Epigenetic Signatures Associated with Different Levels of Differentiation Potential in Human Stem Cells

Background

The therapeutic use of multipotent stem cells depends on their differentiation potential, which has been shown to be variable for different populations. These differences are likely to be the result of key changes in their epigenetic profiles.

Methodology/Principal Findings

to address this issue, we have investigated the levels of epigenetic regulation in well characterized populations of pluripotent embryonic stem cells (ESC) and multipotent adult stem cells (ASC) at the trancriptome, methylome, histone modification and microRNA levels. Differences in gene expression profiles allowed classification of stem cells into three separate populations including ESC, multipotent adult progenitor cells (MAPC) and mesenchymal stromal cells (MSC). The analysis of the PcG repressive marks, histone modifications and gene promoter methylation of differentiation and pluripotency genes demonstrated that stem cell populations with a wider differentiation potential (ESC and MAPC) showed stronger representation of epigenetic repressive marks in differentiation genes and that this epigenetic signature was progressively lost with restriction of stem cell potential. Our analysis of microRNA established specific microRNA signatures suggesting specific microRNAs involved in regulation of pluripotent and differentiation genes.

Conclusions/Significance

Our study leads us to propose a model where the level of epigenetic regulation, as a combination of DNA methylation and histone modification marks, at differentiation genes defines degrees of differentiation potential from progenitor and multipotent stem cells to pluripotent stem cells.     

Role of oxidative stress, mitochondrial membrane potential, and calcium homeostasis in nickel sulfate-induced human lymphocyte death in vitro

When isolated human lymphocytes were treated in vitro with various concentrations of nickel sulfate (NiSO4) (0-4 mM) at 37 degrees C for 4 h, both concentration- and time-dependent effects of NiSO4 on lymphocyte death were observed. Increased generation of hydrogen peroxide, depletion of both nonprotein and protein sulfhydryl contents, and lipid peroxidation were induced by NiSO4. NiSO4-induced lymphocyte death was significantly prevented by pre-treatment with either catalase, or dimethylthiourea/mannitol, or deferoxamine, or excess glutathione/N-acetylcysteine. Cotreatment with cyclosporin A (a specific inhibitor of mitochondrial membrane potential) not only inhibited NiSO4-induced mitochondrial membrane potential, but also significantly prevented Ni compound-induced lymphocyte death. NiSO4-induced lymphocyte death was also significantly prevented by modulating intracellular calcium fluxes using both Ca2+ channel blockers and intracellular Ca2+ antagonist. Thus, the mechanism of NiSO4-induced activation of lymphocyte death signalling pathways involves not only the excess generation of different types of oxidative stress but also NiSO4-induced loss of mitochondrial membrane potential and destabilization of cellular calcium homeostasis as well.     

Effect of mutants and inhibitors on mitochondrial transport systems in vivo in yeast

We have reported elsewhere (Wills, C. and Martin, T. (1984) Biochim. Biophys. Acta 782, 274-284) that one or more mitochondrial transport systems may be involved in the regulation of the inducible alcohol dehydrogenase of yeast, ADH-II. In order to investigate this phenomenon further, it was necessary to determine which of these systems operate in the cell in vivo. We give in this paper preliminary evidence that inhibitors of the malate-phosphate (n-butyl malonate), malate-citrate (hydroxycitrate) and malate-alpha-ketoglutarate (aminooxyacetate or cycloserine) transport systems all operate in vivo. While the demonstration of the in vivo inhibitory activity of n-butyl malonate and hydroxycitrate is entirely by physiological methods, that of the transaminase inhibitors aminooxyacetate and cycloserine depends in part on the isolation of mutants capable of growth on glycerol in minimal medium. On this medium these mutants depend on the malate-aspartate shuttle for growth, and as expected the transaminase inhibitors prevent their growth. Two of the mutants show an enhanced rate of mitochondrial glutamate uptake. A preliminary survey of the properties of the glycerol growth mutants is presented, showing that the probable mode of action of these mutants is an increase in the efficiency of the malate-aspartate shuttle.     

Acute stimulation by lutropin of mitochondrial protein synthesis in small luteal cells

A two-dimensional electrophoretic technique was used to study the effect of acute stimulation of bovine luteal cells with lutropin on protein synthesis. Cells were incubated for 30 min with [35S]methionine in the presence of stimulating levels of luteinizing hormone (lutropin), after which the proteins were analyzed by autoradiography. Lutropin or N6,2'-O-dibutyryl-adenosine 3',5'-phosphate (Bt2cAMP) induced the labelling of three proteins, referred to as proteins A, B and C. Protein A, had a molecular mass of 28 kDa and an isoelectric point (pI) of 6.7. Proteins B and C had a molecular mass of 27 kDa and pI of 6.2 and 6.4 respectively. After subcellular fractionation, the three proteins were found to be markedly concentrated in the only fraction enriched in an established mitochondrial marker. Moreover, protein A was one of the major mitochondrial newly synthesized proteins. Its appearance was observed after a 5-min incubation and was prevented by 100 microM cycloheximide. The acute accumulation of proteins A, B and C in mitochondria, the site of the rate-limiting step of steroidogenesis, suggest that they could be involved in the mechanism of stimulation by lutropin of progesterone synthesis.     

Evaluation of Cassava Cultivars for Resistance to Cassava Mosaic Disease and Yield Potential in Central African Republic

Eleven cassava genotypes were tested against cassava mosaic disease (CMD) and compared to a local susceptible cultivar in field conditions from June 2011 to July 2012 in Central African Republic (CAR) at two sites representative of the savanna (Damara) and forest (Pissa) zones of the country. The mean number of whiteflies observed on plants varied among genotypes within each site, but was found nearly three times higher at Damara than at Pissa, resulting in a CMD incidence nearly five times higher at Damara than at Pissa. However, no relation was observed between the number of insect on the plants and the level of susceptibility/resistance of the genotypes. The difference of disease pressure between the two sites revealed high level of resistance in several genotypes, while some other ones indicated rather only a partial resistance. Nevertheless, none of the genotypes tested was found immune, in the end, the virus being detected at least in one site in every genotype, including those ones presenting no symptoms in both sites. The impact of CMD on yield components was assessed on the local susceptible check and three partially resistant genotypes, showing that the disease has no significant effect on the tuberous roots number as well as their weight in both sites. The yield potential varied among different genotypes and between the two sites, the mean number of tuberous roots as well as their mean weight being higher in Damara than in Pissa. This study identified highly resistant genotypes such as ‘Gabon’ that performed well in both sites, and ‘91/02322’ that was symptomless and presented a yield potential equivalent to the local check. These genotypes could be distributed to growers with the main advantage to be resistant to CMD and, therefore, reducing the risk to spread sources of inoculum all over the cassava cropping areas in the country.     

Phylogenetic relationships between Hapalemur species and subspecies based on mitochondrial DNA sequences

Background  

Phylogenetic relationships of the genus Hapalemur remains controversial, particularly within the Hapalemur griseus species group. In order to obtain more information on the taxonomic status within this genus, and particularly in the cytogenetic distinct subspecies group of Hapalemur griseus, 357 bp sequence of cytochrome b and 438 bp of 12S mitochondrial DNAs were analyzed on a sample of animals captured in areas extending from the north to the south-east of Madagascar. This sample covers all cytogenetically defined types recognized of the genus Hapalemur.     

Induction of Potent Neutralizing Antibody Responses by a Designed Protein Nanoparticle Vaccine for Respiratory Syncytial Virus

1. Download high-res image (168KB)
2. Download full-size image