Peroxisomal multifunctional protein-2: the enzyme, the patients and the knockout mouse model

The mammalian multifunctional protein-2 (MFP-2, also called multifunctional enzyme 2, D-bifunctional enzyme or 17-beta-estradiol dehydrogenase type IV) was identified by several groups about a decade ago. It plays a central role in peroxisomal beta-oxidation as it handles most, if not all, peroxisomal beta-oxidation substrates. Deficiency of this enzyme in man causes a severe developmental syndrome with abnormalities in several organs but in particular in the brain, leading to death within the first year of life. Accumulation of branched-long-chain fatty acids and very-long-chain fatty acids and a disturbed synthesis of bile acids were documented in these patients. A mouse model with MFP-2 deficiency only partly phenocopies the human disease. Although the expected metabolic abnormalities are present, no neurodevelopmental aberrations are observed. However, the survival of these mice into adulthood allowed to document the importance of this enzyme for the normal functioning of the brain, eyes and testis. In the present review, the identification and biochemical characteristics of MFP-2, and the consequences of MFP-2 dysfunction in humans and in mice will be discussed.     

Multilocus patterns of nucleotide diversity, linkage disequilibrium and demographic history of Norway spruce [Picea abies (L.) Karst

DNA polymorphism at 22 loci was studied in an average of 47 Norway spruce [Picea abies (L.) Karst.] haplotypes sampled in seven populations representative of the natural range. The overall nucleotide variation was limited, being lower than that observed in most plant species so far studied. Linkage disequilibrium was also restricted and did not extend beyond a few hundred base pairs. All populations, with the exception of the Romanian population, could be divided into two main domains, a Baltico-Nordic and an Alpine one. Mean Tajima's D and Fay and Wu's H across loci were both negative, indicating the presence of an excess of both rare and high-frequency-derived variants compared to the expected frequency spectrum in a standard neutral model. Multilocus neutrality tests based on D and H led to the rejection of the standard neutral model and exponential growth in the whole population as well as in the two main domains. On the other hand, in all three cases the data are compatible with a severe bottleneck occurring some hundreds of thousands of years ago. Hence, demographic departures from equilibrium expectations and population structure will have to be accounted for when detecting selection at candidate genes and in association mapping studies, respectively.     

Characterization of new microsatellite loci isolated from Santiria trimera (Burseraceae)

? Premise of the study: To study the genetic structure among three morphotypes of an African rainforest tree species, Santiria trimera, nuclear microsatellite markers were isolated and characterized. ? Methods and Results: Seven polymorphic loci were isolated using a pyrosequencing-based protocol and successfully amplified on three different morphotypes of S. trimera. For six of the seven loci, there is at least one private allele for one of the three morphotypes. The mean effective number of alleles is about four for each of the three morphotypes. ? Conclusions: These microsatellite markers are promising to explore the genetic delimitation among sympatric morphotypes found in Gabonese forests and to study the spatial genetic structure within each gene pool.     

Disruption and stabilization of β-cell actin microfilaments differently influence insulin secretion triggered by intracellular Ca2+ mobilization or store-operated Ca2+ entry

Latrunculin depolymerizes and jasplakinolide polymerizes β-cell actin microfilaments. Both increase insulin secretion when Ca(2+) enters β-cells during depolarization by glucose, sulfonylureas or potassium. Mouse islets were held hyperpolarized with diazoxide, and stimulated with acetylcholine to test the role of microfilaments in insulin secretion triggered by intracellular Ca(2+) mobilization and store-operated Ca(2+) entry (SOCE). Jasplakinolide slightly attenuated Ca(2+) mobilization and did not affect SOCE, but consistently inhibited the attending insulin secretion. Latrunculin did not affect Ca(2+) changes induced by acetylcholine, but consistently increased insulin secretion, its effect being larger in response to Ca(2+) entry than to Ca(2+) mobilization. Microfilaments have thus a distinct impact on exocytosis of insulin granules depending on the source of triggering Ca(2+).     

HLA-B7-restricted EBV-specific CD8+ T cells are dysregulated in multiple sclerosis

It was hypothesized that the EBV-specific CD8(+) T cell response may be dysregulated in multiple sclerosis (MS) patients, possibly leading to a suboptimal control of this virus. To examine the CD8(+) T cell response in greater detail, we analyzed the HLA-A2-, HLA-B7-, and HLA-B8-restricted EBV- and CMV-specific CD8(+) T cell responses in a high number of MS patients and control subjects using tetramers. Content in cytolytic granules, as well as cytotoxic activity, of EBV- and CMV-specific CD8(+) T cells was assessed. We found that MS patients had a lower or a higher prevalence of HLA-A2 and HLA-B7, respectively. Using HLA class I tetramers in HLA-B7(+) MS patients, there was a higher prevalence of MS patients with HLA-B*0702/EBV(RPP)-specific CD8(+) T cells ex vivo. However, the magnitude of the HLA-B*0702/EBV(RPP)-specific and HLA-B*0702/CMV(TPR)-specific CD8(+) T cell response (i.e., the percentage of tetramer(+) CD8(+) T cells in a study subject harboring CD8(+) T cells specific for the given epitope) was lower in MS patients. No differences were found using other tetramers. After stimulation with the HLA-B*0702/EBV(RPP) peptide, the production of IL-2, perforin, and granzyme B and the cytotoxicity of HLA-B*0702/EBV(RPP)-specific CD8(+) T cells were decreased. Altogether, our findings suggest that the HLA-B*0702-restricted viral (in particular the EBV one)-specific CD8(+) T cell response is dysregulated in MS patients. This observation is particularly interesting knowing that the HLA-B7 allele is more frequently expressed in MS patients and considering that EBV is associated with MS.     

Genome sequence of Weissella confusa LBAE C39-2, isolated from a wheat sourdough

Weissella confusa is a rod-shaped heterofermentative lactic acid bacterium from the family of Leuconostocaceae. Here we report the draft genome sequence of the strain W. confusa LBAE C39-2 isolated from a traditional French wheat sourdough.     

Sodium selenide toxicity is mediated by O2-dependent DNA breaks

Hydrogen selenide is a recurrent metabolite of selenium compounds. However, few experiments studied the direct link between this toxic agent and cell death. To address this question, we first screened a systematic collection of Saccharomyces cerevisiae haploid knockout strains for sensitivity to sodium selenide, a donor for hydrogen selenide (H(2)Se/HSe(-/)Se(2-)). Among the genes whose deletion caused hypersensitivity, homologous recombination and DNA damage checkpoint genes were over-represented, suggesting that DNA double-strand breaks are a dominant cause of hydrogen selenide toxicity. Consistent with this hypothesis, treatment of S. cerevisiae cells with sodium selenide triggered G2/M checkpoint activation and induced in vivo chromosome fragmentation. In vitro, sodium selenide directly induced DNA phosphodiester-bond breaks via an O(2)-dependent reaction. The reaction was inhibited by mannitol, a hydroxyl radical quencher, but not by superoxide dismutase or catalase, strongly suggesting the involvement of hydroxyl radicals and ruling out participations of superoxide anions or hydrogen peroxide. The (?)OH signature could indeed be detected by electron spin resonance upon exposure of a solution of sodium selenide to O(2). Finally we showed that, in vivo, toxicity strictly depended on the presence of O(2). Therefore, by combining genome-wide and biochemical approaches, we demonstrated that, in yeast cells, hydrogen selenide induces toxic DNA breaks through an O(2)-dependent radical-based mechanism.     

Human Haemato-Endothelial Precursors: Cord Blood CD34+ Cells Produce Haemogenic Endothelium

Embryologic and genetic evidence suggest a common origin of haematopoietic and endothelial lineages. In the murine embryo, recent studies indicate the presence of haemogenic endothelium and of a common haemato-endothelial precursor, the haemangioblast. Conversely, so far, little evidence supports the presence of haemogenic endothelium and haemangioblasts in later stages of development. Our studies indicate that human cord blood haematopoietic progenitors (CD34+45+144−), triggered by murine hepatocyte conditioned medium, differentiate into adherent proliferating endothelial precursors (CD144+CD105+CD146+CD31+CD45−) capable of functioning as haemogenic endothelium. These cells, proven to give rise to functional vasculature in vivo, if further instructed by haematopoietic growth factors, first switch to transitional CD144+45+ cells and then to haematopoietic cells. These results highlight the plasticity of haemato-endhothelial precursors in human post-natal life. Furthermore, these studies may provide highly enriched populations of human post-fetal haemogenic endothelium, paving the way for innovative projects at a basic and possibly clinical level.