Data from: Single‐cell profiling screen identifies microtubule‐dependent reduction of variability in signaling

Populations of isogenic cells often respond coherently to signals, despite differences in protein abundance and cell state. Previously, we uncovered processes in the Saccharomyces cerevisiae pheromone response system (PRS) that reduced cell‐to‐cell variability in signal strength and cellular response. Here, we screened 1,141 non‐essential genes to identify 50 “variability genes”. Most had distinct, separable effects on strength and variability of the PRS, defining these quantities as genetically distinct “axes” of system behavior. Three genes affected cytoplasmic microtubule function: BIM1, GIM2, and GIM4. We used genetic and chemical perturbations to show that, without microtubules, PRS output is reduced but variability is unaffected, while, when microtubules are present but their function is perturbed, output is sometimes lowered, but its variability is always high. The increased variability caused by microtubule perturbations required the PRS MAP kinase Fus3 and a process at or upstream of Ste5, the membrane‐localized scaffold to which Fus3 must bind to be activated. Visualization of Ste5 localization dynamics demonstrated that perturbing microtubules destabilized Ste5 at the membrane signaling site. The fact that such microtubule perturbations cause aberrant fate and polarity decisions in mammals suggests that microtubule‐dependent signal stabilization might also operate throughout metazoans.尽管细胞间存在蛋白质丰度与细胞状态的差异，同基因细胞（isogenic cells）群体通常仍能对信号产生协同一致的应答。此前，我们在酿酒酵母信息素响应系统（pheromone response system, PRS）中发现了可降低信号强度与细胞应答间细胞间变异的过程。本研究针对1141个非必需基因进行筛选，最终鉴定出50个“变异基因”。其中大多数基因对PRS的信号强度与变异程度具有独立且可区分的调控效应，这表明这两个参数是系统行为中遗传上独立的“调控轴”。其中3个基因（BIM1、GIM2与GIM4）参与调控细胞质微管功能。我们通过遗传与化学扰动实验证实：当不存在微管时，PRS的输出信号会减弱但变异程度不受影响；而当微管存在但其功能受到扰动时，PRS输出信号有时会降低，但其变异程度始终处于较高水平。微管扰动所引发的变异程度升高，依赖于PRS通路中的丝裂原活化蛋白激酶Fus3（MAP kinase Fus3）以及位于Ste5（Fus3激活所需结合的膜定位支架蛋白）处或其上游的调控过程。对Ste5定位动态的可视化实验表明，微管扰动会破坏Ste5在膜信号位点的稳定性。这类微管扰动会导致哺乳动物出现异常的细胞命运与极性决定，这一现象提示，依赖微管的信号稳定机制可能同样存在于所有后生动物类群中。