Deciphering lymphoma-specific DNA methylation alterations in healthy B cells: a single-cell multiomics study

Recent studies have shown that clones harboring cancer driver mutations colonize our tissues as we age. It remains to be determined whether the same is true for epigenetic alterations, specifically DNA methylation (DNAm) changes. Due to the complexity of the DNA methylome, studying heterogeneous DNAm levels is challenging. To facilitate this research, we developed scTAM-seq, a single-cell targeted DNAm method that generates readouts from thousands of cells per run. Next, we investigated whether DNAm alterations observed in Mantle Cell Lymphoma (MCL) are also present in the normal B-cell compartment. We uncovered the Hub1-high B-cell population, characterized by the demethylation of 14 CpGs, so far considered MCL-specific events. This polyclonal B-cell population was detected in both the naive and more abundant memory B-cell stages. Hub1-high cells were found to be more frequent in the CD5+ B-cell compartment. Finally, we identified a minor subset of naive B cells expressing genes linked to the Hub1 CpGs, as well as genes associated with B1 and MCL cells.