Post-Doctoral Fellow National Institutes of Health Bethesda, Maryland, United States
Abstract Text: IL-2 signaling is critical in maintaining immune homeostasis that requires precise regulation. To identify potential regulators of IL-2 signaling, we performed genome-wide CRISPR knockout screening in IL-2-dependent cells derived from a patient with Adult T-cell Leukemia (ATL). ATL cells are CD4+CD25+ with regulatory T cells (Treg)-like phenotype and constitutively active JAK-STAT signaling. Our CRISPR knockout screening showed enrichment of sgRNAs targeting PRDM1 that encodes Blimp-1 which inhibits IL-2 production in T cells; however, its role in IL-2 signaling remains unknown. Conditional knockout (CKO) of Prdm1 in mouse CD4+ T cells and Tregs resulted in increased expression of IL-2R subunits and pSTAT5 which was validated during an influenza infection where IL-2 signaling was enhanced in T follicular helper (TFH) and T follicular regulatory (TFR) cells in the absence of Blimp-1. Further, adoptive transfer of Prdm1 CKO Tregs into Rag2-/- mice resulted in augmented IL-2 signaling with attenuated ability to suppress inflammation in T-cell induced colitis. Consistently, CRISPR/Cas9-mediated deletion of PRDM1 in human CD4+ T cells and natural Tregs led to an enhanced IL-2 signaling. Blimp-1 ChIP-Seq in human Tregs demonstrated its direct binding to the key gene regulatory elements of IL-2 signaling. Finally, single-cell RNA-Seq analysis of ATL cells from acute patients showed a lower percentage of PRDM1+ populations leading to aberrant IL-2 signaling in these patients due to impaired regulation by Blimp-1. Thus, Blimp-1 is a pivotal regulatory node in IL-2 signaling that could be modulated for synchronizing T cell responses in human diseases such as ATL.
