The ground state of pluripotency Wray, Jason; Kalkan, Tuzer; Smith, Austin G
Biochemical Society transactions,
08/2010, Letnik:
38, Številka:
4
Journal Article
Recenzirano
Pluripotency is defined as the capacity of individual cells to initiate all lineages of the mature organism in response to signals from the embryo or cell culture environment. A pluripotent cell has ...no predetermined programme; it is a blank slate. This is the foundation of mammalian development and of ES (embryonic stem) cell biology. What are the design principles of this naïve cell state? How is pluripotency acquired and maintained? Suppressing activation of ERKs (extracellular-signal-regulated kinases) is critical to establishing and sustaining ES cells. Inhibition of GSK3 (glycogen synthase kinase 3) reinforces this effect. We review the effect of selective kinase inhibitors on pluripotent cells and consider how these effects are mediated. We propose that ES cells represent a ground state, meaning a basal proliferative state that is free of epigenetic restriction and has minimal requirements for extrinsic stimuli. The stability of this state is reflected in the homogeneity of ES cell populations cultured in the presence of small-molecule inhibitors of MEK (mitogen-activated protein kinase/ERK kinase) and GSK3.
Transcription factor Stat3 directs self‐renewal of pluripotent mouse embryonic stem (ES) cells downstream of the cytokine leukemia inhibitory factor (LIF). Stat3 upregulates pivotal transcription ...factors in the ES cell gene regulatory network to sustain naïve identity. Stat3 also contributes to the rapid proliferation of ES cells. Here, we show that Stat3 increases the expression of mitochondrial‐encoded transcripts and enhances oxidative metabolism. Chromatin immunoprecipitation reveals that Stat3 binds to the mitochondrial genome, consistent with direct transcriptional regulation. An engineered form of Stat3 that localizes predominantly to mitochondria is sufficient to support enhanced proliferation of ES cells, but not to maintain their undifferentiated phenotype. Furthermore, during reprogramming from primed to naïve states of pluripotency, Stat3 similarly upregulates mitochondrial transcripts and facilitates metabolic resetting. These findings suggest that the potent stimulation of naïve pluripotency by LIF/Stat3 is attributable to parallel and synergistic induction of both mitochondrial respiration and nuclear transcription factors.
Synopsis
The LIF/STAT3 pathway promotes naïve pluripotency and proliferation in embryonic stem cells. To do this, in addition to its nuclear role, STAT3 translocates to the mitochondrion, regulates mitochondrial transcription and enhances mitochondrial respiration.
The LIF/Stat3 axis promotes mitochondrial gene expression and respiration in ES cells.
Mitochondrial respiration determines optimal ES cell proliferation.
LIF‐dependent up‐regulation of mitochondrial activity contributes to induction of naïve pluripotency.
The LIF/STAT3 pathway promotes naïve pluripotency and proliferation in embryonic stem cells. To do this, in addition to its nuclear role, STAT3 translocates to the mitochondrion, regulates mitochondrial transcription and enhances mitochondrial respiration.
In recent years, there has been a growing interest in therapeutic peptides within the pharmaceutical industry with more than 50 peptide drugs on the market, approximately 170 in clinical trials, and ...>200 in preclinical development. However, the current state of the art in peptide synthesis involves primarily legacy technologies with use of large amounts of highly hazardous reagents and solvents and little focus on green chemistry and engineering. In 2016, the ACS Green Chemistry Institute Pharmaceutical Roundtable identified development of greener processes for peptide API as a critical unmet need, and as a result, a new Roundtable team formed to address this important area. The initial focus of this new team is to highlight best practices in peptide synthesis and encourage much needed innovations. In this Perspective, we aim to summarize the current challenges of peptide synthesis and purification in terms of sustainability, highlight possible solutions, and encourage synergies between academia, the pharmaceutical industry, and contract research organizations/contract manufacturing organizations.
The genomes of cancers deficient in mismatch repair contain exceptionally high numbers of somatic mutations. In a proof-of-concept study, we previously showed that colorectal cancers with mismatch ...repair deficiency were sensitive to immune checkpoint blockade with antibodies to programmed death receptor–1 (PD-1). We have now expanded this study to evaluate the efficacy of PD-1 blockade in patients with advanced mismatch repair–deficient cancers across 12 different tumor types. Objective radiographic responses were observed in 53% of patients, and complete responses were achieved in 21% of patients. Responses were durable, with median progression-free survival and overall survival still not reached. Functional analysis in a responding patient demonstrated rapid in vivo expansion of neoantigen-specific T cell clones that were reactive to mutant neopeptides found in the tumor. These data support the hypothesis that the large proportion of mutant neoantigens in mismatch repair–deficient cancers make them sensitive to immune checkpoint blockade, regardless of the cancers’ tissue of origin.
The distinction between acquired aplastic anemia (AA) and hypocellular myelodysplastic syndrome (hMDS) is often difficult, especially nonsevere AA. We postulated that somatic mutations are present in ...a subset of AA, and predict malignant transformation. From our database, we identified 150 AA patients with no morphological evidence of MDS, who had stored bone marrow (BM) and constitutional DNA. We excluded Fanconi anemia, mutations of telomere maintenance, and a family history of BM failure (BMF) or cancer. The initial cohort of 57 patients was screened for 835 known genes associated with BMF and myeloid cancer; a second cohort of 93 patients was screened for mutations in ASXL1, DNMT3A, BCOR, TET2, and MPL. Somatic mutations were detected in 19% of AA, and included ASXL1 (n = 12), DNMT3A (n = 8) and BCOR (n = 6). Patients with somatic mutations had a longer disease duration (37 vs 8 months, P < .04), and shorter telomere lengths (median length, 0.9 vs 1.1, P < .001), compared with patients without mutations. Somatic mutations in AA patients with a disease duration of >6 months were associated with a 40% risk of transformation to MDS (P < .0002). Nearly one-fifth of AA patients harbor mutations in genes typically seen in myeloid malignancies that predicted for later transformation to MDS.
•Acquired mutations of myeloid-related genes are present in a proportion of AA patients.•Somatic mutations in AA predict higher risk of transformation to MDS.
Mouse embryonic stem cells are continuous cell lines derived directly from
the fetal founder tissue of the preimplantation embryo. They can be expanded in
culture while retaining the functional ...attributes of pluripotent early embryo
cells. In particular, they can participate fully in fetal development when
reintroduced into the embryo. The capacity for multilineage differentiation is
reproduced in culture where embryonic stem cells can produce a wide range of
well-defined cell types. This has stimulated interest in the isolation of
analogous cells of human origin. Such human pluripotent stem cells could
constitute a renewable source of more differentiated cells that could be
employed to replace diseased or damaged tissue by cellular transplantation. In
this review, the relationships between mouse embryonic stem cells, resident
pluripotent cells in the embryo, and human embryo-derived cell lines are
evaluated, and the prospects and challenges of embryo stem cell research are
considered.
An enantioselective preparation of 2,5-cis-disubstituted pyrrolidines has been achieved via a dynamic kinetic asymmetric transformation (DyKAT) of racemic donor−acceptor cyclopropanes and ...(E)-aldimines. Mechanistic studies suggest that isomerization of the aldimine or resultant iminium to the Z geometry is not a pathway that furnishes the observed 2,5-cis-disubstituted products.
Human immunodeficiency virus-1 (HIV-1) infection disrupts the intestinal immune system, leading to microbial translocation and systemic immune activation. We investigated the impact of HIV-1 ...infection on the intestinal microbiome and its association with mucosal T-cell and dendritic cell (DC) frequency and activation, as well as with levels of systemic T-cell activation, inflammation, and microbial translocation. Bacterial 16S ribosomal DNA sequencing was performed on colon biopsies and fecal samples from subjects with chronic, untreated HIV-1 infection and uninfected control subjects. Colon biopsies of HIV-1-infected subjects had increased abundances of Proteobacteria and decreased abundances of Firmicutes compared with uninfected donors. Furthermore at the genus level, a significant increase in Prevotella and decrease in Bacteroides was observed in HIV-1-infected subjects, indicating a disruption in the Bacteroidetes bacterial community structure. This HIV-1-associated increase in Prevotella abundance was associated with increased numbers of activated colonic T cells and myeloid DCs. Principal coordinates analysis demonstrated an HIV-1-related change in the microbiome that was associated with increased mucosal cellular immune activation, microbial translocation, and blood T-cell activation. These observations suggest that an important relationship exists between altered mucosal bacterial communities and intestinal inflammation during chronic HIV-1 infection.
Mesenchymal stem cells (MSCs) are defined as cells that undergo sustained in vitro growth and are able to give rise to multiple mesenchymal lineages. Although MSCs are already used in regenerative ...medicine little is known about their in vivo behavior and developmental derivation. Here, we show that the earliest wave of MSC in the embryonic trunk is generated from Sox1
+ neuroepithelium but not from mesoderm. Using lineage marking by direct gfp knock-in and Cre-recombinase mediated lineage tracing, we provide evidence that Sox1
+ neuroepithelium gives rise to MSCs in part through a neural crest intermediate stage. This pathway can be distinguished from the pathway through which Sox1
+ cells give rise to oligodendrocytes by expression of PDGFRβ and A2B5. MSC recruitment from this pathway, however, is transient and is replaced by MSCs from unknown sources. We conclude that MSC can be defined as a definite in vivo entity recruited from multiple developmental origins.
A highly asymmetric vinylogous addition of acyclic silyl enol ethers to siloxyvinyldiazoacetate is described. The reaction features a diastereoselective 1,4-siloxy group migration event. Products are ...obtained in up to 97% ee. When more sterically crowded silyl enol ethers are employed, an enantioselective formal 3+2 cycloaddition becomes the dominant reaction pathway. Control experiments reveal the (Z)-olefin geometry to be critical for high levels of enantiocontrol.
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