Department of Systems Biology, Harvard Medical School, Boston, Massachusetts, United States of America.
PLoS One. 2010 Dec 21;5(12):e15724. doi: 10.1371/journal.pone.0015724.
Variability in cell-to-cell behavior within clonal populations can be attributed to the inherent stochasticity of biochemical reactions. Most single-cell studies have examined variation in behavior due to randomness in gene transcription. Here we investigate the mechanism of cell fate choice and the origin of cell-to-cell variation during mitotic arrest, when transcription is silenced. Prolonged mitotic arrest is commonly observed in cells treated with anti-mitotic drugs. Cell fate during mitotic arrest is determined by two alternative pathways, one promoting cell death, the other promoting cyclin B1 degradation, which leads to mitotic slippage and survival. It has been unclear whether these pathways are mechanistically coupled or independent. In this study we experimentally uncoupled these two pathways using zVAD-fmk to block cell death or Cdc20 knockdown to block slippage. We then used time-lapse imaging to score the kinetics of single cells adopting the remaining fate. We also used kinetic simulation to test whether the behaviors of death versus slippage in cell populations where both pathways are active can be quantitatively recapitulated by a model that assumes stochastic competition between the pathways. Our data are well fit by a model where the two pathways are mechanistically independent, and cell fate is determined by a stochastic kinetic competition between them that results in cell-to-cell variation.
克隆群体中细胞间行为的可变性可以归因于生化反应的固有随机性。大多数单细胞研究都检查了由于基因转录随机性而导致的行为变化。在这里，我们研究了有丝分裂停滞期间细胞命运选择的机制和细胞间变异的起源，此时转录被沉默。有丝分裂停滞是在用抗有丝分裂药物处理的细胞中常见的现象。有丝分裂停滞期间的细胞命运由两种替代途径决定，一种促进细胞死亡，另一种促进细胞周期蛋白 B1 的降解，这导致有丝分裂滑溜和存活。这些途径是否在机制上是偶联的还是独立的尚不清楚。在这项研究中，我们使用 zVAD-fmk 阻断细胞死亡或 Cdc20 敲低阻断滑溜来实验性地分离这两种途径。然后，我们使用延时成像来评分采用剩余命运的单个细胞的动力学。我们还使用动力学模拟来测试在两条途径都活跃的细胞群体中，死亡与滑溜的行为是否可以通过假设途径之间存在随机竞争的模型来定量再现。我们的数据很好地符合这样一种模型，即两条途径在机制上是独立的，细胞命运由它们之间的随机动力学竞争决定，从而导致细胞间的变异。
