Psip1 knockout affects colony formation potential of HSC in vitro. (A) Number of colonies in 3 consecutive rounds of a myeloid CFU assay per 10⁴ lin⁻ BM cells harvested from Psip^Fl/Fl and Psip^Vav/Vav mice (10 weeks of age). (B) Pre-B CFU assays for Psip^Fl/Fl and Psip^Vav/Vav cells. Lin⁻ cells and spleen cells were harvested and plated in methylcellulose for 7 to 10 days. The number of colonies formed was normalized to the control (Psip^Fl/Fl) cells. (C) qRT-PCR measuring expression levels (normalized to Gapdh) of different genes in lin⁻ cells harvest from Psip^Fl/Fl or Psip^Vav/Vav cells (before first plating) and after 1 round in myeloid CFU assay (after first plating). (D) Comparison of cell morphology of Psip^Fl/Fl and Psip^Vav/Vav cells after 1 round in the CFU assay via May-Grünwald Giemsa staining. A representative picture is shown. (E) FACS analysis for Gr-1 expression in Psip^Fl/Fl and Psip^Vav/Vav cells (n = 8) harvested after 1 round in CFU assay. Mean and SEM values are indicated. Error bars (panels A, B, C, and E) represent standard deviation of triplicate measurements. Statistical differences were determined using Student t test; *P < .05, **P < .01, ***P < .001.