LSD1 regulates the balance between self-renewal and differentiation in human embryonic stem cells

We identify LSD1 (lysine-specific demethylase 1; also known as KDM1A and AOF2) as a key histone modifier that participates in the maintenance of pluripotency through the regulation of bivalent domains, a chromatin environment present at the regulatory regions of developmental genes that contains both H3K4 di/trimethylation and H3K27 trimethylation marks. LSD1 occupies the promoters of a subset of developmental genes that contain bivalent domains and are co-occupied by OCT4 and NANOG in human embryonic stem cells, where it controls the levels of H3K4 methylation through its demethylase activity. Thus, LSD1 has a role in maintaining the silencing of several developmental genes in human embryonic stem cells by regulating the critical balance between H3K4 and H3K27 methylation at their regulatory regions.     

Dedifferentiation, transdifferentiation and reprogramming: three routes to regeneration

The ultimate goal of regenerative medicine is to replace lost or damaged cells. This can potentially be accomplished using the processes of dedifferentiation, transdifferentiation or reprogramming. Recent advances have shown that the addition of a group of genes can not only restore pluripotency in a fully differentiated cell state (reprogramming) but can also induce the cell to proliferate (dedifferentiation) or even switch to another cell type (transdifferentiation). Current research aims to understand how these processes work and to eventually harness them for use in regenerative medicine.     

Adenovirus-5-vectored P. falciparum vaccine expressing CSP and AMA1. Part B: safety, immunogenicity and protective efficacy of the CSP component

Background

A protective malaria vaccine will likely need to elicit both cell-mediated and antibody responses. As adenovirus vaccine vectors induce both these responses in humans, a Phase 1/2a clinical trial was conducted to evaluate the efficacy of an adenovirus serotype 5-vectored malaria vaccine against sporozoite challenge.

Methodology/Principal Findings

NMRC-MV-Ad-PfC is an adenovirus vector encoding the Plasmodium falciparum 3D7 circumsporozoite protein (CSP). It is one component of a two-component vaccine NMRC-M3V-Ad-PfCA consisting of one adenovector encoding CSP and one encoding apical membrane antigen-1 (AMA1) that was evaluated for safety and immunogenicity in an earlier study (see companion paper, Sedegah et al). Fourteen Ad5 seropositive or negative adults received two doses of NMRC-MV-Ad-PfC sixteen weeks apart, at particle units per dose. The vaccine was safe and well tolerated. All volunteers developed positive ELISpot responses by 28 days after the first immunization (geometric mean 272 spot forming cells/million[sfc/m]) that declined during the following 16 weeks and increased after the second dose to levels that in most cases were less than the initial peak (geometric mean 119 sfc/m). CD8+ predominated over CD4+ responses, as in the first clinical trial. Antibody responses were poor and like ELISpot responses increased after the second immunization but did not exceed the initial peak. Pre-existing neutralizing antibodies (NAb) to Ad5 did not affect the immunogenicity of the first dose, but the fold increase in NAb induced by the first dose was significantly associated with poorer antibody responses after the second dose, while ELISpot responses remained unaffected. When challenged by the bite of P. falciparum-infected mosquitoes, two of 11 volunteers showed a delay in the time to patency compared to infectivity controls, but no volunteers were sterilely protected.

Significance

The NMRC-MV-Ad-PfC vaccine expressing CSP was safe and well tolerated given as two doses, but did not provide sterile protection.

Trial Registration

ClinicalTrials.gov {"type":"clinical-trial","attrs":{"text":"NCT00392015","term_id":"NCT00392015"}}NCT00392015     

Mechanism of nodal flow: a conserved symmetry breaking event in left-right axis determination

The leftward flow in extraembryonic fluid is critical for the initial determination of the left-right axis of mouse embryos. It is unclear if this is a conserved mechanism among other vertebrates and how the directionality of the flow arises from the motion of cilia. In this paper, we show that rabbit and medakafish embryos also exhibit a leftward fluid flow in their ventral nodes. In all cases, primary monocilia present a clockwise rotational-like motion. Observations of defective ciliary dynamics in mutant mouse embryos support the idea that the posterior tilt of the cilia during rotational-like beating can explain the leftward fluid flow. Moreover, we show that this leftward flow may produce asymmetric distribution of exogenously introduced proteins, suggesting morphogen gradients as a subsequent mechanism of left-right axis determination. Finally, we experimentally and theoretically characterize under which conditions a morphogen gradient can arise from the flow.     

Alterations of the glutathione redox state improve apical meristem structure and somatic embryo quality in white spruce (Picea glauca)

In white spruce, an improvement of somatic embryo number and quality can be achieved through experimental manipulations of the endogenous levels of reduced (GSH) and oxidized (GSSG) glutathione. An optimal protocol for embryo production included an initial application of GSH in the maturation medium, followed by replacement with GSSG during the remaining maturation period. Under these conditions, the overall embryo population more than doubled, and the percentage of fully developed embryos increased from 22% to almost 70%. These embryos showed improved post-embryonic growth and conversion frequency. Structural studies revealed remarkable differences between embryo types, especially in storage product deposition pattern and organization of the shoot apical meristem (SAM). Compared with their control counterparts, glutathione-treated embryos accumulated a larger amount of starch during the early stages of development, and more protein and lipid bodies during the second half of development. Differences were also noted in the organization of SAMs. Shoot meristems of control embryos were poorly organized and were characterized by the presence of intercellular spaces, which caused separation of the subapical cells. Glutathione-treated embryos had well-organized meristems composed of tightly packed cells which lack large vacuoles. The improved organization of the shoot apical meristems in treated embryos was ascribed to a lower production of ethylene. Differences in meristem structure between control and treated embryos were also related to the localization pattern of HBK1, a shoot apical meristem 'molecular marker' gene with preferential expression to the meristematic cells of the shoot pole. Expression of this gene, which was localized to the apical cells in control embryos, was extended to the subapical cells of treated embryos. Overall, it appears that meristem integrity and embryo quality are under the direct control of the glutathione redox state.     

Oxygen-bound Hell's gate globin I by classical versus LB nanotemplate method

X‐ray atomic structure of recombinant Hell's gate globin I (HGbI) from Methylacidophilum infernorum was calculated from the X‐ray diffraction data of two different types of crystals: obtained by classical hanging drop and by LB nanotemplate method under the same crystallization conditions. After the accurate comparison of crystallographic parameters and electron density maps of two structures they appears to be quite similar, while the quality of the crystals grown by LB nanotemplate method was higher then of those grown by classical method. Indeed, the resolution of the LB crystal structure was 1.65 Å, while classical crystals showed only 3.2 Å resolution. Moreover, the reproducibility of this result in the case of LB crystals was much better—nine crystals from 10 gave the same structural results, while only two of 10 classical crystals were appropriate for the X‐ray structure resolution. J. Cell. Biochem. 113: 2543–2548, 2012. © 2012 Wiley Periodicals, Inc.     

Impacts of very warm temperature on egg production rates of three Acartiidae (Crustacea,Copepoda) in a Northern African lagoon

The daily Egg Production Rate (EPR) of the three Acartiidae copepods namely Acartia clausi, Paracartia latisetosa and Paracartia grani in the North Lagoon of Tunis was compared to temperature and food availability every season from March, 2003 to February, 2004 corresponding to the major seasonal peaks of their abundance and over a 20-days period. The daily EPR was evaluated by assuming a direct correlation with chlorophyll a, particulate organic carbon (POC), and some easily extractable macromolecular compounds from the seston, such as proteins, carbohydrates and lipids. The results showed significant differences in EPR between seasons and species. Temperature and salinity negatively affected the fecundity of A. clausi and positively that of P. latisetosa and P. grani. The A. clausi EPR was supported by chlorophyll a and sestonic proteins while that of P. latisetosa and P. grani correlated with POC suggesting that these two taxa feed on microzooplankton and detritus more than on phytoplankton. Overall, EPR data showed potential population recruitment evidently the highest in P. latisetosa in summer, P. grani in autumn and A. clausi in winter. Our results indicate that temperature and food quality are the determining factors of both abundance and reproduction of the copepods under study.