Menin and Mll1 function independently during hematopoietic regeneration. (A-B) Donor-derived (CD45.1) cells in the peripheral blood of recipients 25 weeks posttransplantation. PBL*, myeloid-gated peripheral blood leukocytes used to assess donor contribution independent of the B-cell deficit in Men1-deficient BM (see “Methods”). BM cells of the indicated genotypes were generated by pI:pC injection, harvested 13 days after the first injection, and then mixed with wild-type CD45.2 BM cells and injected into lethally irradiated recipients. Control donor BM was from pI:pC-injected littermates not harboring the Mx1-cre transgene. (C-D) Donor contribution in the lin⁻/c-Kit⁺ fraction of BM from the same recipients as in panels A-B. To facilitate pairwise comparisons, data from the Men1^Δ/Δ group in A are regraphed in B; n = 9-11 animals per genotype. Statistical significance was determined using the unpaired Student t test; *P ≤ .05; **P ≤ .01. (A) P = .0098. (B) P = .0027. (C) P = .041. (D) P = .0284.