Project description:Mouse embryonic stem cells (mESCs) are in naive pluripotency that represents the ground state of development, from which all cells in the mouse embryo are derived. In contrast, human embryonic stem cells (hESCs) are in a primed state of pluripotency with many different properties. Despite intense efforts to generate naive human pluripotent stem cells (hPSCs), it has not been possible to derive naive hPSCs without relying on transgene overexpression or chemicals. Here, we show that a transient treatment with Torin1, a selective inhibitor of mTOR, converted hPSCs from primed to naive pluripotency. The naive hPSCs were maintained in the same condition as mESCs in defined media with 2iLI (MEK inhibitor, GSK3b inhibitor, LIF and Insulin). Like mESCs, they exhibited high clonal efficiency, rapid cell proliferation, active mitochondrial respiration, X chromosome activation, DNA hypomethylation, and transcriptomes similar to those of human blastocysts than primed hESCs. Most importantly, the naive hPSCs significantly contributed to mouse embryos when transferred to mouse blastocysts. mTor inhibition induced nuclear translocation of TFE3, a critical transcription factor at the interplay of autophagy and pluripotency. TFE3 with mutated nuclear localization signal blocked the conversion from primed to naive pluripotency. It appears that by mimicking diapause at the cellular level, naive pluripotency in human can be readily attained from primed hPSCs, thus establishing the unified ground state of pluripotency in mammals.
Project description:Mouse embryonic stem cells (mESCs) are in naive pluripotency that represents the ground state of development, from which all cells in the mouse embryo are derived. In contrast, human embryonic stem cells (hESCs) are in a primed state of pluripotency with many different properties. Despite intense efforts to generate naive human pluripotent stem cells (hPSCs), it has not been possible to derive naive hPSCs without relying on transgene overexpression or chemicals. Here, we show that a transient treatment with Torin1, a selective inhibitor of mTOR, converted hPSCs from primed to naive pluripotency. The naive hPSCs were maintained in the same condition as mESCs in defined media with 2iLI (MEK inhibitor, GSK3b inhibitor, LIF and Insulin). Like mESCs, they exhibited high clonal efficiency, rapid cell proliferation, active mitochondrial respiration, X chromosome activation, DNA hypomethylation, and transcriptomes similar to those of human blastocysts than primed hESCs. Most importantly, the naive hPSCs significantly contributed to mouse embryos when transferred to mouse blastocysts. mTor inhibition induced nuclear translocation of TFE3, a critical transcription factor at the interplay of autophagy and pluripotency. TFE3 with mutated nuclear localization signal blocked the conversion from primed to naive pluripotency. It appears that by mimicking diapause at the cellular level, naive pluripotency in human can be readily attained from primed hPSCs, thus establishing the unified ground state of pluripotency in mammals.
Project description:The ability to support blastocyst chimera formation is the most critical property of naïve pluripotent stem cells (PSCs). Transient inhibition of mTOR converts human PSCs from primed to naive state. Naïve human PSCs cultured in 2iLI robustly incorporate into mouse embryonic development after injected to mouse blastocysts.
Project description:Gene expression profiling of immortalized human mesenchymal stem cells with hTERT/E6/E7 transfected MSCs. hTERT may change gene expression in MSCs. Goal was to determine the gene expressions of immortalized MSCs.
Project description:Transcriptional profiling of human mesenchymal stem cells comparing normoxic MSCs cells with hypoxic MSCs cells. Hypoxia may inhibit senescence of MSCs during expansion. Goal was to determine the effects of hypoxia on global MSCs gene expression.
Project description:Kynureninase is a member of a large family of catalytically diverse but structurally homologous pyridoxal 5'-phosphate (PLP) dependent enzymes known as the aspartate aminotransferase superfamily or alpha-family. The Homo sapiens and other eukaryotic constitutive kynureninases preferentially catalyze the hydrolytic cleavage of 3-hydroxy-l-kynurenine to produce 3-hydroxyanthranilate and l-alanine, while l-kynurenine is the substrate of many prokaryotic inducible kynureninases. The human enzyme was cloned with an N-terminal hexahistidine tag, expressed, and purified from a bacterial expression system using Ni metal ion affinity chromatography. Kinetic characterization of the recombinant enzyme reveals classic Michaelis-Menten behavior, with a Km of 28.3 +/- 1.9 microM and a specific activity of 1.75 micromol min-1 mg-1 for 3-hydroxy-dl-kynurenine. Crystals of recombinant kynureninase that diffracted to 2.0 A were obtained, and the atomic structure of the PLP-bound holoenzyme was determined by molecular replacement using the Pseudomonas fluorescens kynureninase structure (PDB entry 1qz9) as the phasing model. A structural superposition with the P. fluorescens kynureninase revealed that these two structures resemble the "open" and "closed" conformations of aspartate aminotransferase. The comparison illustrates the dynamic nature of these proteins' small domains and reveals a role for Arg-434 similar to its role in other AAT alpha-family members. Docking of 3-hydroxy-l-kynurenine into the human kynureninase active site suggests that Asn-333 and His-102 are involved in substrate binding and molecular discrimination between inducible and constitutive kynureninase substrates.