L-plastin identified as a candidate target of miR-125a-5p. (A) Predicted mRNA targets of miR-125a-5p were identified (total, 8878). (B) Heat map displaying differential gene-expression patterns of CD61-purified cultured MKs during differentiation for day 6 (D6) vs day 13 (D13) (n = 3 independent cords). Only mRNAs that showed downregulation during MK differentiation (total, 2075) were further considered. (C) Volcano plot shows platelet mRNA association with human platelet count. Only 27 mRNAs (red dots, some data points are superimposed) that were negatively associated with platelet count (adjusted P < .05) were considered. (D) Intersection of candidate targets from panels A-C. (E) Plot of Pearson correlation (R) between platelet count and LCP1 mRNA levels. Dotted lines, 95% confidence intervals. (F-G) Representative images of day 14 cultured MKs. Scale bar, 10 μm. (F) Brightfield and (G) L-plastin (green) and 4′,6-diamidino-2-phenylindole (DAPI), a nuclear stain (cyan) in round MK and PPs. (H) Representative immunoblot shows L-plastin protein levels in CD34⁺ cord blood–derived MK cultures at days 6, 9, and 14. GAPDH, glyceraldehyde-3-phosphate dehydrogenase.