A FLI1-KLF6 Axis Regulates Aging in Human Hematopoietic Stem and Progenitor Cells and Normalization of KLF6 Levels in Aged Cells Leads to Their Rejuvenation

Aging causes a gradual decline in hematopoietic stem cell (HSC) function, which increases the risk for hematological malignancies. While much has been done in murine models, human HSC aging impairment is less understood. We recently showed that Krüppel-like transcription factor 6 (KLF6) is among the top downregulated genes during human HSC aging, which correlates with H3K27ac loss at several upstream putative enhancers. Moreover, loss of KLF6 in human CD34 +cells resulted in impaired in vitro differentiation, increased colony-forming potential and a transcriptional profile similar to that of aged CD34 +CD38 -cells. We hypothesized that age-acquired deregulation of KLF6may be a key player in age-related HSC dysfunction and sought to fully characterize this. Thus, we isolated CD34 +cells from young (<32 y.o) and aged (>65 y.o.) healthy donors and performed CRISPR-Cas9 genome editing and transcriptional activation of KLF6, respectively, followed by epigenetic and transcriptional reprogramming, in vivo hematopoietic reconstitution, and analysis of DNA damage, apoptosis, and reactive oxygen species (ROS) levels.