NFATc1 transcription factor regulates human B-cell development in early life 4341

Abstract Description In early life, humans produce B cells that are developmentally and functionally distinct from their adult counterparts. Yet, the molecular mechanisms that regulate these differences are unknown. The NFAT (Nuclear Factor of Activated T cell) family of transcription factors regulates immune cell survival, proliferation, and effector functions implicated in cancers, including leukemia. In mice, one of the five members of NFAT family, NFATc1, is critical for developing early-life B cells (B-1) but dispensable for adult B cells (B-2). To determine if humans also require NFATc1 for B-cell development, we mapped human B-lymphopoiesis across the lifespan using multi-omics single-cell sequencing. We quantified NFATc1 expression across human gestation (n = 10 fetal liver) and throughout adulthood (n = 10 bone marrow). NFATc1 is first expressed during the pre-pro-B stage of B-cell commitment. In silico analysis revealed that, like mice, NFATc1 regulates B-cell development in early life but not in adulthood. We validated these findings using CRISPR-Cas9 to knockout NFATc1 on human primary CD34+ progenitors from fetal and adult donors. While NFATc1+/+ fetal progenitors survive >3 weeks in cell culture and differentiate into mature IgM+/IgD+ B cells, their NFATc1-/- counterpart undergo cell death within 2 weeks. Thus, we propose that NFATc1 may function as a master regulator of early-life-B-lymphopoiesis and play a role in human B-cell-mediated diseases in childhood, including leukemias. Funding Sources Supported by Sao Paulo Resarch Foundation (2023/16705-5); Bill and Melinda Gates Foundation; Lowance Center for Human Immunology, NIAID (R21AI180928) and Emory University. Topic Categories Hematopoiesis and Immune System Development (HEM)