SIRT6 Controls Hematopoietic Stem Cell Homeostasis through Epigenetic Regulation of Wnt Signaling

Proper regulation of Wnt signaling is critical for the maintenance of hematopoietic stem cell (HSC) homeostasis. The epigenetic regulation of Wnt signaling in HSCs remains largely unknown. Here, we report that the histone deacetylase SIRT6 regulates HSC homeostasis through the transcriptional repression of Wnt target genes. Sirt6 deletion promoted HSC proliferation through aberrant activation of Wnt signaling. SIRT6-deficient HSCs exhibited impaired self-renewal ability in serial competitive transplantation assay. Mechanistically, SIRT6 inhibits the transcription of Wnt target genes by interacting with transcription factor LEF1 and deacetylating histone 3 at lysine 56. Pharmacological inhibition of the Wnt pathway rescued the aberrant proliferation and functional defect in SIRT6-deficient HSCs. Taken together, these findings disclose a new link between SIRT6 and Wnt signaling in the regulation of adult stem cell homeostasis and self-renewal capacity.