Impaired response to BCR stimulation in Zfx-deficient B cells. (A) The analysis of BCR-induced Ca²⁺ mobilization in B cells from control and CD19-Cre⁺Zfx^flox/y CKO mice. Histogram profiles show intracellular Ca²⁺ flux of splenic B220⁺ B cells on the addition of anti-IgM. Data are representative of 3 independent experiments. (B) The analysis of proximal signaling events in BCR-stimulated B cells from control and CKO mice. Splenic B cells at the indicated time points after anti-IgM stimulation were analyzed for total tyrosine phosphorylation by Western blotting. Data are representative of 4 independent experiments. (C) The analysis of late signaling events in BCR-stimulated B cells from control and CKO mice. Splenic B cells at the indicated time points after anti-IgM stimulation were probed for cyclin D2 and Bcl-XL protein expression. Data are representative of 3 independent experiments. (D) The expression of Ccnd2 (cyclin D2) and Bcl2l1 (Bcl-XL) transcripts in BCR-stimulated B cells. Shown are normalized expression levels relative to the nonstimulated sample as determined by qPCR (mean ± SD of triplicate reactions).