The Reg1/Reg3-Nfkbiz axis controls lymphoid-myeloid fate decision. (A-C) Representative flow cytometry plots (A), frequencies (B) and cell numbers (C) of HSPC subpopulations in mice of the indicated genotypes at day 14 after tamoxifen treatment. Ctrl, CreERT2⁺Reg1^fl/+Reg3^+/+Nfkbiz^fl/+; Nfkbiz^CreERT2, CreERT2⁺Reg1^fl/+Reg3^+/+Nfkbiz^fl/fl; DKO^CreERT2, CreERT2⁺Reg1^fl/flReg3^–/–Nfkbiz^+/+; TKO^CreERT2, CreERT2⁺Reg1^fl/flReg3^–/–Nfkbiz^fl/fl (n = 4 each). Asterisks represents P value (∗P < .05; ∗∗P < .01; ∗∗∗∗P < .0001). (D-F) Representative flow cytometry plots (D), and frequency (E) and cell number (F) of B cells in the indicated mice (n = 4 each). (G-I) Representative flow cytometry plots (G) and frequencies (H) and cell numbers (I) of myeloid cells in the indicated mice (n = 4 each). (J-L) In vitro B-cell differentiation using Lin^–Kit⁺IL-7Rα⁺ FL cells derived from the indicated genotypes. Progenitor cells were differentiated under B-cell–promoting condition in the presence of 4-OHT. Ctrl, CreERT2⁺Reg1^fl/+Reg3^+/+Nfkbiz^fl/+; Nfkbiz^CreERT2, CreERT2⁺Reg1^fl/+Reg3^+/+Nfkbiz^fl/fl; DKO^CreERT2, CreERT2⁺Reg1^fl/flReg3^–/–Nfkbiz^+/+; TKO^CreERT2, CreERT2⁺Reg1^fl/flReg3^–/–Nfkbiz^fl/fl. Representative flow cytometry plots (J), frequency (K), and absolute number (L) of CD19⁺B220⁺ cells are shown. n = 6. Data are a composite of 2 independent experiments (A-I) or a representative of 2 independent experiments (J-L). Data are presented as mean ± SD (C,E-F,H-I,K-L). Statistical significance was calculated by 1-way ANOVA with Holm-Sidak multiple comparisons test. 4-OHT, 4-hydroxytamoxifen.