Plasma cells from bone marrow were isolated using the Miltenyi CD138 Multiple Myeloma MACS kit, following the manufacturer's standard protocol. ATAC-seq was performed in accordance with the Buenrostro protocol (Curr Protoc Mol Biol. 2015). Starting with 50.000 CD138+ plasma cells, library construction was performed using the hyperactive transposase Tn5. NGS adapters were pre-loaded onto the transposase, allowing simultaneous chromatin fragmentation and adapter integration into open chromatin regions.