Novel Plasmodium falciparum Maurer's clefts protein families implicated in the release of infectious merozoites

The pathogenicity of the most deadly human malaria parasite, Plasmodium falciparum, relies on the export of virulence factors to the surface of infected erythrocytes. A novel membrane compartment, referred to as Maurer's clefts, is transposed to the host erythrocyte, acting as a marshal platform in the red blood cell cytoplasm, for exported parasite proteins addressed to the host cell plasma membrane. We report here the characterization of three new P. falciparum multigene families organized in 9 highly conserved clusters with the Pfmc‐2tm genes in the subtelomeric regions of parasite's chromosomes and expressed at early trophozoite stages. Like the PfMC‐2TM proteins, the PfEPF1, 3 and 4 proteins encoded by these families are exported to the Maurer's clefts, as peripheral or integral proteins of the Maurer's cleft membrane and largely exposed to the red cell cytosolic face of this membrane. A promoter titration approach was used to question the biological roles of these P. falciparum‐specific exported proteins. Using the Pfepf1 family promoter, we observed the specific downregulation of all four families, correlating with the inefficient release of merozoites while the parasite intra‐erythrocytic maturation and Maurer's clefts morphology were not impacted.     

Generation of transgenic mice that conditionally express microRNA miR‐145

MicroRNAs are modulators of cellular phenotypes and their functions contribute to development, homeostasis, and disease. miR‐145 is a conserved microRNA that has been implicated in regulating an array of phenotypes. These include supporting smooth muscle differentiation, repression of stem cell pluripotency, and inhibition of tumor growth and metastasis. Previously, our lab demonstrated that miR‐145 acts to suppress cardiac fibrosis through inhibition of the TGF‐β signaling pathway. The range of effects that miR‐145 has on different cell types makes it an attractive microRNA for further study. Here we describe the generation of transgenic mice that conditionally express miR‐145 through Cre recombinase‐mediated activation. Characterization of individual founder lines indicates that overexpression of miR‐145 in the developing cardiovascular system has detrimental effects, with three independent miR‐145 transgenic lines exhibiting Cre‐dependent lethality. Expression analysis demonstrates that the transgene is robustly expressed and our analysis reveals a novel downstream target of miR‐145, Tnnt2. The miR‐145 transgenic mice represent a valuable tool to understand the role of miR‐145 in diverse cell types and to address its potential as a therapeutic mediator for the treatment of disease.     

Maternal dietary omega-3 fatty acid intake increases resolvin and protectin levels in the rat placenta

Placental inflammation is associated with several pregnancy disorders. Inflammation is limited by anti-inflammatory and proresolving mechanisms, the latter partly mediated by resolvins and protectins derived from omega-3 polyunsaturated fatty acids (n-3PUFA). We examined effects of dietary n-3PUFAs on levels of resolvins, protectins, and lipoxygenase (ALOX) enzymes in the rat placenta. Rats consumed standard (Std) or high n-3PUFA (Hn3) diets from day 1 of pregnancy; tissues were collected on day 17 or 22 (term = day 23). Maternal Hn3 diet increased resolvin and protectin precursors, 18R/S-HEPE (P < 0.001), and 17R/S-HDHA (P < 0.01) at both days. Resolvins (17R-RvD1 and RvD1) increased at day 22 (P < 0.001) after Hn3 consumption, coincident with higher Alox15b and Alox5 mRNA expression, while RvD2 increased at both days (P < 0.05). Protectins, PD1, and 10S,17S-DiHDHA increased over late gestation (P < 0.001), coincident with higher Alox15 mRNA expression (P < 0.001) and further increased with Hn3 diet (P < 0.05). Maternal systemic and placental proinflammatory mediators were not suppressed by Hn3 diet; systemic IL1β, placental Il1β, and Il6 mRNA expression increased marginally with Hn3 at day 22 (P < 0.001), while Ptgs1 (Cox1) expression increased both days (P < 0.05). Our data indicate that maternal n-3PUFA supplementation enhances expression of enzymes in the n-3PUFA metabolic pathway and increases placental levels of resolvins and protectins.     

Characterization of Newcastle Disease Viruses in Wild and Domestic Birds in Luxembourg from 2006 to 2008

Newcastle disease virus (NDV) is one of the most important viral diseases of birds. Wild birds constitute a natural reservoir of low-virulence viruses, while poultry are the main reservoir of virulent strains. Exchange of virus between these reservoirs represents a risk for both bird populations. Samples from wild and domestic birds collected between 2006 and 2010 in Luxembourg were analyzed for NDV. Three similar avirulent genotype I strains were found in ducks during consecutive years, suggesting that the virus may have survived and spread locally. However, separate introductions cannot be excluded, because no recent complete F gene sequences of genotype I from other European countries are available. Detection of vaccine-like strains in wild waterbirds suggested the spread of vaccine strains, despite the nonvaccination policy in Luxembourg. Among domestic birds, only one chicken was positive for a genotype II strain differing from the LaSota vaccine and exhibiting a so-far-unrecognized fusion protein cleavage site of predicted low virulence. Three genotype VI strains from pigeons were the only virulent strains found. The circulation of NDV in wild and free-ranging domestic birds warrants continuous surveillance because of increased concern that low-virulence wild-bird viruses could become more virulent in domestic populations.     

Methionine sulfoxide reduction in ciliates: Characterization of the ready-to-use methionine sulfoxide-R-reductase genes in Euplotes

Genes encoding the enzyme methionine sulfoxide reductase type B, specific to the reduction of the oxidized methionine-R form, were characterized from the expressed (macronuclear) genome of two ecologically separate marine species of Euplotes, i.e. temperate water E. raikovi and polar water E. nobilii. Both species were found to contain a single msrB gene with a very simple structural organization encoding a protein of 127 (E. raikovi) or 126 (E. nobilii) amino acid residues that belongs to the group of zinc-containing enzymes. Both msrB genes are constitutively expressed, suggesting that the MsrB enzyme plays an essential role in repairing oxidative damages that appear to be primarily caused by physiological cell aging in E. raikovi and by interactions with an O₂ saturated environment in E. nobilii.     

Quaternary land bridges have not been universal conduits of gene flow

Quaternary climate oscillations are a well‐known driver of animal diversification, but their effects are most well studied in areas where glaciations lead to habitat fragmentation. In large areas of the planet, however, glaciations have had the opposite effect, but here their impacts are much less well understood. This is especially true in Southeast Asia, where cyclical changes in land distribution have generated enormous land expansions during glacial periods. In this study, we selected a panel of five songbird species complexes covering a range of ecological specificities to investigate the effects Quaternary land bridges have had on the connectivity of Southeast Asian forest biota. Specifically, we combined morphological and bioacoustic analysis with an arsenal of population genomic and modelling approaches applied to thousands of genome‐wide DNA markers across a total of more than 100 individuals. Our analyses show that species dependent on forest understorey exhibit deep differentiation between Borneo and western Sundaland, with no evidence of gene flow during the land bridges accompanying the last 1–2 ice ages. In contrast, dispersive canopy species and habitat generalists have experienced more recent gene flow. Our results argue that there remains much cryptic species‐level diversity to be discovered in Southeast Asia even in well‐known animal groups such as birds, especially in nondispersive forest understorey inhabitants. We also demonstrate that Quaternary land bridges have not been equally suitable conduits of gene flow for all species complexes and that life history is a major factor in predicting relative population divergence time across Quaternary climate fluctuations.