MicroRNA-directed pathway discovery elucidates an miR-221/222-mediated regulatory circuit in class switch recombination

MicroRNAs (miRNAs, miRs) regulate cell fate decisions by post-transcriptionally tuning networks of mRNA targets. We used miRNA-directed pathway discovery to reveal a regulatory circuit that influences Ig class switch recombination (CSR). We developed a system to deplete mature, activated B cells of miRNAs, and performed a rescue screen that identified the miR-221/222 family as a positive regulator of CSR. Endogenous miR-221/222 regulated B cell CSR to IgE and IgG1 in vitro, and miR-221/222-deficient mice exhibited defective IgE production in allergic airway challenge and polyclonal B cell activation models in vivo. We combined comparative Agog-HITS-CLIP and gene expression analyses to identify mRNAs bound and regulated by miR-221/222 in primary B cells. Interrogation of these putative direct targets uncovered functionally relevant downstream genes. Genetic depletion or pharmacological inhibition of Foxpl and Aridla confirmed their roles as key modulators of CSR to IgE and IgG1.

Automated summary

MicroRNAs regulate cell fate decisions by post-transcriptionally tuning networks of mRNA targets, with the miR-221/222 family identified as positive regulators of Ig class switch recombination. Endogenous miR-221/222 controls B cell CSR to IgE and IgG1, while Foxpl and Arid1a are confirmed as key modulators of CSR to IgE and IgG1 through genetic depletion or pharmacological inhibition.