MYB deletion affects KSL cell number and differentiation.

<p>(A) Flow cytometric analysis of bone marrow from <i>Myb</i>^<i>F/F</i>:<i>MxCre</i> mutant mice and <i>Myb</i>^<i>+/+</i>:<i>MxCre</i> control animals, 24 or 48 hours following in vivo induction of the <i>Myb</i>^<i>F/F</i> allele deletion by p(I:C) injection. The representative two-dimensional plots show the gating on lineage negative cells and the typical KIT⁺/SCA-1⁺/LIN^- (KSL) staining. Histograms represent the percentage of KSL cells within the total bone marrow population, with numbers presented as mean ± SEM, determined from 3 independent experiments (***, p<0.0001). (B) Control and <i>Myb</i>-deleted KSL were sorted and seeded in methylcellulose. Colony numbers and size were assessed after 6 days. The right histograms represent total colony numbers and the relative proportions of colonies based on size respectively. Pictures of the counted colonies are presented in the left panels. (C) Sorted KSL from control and <i>Myb</i>-deleted animals 24 hours post injection of poly(I:C) were cultured into liquid medium containing SCF, FL and TPO. After culturing for 2 days, the cells were re-stained and analysed by flow cytometry for expression of CD11 and CD41 (left panel). Cells from the <i>Myb</i>^<i>F/F</i>:<i>MxCre</i> bone marrow were sorted on the basis of CD11 and CD41. The sorted cells were spun onto glass slides and stained with Diff-Quick (upper right panel). The images show representative cells demonstrating monocytic (CD11b⁺) and megakaryocytic (CD11b⁺CD41⁺ and CD11b^-CD41⁺) morphologies.