Ectopic expression of NIK rescues the defect of Dyrk1a^BKO mice in peripheral B-cell development and survival. (A) Flow cytometric analyses of B220⁺ B cells and TCRβ⁺ T cells (A), immature (Imm; B220⁺CD93⁺) and mature (B220⁺CD93⁻) B cells as well as follicular (FO; B220⁺CD21^intCD23⁺) and marginal zone (MZ; B220⁺CD21^hiCD23⁻) B cells (B) in the spleen (SP), inguinal lymph nodes (iLN), and Peyer’s patches (PP) of wild-type, Dyrk1a^BKO, and Map3k14^BtgDyrk1a^BKO mice (6-8 weeks old). (C-D) Immunoblot analysis of the indicated proteins in the cytoplasmic (Cyt Ext) or nuclear (Nucl Ext) extracts of wild-type, Dyrk1a^BKO, and Map3k14^BtgDyrk1a^BKO splenic B cells stimulated with BAFF. Data are presented as a representative blot (C) and summary graphs of densitometrically quantified cytoplasmic p100 (ratio to β-Actin) and nuclear p52 (ratio to Lamin B) protein bands, presented as fold to 0 time point value (set to 1) (D). (E-F) Purified wild-type, Dyrk1a^BKO, and Map3k14^BtgDyrk1a^BKO splenic B cells were cultured for 48 h in 96-well plates (2 × 10⁵ cells per well) in the presence of medium control, BAFF, or CD40L and subjected to flow cytometry to quantify dead and viable cells. Data are presented as representative plots (E) and summary graphs (F). Data are representative of 3 independent experiments, and summary graphs were presented as mean ± SD with P values determined by an unpaired, 2-tailed Student t test (A-B,D,F). *P < .05; **P < .01; ***P < .001.