Age-Like Methylation Changes of HSCs in GADD45B Knockout Mice Define Methylation Sites Associated With Loss of Function

Hematopoietic stem cells (HSCs) self-renew and differentiate into all blood cells maintaining the hematopoietic system. Age-related HSC dysfunction impacts all of hematopoiesis, with DNA methylation alterations in aged HSCs contributing to altered function. Growth Arrest and DNA Damage-inducible proteins (Gadd45a, Gadd45b, and Gadd45g) are expressed in HSC activation, and Gadd45b has been reported to induce DNA demethylation. Thus, we explored the relationship between Gadd45b, DNA methylation and age-related HSC changes. WGBS on HSCs from GADD45B knockout mice demonstrated young knockout HSCs have increased DNA methylation, with both unique and overlapping methylation changes compared to aged wild-type HSCs without reflecting aging transcriptional changes. Peripheral blood and bone marrow analysis, competitive transplants, and single-cell culture analyses showed no significant loss of functional potential in the aberrantly methylated GADD45B knockout HSCs. We concluded these altered methylation sites don't alter HSC potential. We generated a searchable HSC DNA methylation database incorporating available datasets and present a truncated list of methylation sites associated with changes in HSC function for prioritization to target for resetting the age-associated loss of HSC potential.