FLNa deficiency induces a marked defect in proplatelet formation. (A) Immunofluorescence staining for the expression of FLNa (green), F-actin (red), and nucleus (blue) in iPSC-derived MKs from P1; scale bar = 30 μm. (B) Flow cytometry analysis of CD41a, CD42a, and CD42b expression: representative dot plot (i) and relative percentages (ii) (n = 10); histogram representative of mean fluorescence intensity for CD41a and CD42a (n = 5) and for CD42b (n = 3); paired Student t test (iii). (C) Proplatelet formation potential of patient iPSC-derived clones. At least 2 clones were assayed for each genotype, for each patient, at 2 different time points. Results are presented as mean ± standard error of the mean; unpaired Student t test with Welch’s correction was used; each point represents 1 independent experiment. (A-B) Experiments were performed at day 15 or 16 of MK differentiation. (C) Proplatelet formation was measured at days 18 and 19. (D) Representative pictures for WT and mutant proplatelet-forming MKs from P1. Immunofluorescence staining of F-actin (green) and β-tubulin (red) was performed after adhesion on fibrinogen for 24 hours. The nucleus is stained with 4′,6-diamidino-2-phenylindole (DAPI; blue); scale bar = 30 μm. *P < .05, **P < .01, ***P < .001.