SIRT1 deficiency compromises mouse embryonic stem cell hematopoietic differentiation, and embryonic and adult hematopoiesis in the mouse

Abstract

SIRT1 is a founding member of a sirtuin family of 7 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 ؊/؊ blast colony-forming cells demonstrated defective hematopoietic potential. Endothelial cell production was unaltered, but there were defects in formation of a primitive vascular network from SIRT1 ؊/؊ -derived embryoid bodies. Development of primitive and definitive progenitors derived from SIRT1 ؊/؊ ESCs were also delayed and/or defective. Differentiation delay/defects were associated with delayed capacity to switch off Oct4, Nanog and Fgf5 expression, decreased ␤-H1 globin, ␤-major globin, and Scl gene expression, and reduced activation of Erk1/2. Ectopic expression of SIRT1 rescued SIRT1 ؊/؊ ESC differentiation deficiencies. SIRT1 ؊/؊ yolk sacs manifested fewer primitive erythroid precursors. SIRT1 ؊/؊ and SIRT1 ؉/؊ adult marrow had decreased numbers and cycling of hematopoietic progenitors, effects more apparent at 5%, than at 20%, oxygen tension, and these progenitors survived less well in vitro under conditions of delayed growth factor addition. This suggests a role for SIRT1 in ESC differentiation and mouse hematopoiesis. (Blood. 2011;117(2):440-450) IntroductionMouse embryonic stem cells (ESCs) are pluripotent with capacity for unlimited self-renewal or differentiation into endoderm, ectoderm, and mesoderm. Self-renewal behavior in vitro is sustained with leukemia inhibitory factor (LIF). 1 With removal of LIF and in the absence of feeder layer cells, ESCs grow into spheres termed embryoid bodies (EBs), which generate hematopoietic and endothelial progeny recapitulating development of those populations in the yolk sac. 2 Hemangioblasts generate blast colonies in vitro displaying hematopoietic and endothelial potential. 3 The ESC/EB system provides a powerful in vitro model to explore cellular and molecular events that specify lineage choice and hematopoietic commitment.Sirtuins, or Sir2 family proteins, are conserved from bacteria to humans. 4 Sir2 modulates longevity and aging in yeast, Caenorhabditis elegans, and Drosophila. 5 Mammalian homologs of Sir2 encompass a family of 7 proteins (SIRT1-SIRT7), among which SIRT1 is the closest human homolog of the yeast Sir2 protein. 4 SIRT1 deacetylates proteins, including p53 and FOXO transcription factors, and plays many key functions including energy metabolism, differentiation, aging, and tumor suppression. [6][7][8][9][10] SIRT1 is expressed at high levels in mouse embryos with the highest SIR2␣ mRNA expression is embryonic day (E) 4.5 embryos. Although expression is down-regulated during subsequent embryogenesis, high level expression rema...

Upregulated sirtuin 1 by miRNA-34a is required for smooth muscle cell differentiation from pluripotent stem cells

“…SirT1 has been reported to be involved in a variety of cellular functions. 35 Recent data also suggests that SirT1 is a critical mediator in regulation of various development genes during stem cell differentiation 36 and has an important role in various cellular differentiations, including endothelial progenitor cells, 37 hematopoietic cells 38 and osteoblasts. 39 Traditionally, SirT1 has mainly been linked to gene repression; 40 however, accumulating evidence also strongly suggests that SirT1 can act both positively and negatively to control gene expression by recruiting a different set of coactivators and corepressors 41 or via a transcriptional mechanism.…”

Epigenetic regulation of aging stem cells

“…However, loss of Sirt1 confers a growth advantage in culture to HSCs under conditions of nutrient limitation (Narala et al, 2008), suggesting that SIRT1 negatively regulates HSC self-renewal under some conditions. In a different mouse model for Sirt1 constitutive deletion, SIRT1 promotes HSC self-renewal in low oxygen when assessed at early ages (Ou et al, 2010). Defects in HSC self-renewal under both basal and low oxygen conditions are exacerbated in older mice compared with young adults (Ou et al, 2010).…”

“…In a different mouse model for Sirt1 constitutive deletion, SIRT1 promotes HSC self-renewal in low oxygen when assessed at early ages (Ou et al, 2010). Defects in HSC self-renewal under both basal and low oxygen conditions are exacerbated in older mice compared with young adults (Ou et al, 2010). The role of SIRT1 in adult NSCs has not yet been characterized, but SIRT1 plays a role in directing cell fate decisions of embryonic neural progenitors in response to different extracellular conditions (Hisahara et al, 2008;Prozorovski et al, 2008).…”

SIRT1 is dispensable for function of hematopoietic stem cells in adult mice

“…Consistent with these concerns, a recent study showed that SIRT1 deficiency leads to impaired mouse embryonic stem cell (mESC) differentiation into hematopoietic progeny in vitro, indicating a possible role for SIRT1 in the development of primitive hematopoiesis in mouse embryos. 16 Several SIRT1 knockout models have been established using different targeting strategies in various genetic backgrounds, with the common feature of almost universal embryonic or perinatal mortality in the inbred 129SV background but a significant fraction of mice surviving to adulthood in other genetic backgrounds. [11][12][13][14] Specifically, the deletion of SIRT1 exon 4 in the C57BL/6 background allowed some of the mice to survive to weaning while conferring the same gross phenotype of SIRT1 deletion.…”