Dual loss of ARID1A and ARID1B in hematopoietic compartment results in swift failure of hematopoietic development in mice. (A) BM cellularity in ARID1A and ARID1B double-deficient mice enumerated 2 to 4 days after third injection of poly(I:C). Cell counts represent number of leukocytes obtained from 2 femurs and 2 tibias for each mouse. (B) Percentages of HSC subsets, LT-HSCs, ST-HSCs, and MPP cells, in the BM of Arid1a^fl/fl;Arid1b^fl/fl;Mx1-Cre⁺ and control mice analyzed at 2 to 4 days after third injection of poly(I:C); n = 5 for control, and n = 5 for double-KO mice. (C-D) Frequencies of myeloid (C) and erythroid precursors (D) in flow cytometric evaluation of the BM of ARID1A and ARID1B double-deficient and WT mice assessed at 2 to 4 days after third injection of poly(I:C); proE, CD71⁺TER119^lo; EryA, CD71⁺TER119⁺FSC^hi; EryB, CD71⁺TER119⁺FSC^lo; and EryC, CD71⁻TER119⁺FSC^lo; n = 5 for control, and n = 5 for double-KO mice. (E) Percentages of mature (CD11b⁺Gr1^hi) and immature (CD11b⁺Gr1^med) granulocytes in the BM of WT and Arid1b KO mice; n = 5 for control, and n = 5 for double-KO mice. Control animals in these experiments comprised of either Arid1a^+/fl;Arid1b^fl/fl;Mx1-Cre⁻ or Arid1a^fl/fl;Arid1b^fl/fl;Mx1-Cre⁻ mice. Data are represented as mean ± SEM. Statistical difference between WT and KO mice was calculated using unpaired t test and is denoted as ∗P < .05.