Derivation of human parthenogenetic stem cell lines.

Pluripotent stem cells (PSCs) derived from parthenogenetically activated human oocytes demonstrate the typical characteristics displayed by human embryonic stem cells (hESCs) including infinite division and in vitro and in vivo differentiation into cells of all germ lineages. Different activation techniques allow the creation of either human leukocyte antigen (HLA) heterozygous human parthenogenetic stem cell (hpSC) lines, which are HLA-matched/histocompatible with the oocyte donor, or HLA-homozygous hpSC lines, which may be histocompatible to significant segments of the human population. This immune-matching advantage, combined with the advantage of derivation from nonviable human embryos that originate from unfertilized parthenogenetically activated oocytes, makes hpSCs a promising source of PSCs for cell-based transplantation therapy.

Derivation of high-purity definitive endoderm from human parthenogenetic stem cells using an in vitro analog of the primitive streak.

Human parthenogenetic stem cells (hpSCs) are pluripotent stem cells with enormous potential as cell sources for cell-based therapies: hpSCs may have histocompatibilty advantages over human embryonic stem cells (hESCs) and derivation of hpSCs does not require viable blastocyst destruction. For translation of all pluripotent stem cell-based therapies, derivation of differentiated cell products that are not contaminated with undifferentiated cells is a major technical roadblock. We report here a novel method to derive high-purity definitive endoderm (DE) from hpSCs, based on reproducing features of the normal human embryonic microenvironment.

Human parthenogenetic stem cells produce enriched populations of definitive endoderm cells after trichostatin A pretreatment.

Human parthenogenetic stem cells (hpSC) hold great promise as a source of pluripotent stem cells for cell-based transplantation therapy due to their ethical method of derivation as well as the enhanced capacity for immunomatching with significant segments of the human population. We report here the directed differentiation of hpSC to produce enriched populations of definitive endoderm. Moreover, we find that treatment of undifferentiated hpSC by trichostatin A (TSA) before applying the directed differentiation protocol significantly increases the proportion of definitive endoderm cells in the final population.

Equivalence of conventionally-derived and parthenote-derived human embryonic stem cells.

Background: As human embryonic stem cell (hESC) lines can be derived via multiple means, it is important to determine particular characteristics of individual lines that may dictate the applications to which they are best suited. The objective of this work was to determine points of equivalence and differences between conventionally-derived hESC and parthenote-derived hESC lines (phESC) in the undifferentiated state and during neural differentiation.

Methodology/principal Findings: hESC and phESC were exposed to the same expansion conditions and subsequent neural and retinal pigmented epithelium (RPE) differentiation protocols.

Repression of sestrin family genes contributes to oncogenic Ras-induced reactive oxygen species up-regulation and genetic instability.

Oncogenic mutations within RAS genes and inactivation of p53 are the most common events in cancer. Earlier, we reported that activated Ras contributes to chromosome instability, especially in p53-deficient cells. Here we show that an increase in intracellular reactive oxygen species (ROS) and oxidative DNA damage represents a major mechanism of Ras-induced mutagenesis.

The antioxidant function of the p53 tumor suppressor.

It is widely accepted that the p53 tumor suppressor restricts abnormal cells by induction of growth arrest or by triggering apoptosis. Here we show that, in addition, p53 protects the genome from oxidation by reactive oxygen species (ROS), a major cause of DNA damage and genetic instability. In the absence of severe stresses, relatively low levels of p53 are sufficient for upregulation of several genes with antioxidant products, which is associated with a decrease in intracellular ROS.

Activation of Ras-Ral pathway attenuates p53-independent DNA damage G2 checkpoint.

Earlier we have found that in p53-deficient cells the expression of activated Ras attenuates the DNA damage-induced arrest in G(1) and G(2). In the present work we studied Ras-mediated effects on the G(2) checkpoint in two human cell lines, MDAH041 immortalized fibroblasts and Saos-2 osteosarcoma cells. The transduction of the H-Ras mutants that retain certain functions (V12S35, V12G37, and V12C40 retain the ability to activate Raf or RalGDS or phosphatidylinositol 3-kinase, respectively) as well as the activated or dominant-negative mutants of RalA (V23 and N28, respectively) has revealed that the activation of Ras-RalGEFs-Ral pathway was responsible for the attenuation of the G(2) arrest induced by ethyl metanesulfonate or doxorubicin.