KDM5A KO lowered the exposure of ATRA to induce NB4 cell differentiation. (A) Proliferation assay of control (Ctrl) cells or KDM5A-KO cells treated with 0.5 nM ATRA or vehicle (dimethyl sulfoxide [DMSO]) and control cells treated with 10 nM ATRA for the indicated days. Viable cells were detected by using a trypan blue exclusion assay. The counts of the KO1 and KO2 cells with 0.5 nM ATRA were compared with the Ctrl cells with 10 nM ATRA. Statistical significance was determined by two-way analysis of variance. ****P < .0001. (B) CD11b⁺ or CD11c⁺ cells were detected by flow cytometry of control cells or KDM5A KO cells treated with indicated concentrations of ATRA for 4 days. ***P < .001, ###P < .001. (C) The morphology of control cells or KDM5A KO cells treated with 0.5 or 10 nM ATRA for 4 days. Bar = 15 μm. (D) The NBT test of control cells or KDM5A KO cells treated with indicated concentrations of ATRA or vehicle (DMSO) for 3 days. Values represent means ± standard deviation of the percentages of NBT-positive cells, n = 6.