It has been further documented in the DNMT3A knockout (KO) CLL-mice model that DNMT3A gene expression controls global DNA methylation patterns in haematopoietic stem cells, and in addition, DNMT3A was shown to be critical for B cell and CD8+ T cell development [18, 40, 45]. This evidence concerns the gene CD8A and B-cell chronic lymphocytic leukemia.