CRISPR/dCas9 DNA methylation editing is heritable during human haematopoiesis and can impair differentiation in vivo [Targeted BS-seq]

Ageing is associated with an abnormal increase of DNA methylation in human gene promoters, including in the bone marrow stem cells. DNA methylation patterns are further perturbed in haematological malignancies such as acute myeloid leukaemia (AML) but the physiological significance of such epigenetic changes is unknown. Using epigenetic editing of human stem/progenitor cells (HSPCs), we show evidence that p15 methylation affects haematopoiesis in vivo. We edited the CDKN2B (p15) promoter and ARF (p14) using dCas9-3A3L and observed DNA methylation spreading beyond the location of the gRNA. We find that despite a transient delivery system, DNA methylation is maintained during myeloid differentiation in vitro, and hypermethylation of the p15 promoter reduces gene expression. In vivo, edited human HSPCs can engraft the bone marrow of mice and targeted DNA methylation is maintained in HSPCs long term. Moreover, we identified how the epigenetic changes are conserved and inherited in both myeloid and lymphoid lineages. Although the proportion of myeloid (CD33+) and lymphoid (CD19+) cells is unaffected, monocyte (CD14+) populations decreased and granulocytes (CD66b+) increased in mice engrafted with p15 hypermethylated cells. We also observe significant changes in the proportions of multipotent and committed progenitor cells. This may have clinical relevance since we found that p15 promoter methylation is present in the peripheral blood of patients with clonal haematopoiesis. Our study shows DNA methylation can be targeted and maintained in human HSPCs and demonstrated functional relevance of aberrant DNA methylation on the p15 locus. As such, other ageing associated aberrant DNA methylation may impact haematopoiesis in vivo. Targeted bisulfite-sequencing data from the p15, p14 and p16 promoter after epigenetic editing or targeted-seq data at TET2 after genetic editing in haematopoetic stem and progenitor cells and in vitro experiments (colony forming unit assay) or in vivo engraftment into mice. Also targeted bisulfite sequencing of the p15 and p14 promoters in patients with Clonal Hematopoiesis