Meis1 deletion leads to loss of HSC function. (A) Meis1-flox/CreER or control mice were treated with tamoxifen, as described in the text, and transplanted into lethally irradiated CD45.1 mice. (B) Representative flow cytometry plots on the left depict peripheral blood chimerism at 4 weeks after transplantation. Representative flow cytometry plots on the right depict the percentages of LSKs and LT-HSCs in the BM of transplantation recipients at 4 months. Shown are donor cells. (C) Recipient mice were killed at 4 months and whole BM was transplanted into lethally irradiated secondary recipient mice. Shown are representative flow cytometry plots depicting chimerism in the BM of secondary recipients. The recipients of Meis1-deleted BM died of hematopoietic failure.