Cytokine-specific ERK signaling dynamics in human MPPs are cell-context dependent. (A) ERK signaling dynamics in single MPPs upon stimulation with 8 cytokine combinations are shown as heatmap (top panel) and time series (middle panel). For heatmaps, cells are organized according to the identified 4 clusters (nonresponder, transient, intermediate, and sustained) and sorted based on cumulative ERK signal (low to high). Heatmap heights stretched to compensate for different cell numbers analyzed and best illustrate the distribution of 4 clusters (scaled to 100%). For time series, gray curves represent individual cells, and black curve represents the population average. The 2 dashed lines denote values of 0 (bottom) and mean + 2xSD of the baseline measurements (top). Gray bar at the top indicates the timing of cytokine presence. Distributions of 4 clusters across 8 cytokine combinations (bottom panel) are calculated within individual experiments and shown as mean ± SD from 3 independent experiments (see supplemental Figure 6B for P values determined by pairwise Student t test with FDR correction). Black solid circles indicate the presence of cytokines. Number of independent experiments (N) performed and single cells (n) analyzed are shown. Two or 3 pooled UCB units were used per experiment. (B) Percentage of HSCs vs MPPs displaying different ERK signaling dynamics upon SCF stimulation (2-tailed Student t test).