MK development is restricted by SRGN^–/– conditioned media and PF4 in vitro. (A) Geometric mean fluorescence intensity (GMFI) of CD41 and CD42b staining of MKs during differentiation in either fresh media (FM), WT conditioned media (CM), or SRGN^–/– CM; n = 5. (B) The percentage of the total single-cell population collected residing with either the 2N, 4N, 8N, or 16N peak after propidium iodide staining; N = 5. (C) GMFI of CD41 and CD42b staining of MKs during differentiation in either FM or media supplemented with 50 ng/mL rPF4 on day 3. The arrow indicates treatment time point; n = 5. (D) The percentage of the total single-cell population collected residing with either the 2N, 4N, 8N, or 16N peak after propidium iodide staining; n = 5. Significance was determined by comparing each group with the corresponding WT with FM treatment. Significance: ns is indicated by P > .05; ∗P ≤ .05; ∗∗P ≤ .01; ∗∗∗P ≤ .001; ∗∗∗∗P ≤ .0001. All error bars represent the SEM. rPF4, recombinant platelet factor 4.