ARID1A Orchestrates SWI/SNF-mediated Sequential Binding of Transcription Factors and Its Deficiency Drives Pre-memory B-cell Fate and Lymphomagenesis [Arid1a_multiome]

ARID1A, a subunit of the canonical BAF nucleosome remodeling complex, is commonly mutated in lymphomas. Our study shows that ARID1A orchestrates B-cell fate during the germinal center (GC) response, facilitating cooperative and sequential binding of PU.1 and NF-kB at crucial genes for cytokine and CD40 signaling. The absence of ARID1A tilts GC cell-fate towards immature IgM+CD80-PDL2- memory B-cells, known for their potential to re-enter new GCs. When combined with BCL2 oncogene, ARID1A haploinsufficiency hastens the progression of aggressive follicular lymphomas in mice. Remarkably, follicular lymphoma patients with ARID1A-inactivating mutations preferentially display an immature memory B-cell-like state with increased transformation risk to aggressive disease. These observations offer mechanistic understanding into the emergence of both indolent and aggressive lymphomas in ARID1A-mutant patients through formation of immature memory-like clonal precursors. Lastly, we demonstrate that ARID1A mutation induces synthetic lethality to SMARCA2/4 inhibition, paving the way for potential precision therapy for high-risk patients. GC cells from splenocytes were sorted and underwent the manufacturer's nuclei preparation procedure. Then, about 20,000 nuclei were placed into a 10x Chromium X instrument. The remainder of the library preparation steps were conducted in accordance with the manufacturer's protocol