Asxl1^tm1Bc/tm1Bc mutant mice exhibit reduced B-cell lymphopoiesis. (A) Flow cytometric profiles of adult (> 15 weeks old) peripheral blood (PB), spleen, and bone marrow (BM) show a relative decrease in B220- and IgM/IgD-positive cells in Asxl1^tm1Bc/tm1Bc (mut) tissues compared with wild type (wt). (B) Absolute bone marrow cell numbers in adult femur expressing the markers B220; B220 and CD43; B220 and IgM; and IgM and IgD are significantly lower in Asxl1^tm1Bc/tm1Bc mice compared with wild type (n = 8 each genotype except n = 4 for B220 and IgM). (C) Absolute cell numbers from > 15-week-old spleen expressing the markers B220, and IgM and IgD, are lower in Asxl1^tm1Bc/tm1Bc mice compared with wild type (n = 8 each genotype). (D) In vitro colony formation of committed pre-B-lymphocyte progenitors (CFU–IL-7 assay) from adult bone marrow (> 15 weeks old) is significantly reduced in cultures of Asxl1^tm1Bc/tm1Bc group B compared with wild type (n = 7 wt, 8 mutant). *P < .05.