Rbm15-deficient HSC/Ps favor megakaryocytic differentiation in vivo and in vitro. (A) Increased megakaryocytes in Rbm15-KO mice. A representative flow analysis of megakaryocytes in the spleens of Rbm15-KO and -WT control mice using megakaryocyte cell surface marker CD41 is shown (i). The percentages of the CD41⁺ cells in the Mac1⁻Gr1⁻ splenic and BM populations from 4 independent experiments are shown as bar graphs (ii). Cryosections of Rbm15-WT and -KO spleens were stained for AchE. Representative images are shown (iii). (B) Quantitation of CFU-Mk colony numbers. Lin⁻ BM cells were plated in MegaCult-C medium with IL-3, IL-6, and different concentrations of TPO for CFU-Mk colony formation. The colony numbers were quantitated after a 7-day culture. The bar graph represents results from 2 independent experiments. (C) Morphology of AchE-stained CFU-Mk colonies. Representative pictures of colonies cultured with 20 ng/mL and 100 ng/mL TPO are shown. (D) Quantitation of cell number and size of AchE-positive cells in each CFU-Mk colony. Average cell number in each colony (left) and average cell size (μM³; right) are graphed. Data were collected from 2 independent experiments. Error bars indicate SD.