Meis1 deletion leads to loss of LT-HSCs. Meis1-flox/CreER or control mice were treated with tamoxifen as described in the text. (A) Representative flow cytometry plots of CD48 and CD150 staining (gated on LSK fraction) showing significantly fewer LT-HSCs in the BMs of Meis1-deleted mice compared with controls. Bar graph depicts mean ± SEM of the percentage of LT-HSCs in lineage-depleted BM of control and Meis1-deleted mice (n = 7). (B) Bar graph representing colony numbers in methylcellulose medium. Data are shown as means ± SEM of total colony numbers/10 000 cells (n = 4). (C) Line graphs of blood counts (vertical axis) over time (horizontal axis) since tamoxifen treatment. Identities of the various groups are indicated in the legend on the right, with 5 mice in each group. Also shown is a representative gel image of PCR on tail blood 12 weeks after vehicle or tamoxifen treatment. (D) Transplantation experiment demonstrating that the loss of LT-HSCs with Meis1 deletion was cell autonomous. Flow plots are as in panel A, but depict donor LT-HSCs (recipients were lethally irradiated). The bar graph shows peripheral blood chimerism in recipients.