AID-Induced Genotoxic Stress Promotes B Cell Differentiation in the Germinal Center via ATM and LKB1 Signaling

SummaryDuring an immune response, B cells undergo rapid proliferation and activation-induced cytidine deaminase (AID)-dependent remodeling of immunoglobulin (IG) genes within germinal centers (GCs) to generate memory B and plasma cells. Unfortunately, the genotoxic stress associated with the GC reaction also promotes most B cell malignancies. Here, we report that exogenous and intrinsic AID-induced DNA strand breaks activate ATM, which signals through an LKB1 intermediate to inactivate CRTC2, a transcriptional coactivator of CREB. Using genome-wide location analysis, we determined that CRTC2 inactivation unexpectedly represses a genetic program that controls GC B cell proliferation, self-renewal, and differentiation while opposing lymphomagenesis. Inhibition of this pathway results in increased GC B cell proliferation, reduced antibody secretion, and impaired terminal differentiation. Multiple distinct pathway disruptions were also identified in human GC B cell lymphoma patient samples. Combined, our data show that CRTC2 inactivation, via physiologic DNA damage response signaling, promotes B cell differentiation in response to genotoxic stress.

Graphical AbstractFigure optionsDownload high-quality image (273 K)Download as PowerPoint slideHighlights
► CREB coactivator CRTC2 is inactivated by DNA breaks via ATM and LKB1 signaling
► CRTC2 inactivation is from AID-induced DNA breaks in germinal center B cells
► CRTC2 regulates proliferation, plasma cell differentiation, and lymphomagenic genes
► Failed CRTC2 inactivation is from defective AID→ATM→LKB1→AMPK→CRTC2 pathway signaling