SIRT1 is a founding member of a sirtuin family of seven proteins and histone deacetylases. It is involved in cellular resistance to stress, metabolism, differentiation, aging, and tumor suppression. SIRT1-/- mice demonstrate embryonic and postnatal development defects. We examined hematopoietic and endothelial cell differentiation of SIRT1-/- mouse embryonic stem cells (ESCs) in vitro, and hematopoietic progenitors in SIRT1+/+, +/-, and -/- mice. SIRT1-/- ESCs formed fewer mature blast cell colonies. Replated SIRT1-/- BL-CFCs demonstrated defective hematopoietic potential. Endothelial cell...