siRNA KD screen on dCLIP and TargetScan predicted miR-221/222-3p gene targets identifies Foxp1, Arid1a, and CD164 as regulators of CSR. (A) Frequency of viable versus frequency of surface IgG1⁺ for the siRNA KD of 70 gene targets predicted by dCLIP and TargetScan from a single screen on B cells pooled from four Δ mice stimulated and analyzed exactly as in the Fig. 1 miRNA screen. (B) Z-score plot for surface IgG1 for a rescreen of the top 10 and bottom 10 genes from A. (C) Gene expression data for Foxp1, Arid1a,and Cd164 from RNA-seq data. (D) Dual luciferase reporter assay results for Δ B cells transfected with either CM or miR-221/222-3p mimic and labeled psiCHECK-2 constructs containing >1 kb of each annotated 3′ UTR containing the miR-221/222 target sequence. Combined data from three to five independent experiments where each connected data point represents the average of four technical replicates normalized to CM luciferase mean within each experiment. *, P < 0.05; **, P < 0.01; ****, P < 0.0001.