Pluripotent stem cells (PSCs) can self-renew or differentiate from naive or more differentiated, primed, pluripotent states established by specific culture conditions. Increased intracellular $$-ketoglutarate ($$KG) was shown to favor self-renewal in naive mouse embryonic stem cells (mESCs). The effect of $$KG or $$KG/succinate levels on differentiation from primed human PSCs (hPSCs) or mouse epiblast stem cells (EpiSCs) remains unknown. We examined primed hPSCs and EpiSCs and show that increased $$KG or $$KG-to-succinate ratios accelerate, and elevated succinate levels delay, primed PSC differentiation. $$KG has been shown to inhibit the mitochondrial ATP synthase and to regulate epigenome-modifying dioxygenase enzymes. Mitochondrial uncoupling did not impede $$KG-accelerated primed PSC differentiation. Instead, $$KG induced, and succinate impaired, global histone and DNA demethylation in primed PSCs. The data support $$KG promotion of self-renewal or differentiation depending on the pluripotent state.

Human embryonic stem cells can replicate indefinitely while maintaining their undifferentiated state and, therefore, are immortal in culture. This capacity may demand avoidance of any imbalance in protein homeostasis (proteostasis) that would otherwise compromise stem cell identity. Here we show that human pluripotent stem cells exhibit enhanced assembly of the TRiC/CCT complex, a chaperonin that facilitates the folding of 10% of the proteome. We find that ectopic expression of a single subunit (CCT8) is sufficient to increase TRiC/CCT assembly. Moreover, increased TRiC/CCT complex is required to avoid aggregation of mutant Huntingtin protein. We further show that increased expression of CCT8 in somatic tissues extends Caenorhabditis elegans lifespan in a TRiC/CCT-dependent manner. Ectopic expression of CCT8 also ameliorates the age-associated demise of proteostasis and corrects proteostatic deficiencies in worm models of Huntington's disease. Our results suggest proteostasis is a common principle that links organismal longevity with hESC immortality.

Background & Aims Hepatocytes differentiated from human embryonic stem cells (hESCs) have the potential to overcome the shortage of primary hepatocytes for clinical use and drug development. Many strategies for this process have been reported, but the functionality of the resulting cells is incomplete. We hypothesize that the functionality of hPSC-derived hepatocytes might be improved by making the differentiation method more similar to normal in vivo hepatic development. Methods We tested combinations of growth factors and small molecules targeting candidate signaling pathways culled from the literature to identify optimal conditions for differentiation of hESCs to hepatocytes, using qRT-PCR for stage-specific markers to identify the best conditions. Immunocytochemistry was then used to validate the selected conditions. Finally, induction of expression of metabolic enzymes in terminally differentiated cells was used to assess the functionality of the hESC-derived hepatocytes. Results Optimal differentiation of hESCs was attained using a 5-stage protocol. After initial induction of definitive endoderm (stage 1), we showed that inhibition of the WNT/??-catenin pathway during the 2nd and 3rd stages of differentiation was required to specify first posterior foregut, and then hepatic gut cells. In contrast, during the 4th stage of differentiation, we found that activation of the WNT/??-catenin pathway allowed generation of proliferative bipotent hepatoblasts, which then were efficiently differentiated into hepatocytes in the 5th stage by dual inhibition of TGF-?? and NOTCH signaling. Conclusion Here, we show that stage-specific regulation of the WNT/??-catenin pathway results in improved differentiation of hESCs to functional hepatocytes.

Pluripotent stem cells can become any cell type found in the body. Accordingly, one of the major challenges when working with pluripotent stem cells is producing a highly homogenous population of differentiated cells, which can then be used for downstream applications such as cell therapies or drug screening. The transcription factor Ascl1 plays a key role in neural development and previous work has shown that Ascl1 overexpression using viral vectors can reprogram fibroblasts directly into neurons. Here we report on how a recombinant version of the Ascl1 protein functionalized with intracellular protein delivery technology (Ascl1-IPTD) can be used to rapidly differentiate human induced pluripotent stem cells (hiPSCs) into neurons. We first evaluated a range of Ascl1-IPTD concentrations to determine the most effective amount for generating neurons from hiPSCs cultured in serum free media. Next, we looked at the frequency of Ascl1-IPTD supplementation in the media on differentiation and found that one time supplementation is sufficient enough to trigger the neural differentiation process. Ascl1-IPTD was efficiently taken up by the hiPSCs and enabled rapid differentiation into TUJ1-positive and NeuN-positive populations with neuronal morphology after 8 days. After 12 days of culture, hiPSC-derived neurons produced by Ascl1-IPTD treatment exhibited greater neurite length and higher numbers of branch points compared to neurons derived using a standard neural progenitor differentiation protocol. This work validates Ascl1-IPTD as a powerful tool for engineering neural tissue from pluripotent stem cells.

Genomic imprinting is an epigenetic phenomenon resulting in parent-of-origin-specific gene expression that is regulated by a differentially methylated region. Gene mutations or failures in the imprinting process lead to the development of imprinting disorders, such as Angelman syndrome. The symptoms of Angelman syndrome are caused by the absence of functional UBE3A protein in neurons of the brain. To create a human neuronal model for Angelman syndrome, we reprogrammed dermal fibroblasts of a patient carrying a defined three-base pair deletion in UBE3A into induced pluripotent stem cells (iPSCs). In these iPSCs, both parental alleles are present, distinguishable by the mutation, and express UBE3A. Detailed characterization of these iPSCs demonstrated their pluripotency and exceptional stability of the differentially methylated region regulating imprinted UBE3A expression. We observed strong induction of SNHG14 and silencing of paternal UBE3A expression only late during neuronal differentiation, in vitro. This new Angelman syndrome iPSC line allows to study imprinted gene regulation on both parental alleles and to dissect molecular pathways affected by the absence of UBE3A protein.