided filament assembly (FGFA), in which existing filaments serve as templates to orient the growth of new filaments. FGFA sharply increases the effective lifetime of filament orientation, providing structural memory that allows cells to build highly aligned filament arrays in response to equatorial compression, despite rapid turnover of individual filaments.

在胞质分裂过程中，动物细胞迅速重塑赤道皮层，形成排列整齐的肌动蛋白丝阵列，称为收缩环。通过主动赤道压缩对细丝进行局部重新定向被认为是环组装过程中细丝排列出现的基础。在这里，在单细胞秀丽隐杆线虫中结合单分子分析和建模胚胎，我们表明细丝周转速度太快，无法通过赤道压缩重新定向单个细丝来解释观察到的排列，即使有利定向的细丝被选择性地稳定。通过跟踪单个formin/CYK-1::GFP 粒子以监测局部细丝组装，我们确定了一种称为细丝引导细丝组装（FGFA）的机制，其中现有细丝作为模板来定向新细丝的生长。FGFA 显着增加了细丝取向的有效寿命，提供结构记忆，允许细胞构建高度对齐的细丝阵列以响应赤道压缩，尽管单个细丝的快速周转。