Synthese d'Oligodesoxyribonucleotides sur Support de Gel de Silice par la Methode au Phosphotriester

Abstract

A method of oligonucleotide synthesis was developped on a silica gel support by the phosphotriester approach. Using this method, the nonanucleoside octaphosphate dT(pT)₈ was synthetized in 28% yield.     

Genetic inactivation of NPC1L1 protects against sitosterolemia in mice lacking ABCG5/ABCG8

Mice lacking Niemann-Pick C1-Like 1 (NPC1L1) (NPC1L1(-/-)mice) exhibit a defect in intestinal absorption of cholesterol and phytosterols. However, wild-type (WT) mice do not efficiently absorb and accumulate phytosterols either. Cell-based studies show that NPC1L1 is a much weaker transporter for phytosterols than cholesterol. In this study, we examined the role of NPC1L1 in phytosterol and cholesterol trafficking in mice lacking ATP-binding cassette (ABC) transporters G5 and G8 (G5/G8(-/-) mice). G5/G8(-/-) mice develop sitosterolemia, a genetic disorder characterized by the accumulation of phytosterols in blood and tissues. We found that mice lacking ABCG5/G8 and NPC1L1 [triple knockout (TKO) mice] did not accumulate phytosterols in plasma and the liver. TKO mice, like G5/G8(-/-) mice, still had a defect in hepatobiliary cholesterol secretion, which was consistent with TKO versus NPC1L1(-/-) mice exhibiting a 52% reduction in fecal cholesterol excretion. Because fractional cholesterol absorption was reduced similarly in NPC1L1(-/-) and TKO mice, by subtracting fecal cholesterol excretion in TKO mice from NPC1L1(-/-) mice, we estimated that a 25g NPC1L1(-/-) mouse may secrete about 4 mumol of cholesterol daily via the G5/G8 pathway. In conclusion, NPC1L1 is essential for phytosterols to enter the body in mice.     

Does operational sex ratio influence relative strength of purging selection in males versus females?

According to theory, sexual selection in males may efficiently purge mutation load of sexual populations, reducing or fully compensating ‘the cost of males’. For this to occur, mutations not only need to be deleterious to both sexes, they also must affect males more than females. A frequently overlooked problem is that relative strength of selection on males versus females may vary between environments, with social conditions being particularly likely to affect selection in males and females differently. Here, we induced mutations in red flour beetles (Tribolium castaneum) and tested their effect in both sexes under three different operational sex ratios (1:2, 1:1 and 2:1). Induced mutations decreased fitness of both males and females, but their effect was not stronger in males. Surprisingly, operational sex ratio did not affect selection against deleterious mutations nor its relative strength in the sexes. Thus, our results show no support for the role of sexual selection in the evolutionary maintenance of sex.     

Housing condition alters immunological and reproductive responses to day length in Siberian hamsters (Phodopus sungorus)

During winter, increased thermoregulatory demands coincide with limited food availability necessitating physiological tradeoffs among expensive physiological processes resulting in seasonal breeding among small mammals. In the laboratory, short winter-like day lengths induce regression of the reproductive tract, but also enhance many aspects of immune function. It remains unspecified the extent to which bolstered immune responses in short days represent enhanced immune function per se compared to long days or represents energetic disinhibition mediated by the regression of the reproductive tract. Cohabitation of male Siberian hamsters with intact female conspecifics can block short-day reproductive regression. We sought to determine whether female cohabitation could also block the enhanced immune function associated with short days. Adult male Siberian hamsters were housed in long or short day lengths in one of three housing conditions: (1) single-housed, (2) housed with a same sex littermate, or (3) housed with an ovariectomized female. Delayed-type hypersensitivity (DTH) responses were assessed after 8 weeks of photoperiod treatment. Housing with an ovariectomized female was not sufficient to block short-day reproductive regression, but prevented short-day enhancement of DTH responses. Housing with a male littermate did not alter reproductive or immune responses in either photoperiod. These data suggest that short day enhancement of immune function is independent of photoperiod-mediated changes in the reproductive system.     

Stromal upregulation of lateral epithelial adhesions: Gene expression analysis of signalling pathways in prostate epithelium

Background  

Stromal signalling increases the lateral cell adhesions of prostate epithelial cells grown in 3D culture. The aim of this study was to use microarray analysis to identify significant epithelial signalling pathways and genes in this process.     

Quantitative trait loci controlling light and hormone response in two accessions of Arabidopsis thaliana

We have mapped quantitative trait loci (QTL) responsible for natural variation in light and hormone response between the Cape Verde Islands (Cvi) and Landsberg erecta (Ler) accessions of Arabidopsis thaliana using recombinant inbred lines (RILs). Hypocotyl length was measured in four light environments: white, blue, red, and far-red light and in the dark. In addition, white light plus gibberellin (GA) and dark plus the brassinosteroid biosynthesis inhibitor brassinazole (BRZ) were used to detect hormone effects. Twelve QTL were identified that map to loci not previously known to affect light response, as well as loci where candidate genes have been identified from known mutations. Some QTL act in all environments while others show genotype-by-environment interaction. A global threshold was established to identify a significant epistatic interaction between two loci that have few main effects of their own. LIGHT1, a major QTL, has been confirmed in a near isogenic line (NIL) and maps to a new locus with effects in all light environments. The erecta mutation can explain the effect of the HYP2 QTL in the blue, BRZ, and dark environments, but not in far-red. LIGHT2, also confirmed in an NIL, has effects in white and red light and shows interaction with GA. The phenotype and map position of LIGHT2 suggest the photoreceptor PHYB as a candidate gene. Natural variation in light and hormone response thus defines both new genes and known genes that control light response in wild accessions.     

Biological Effects of Trichoderma harzianum Peptaibols on Mammalian Cells

Trichoderma species isolated from water-damaged buildings were screened for toxicity by using boar sperm cells as indicator cells. The crude methanolic cell extract from Trichoderma harzianum strain ES39 inhibited the boar sperm cell motility at a low exposure concentration (50% effective concentration, 1 to 5 μg [dry weight] ml of extended boar semen⁻¹). The same exposure concentration depleted the boar sperm cells of NADH₂. Inspection of the exposed boar sperm cells by transmission electron microscopy revealed damage to the plasma membrane. By using the black lipid membrane technique, it was shown that the semipurified metabolites (eluted from a SepPak C₁₈ cartridge) of T. harzianum strain ES39 induced voltage-dependent conductivity. The high-performance liquid chromatography-purified metabolites of T. harzianum strain ES39 dissipated the mitochondrial membrane potential (Δψ_m) of human lung epithelial carcinoma cells (cell line A549). The semipurified metabolites (eluted from a SepPak C₁₈ cartridge) of T. harzianum strain ES39 were analyzed by mass spectrometry (MS). Matrix-assisted laser desorption ionization and nanoflow electrospray ionization MS revealed five major peptaibols, each of which contained 18 residues and had a mass ranging from 1,719 to 1,775 Da. Their partial amino acid sequences were determined by collision-induced dissociation tandem MS.     

Crystal structures of interleukin-2 tyrosine kinase and their implications for the design of selective inhibitors

Interleukin-2 tyrosine kinase, Itk, is an important member of the Tec family of non-receptor tyrosine kinases that play a central role in signaling through antigen receptors such as the T-cell receptor, B-cell receptor, and Fcepsilon. Selective inhibition of Itk may be an important way of modulating many diseases involving heightened or inappropriate activation of the immune system. In addition to an unliganded nonphophorylated Itk catalytic kinase domain, we determined the crystal structures of the phosphorylated and nonphosphorylated kinase domain bound to staurosporine, a potent broad-spectrum kinase inhibitor. These structures are useful for the design of novel, highly potent and selective Itk inhibitors and provide insight into the influence of inhibitor binding and phosphorylation on the conformation of Itk.     

Venturia inaequalis: the causal agent of apple scab

The fungus Venturia inaequalis infects members of the Maloideae, and causes the disease apple scab, the most important disease of apple worldwide. The early elucidation of the gene-for-gene relationship between V. inaequalis and its host Malus has intrigued plant pathologists ever since, with the identification of 17 resistance (R)-avirulence (Avr) gene pairings. The Avr gene products are presumably a subset of the total effector arsenal of V. inaequalis (predominantly proteins secreted in planta assumed to facilitate infection). The supposition that effectors from V. inaequalis act as suppressors of plant defence is supported by the ability of the pathogen to penetrate the cuticle and differentiate into large pseudoparenchymatous structures, termed stromata, in the subcuticular space, without the initiation of an effective plant defence response. If effectors can be identified that are essential for pathogenicity, the corresponding R genes will be durable and would add significant value to breeding programmes. An R gene cluster in Malus has been cloned, but no V. inaequalis effectors have been characterized at the molecular level. However, the identification of effectors is likely to be facilitated by the resolution of the whole genome sequence of V. inaequalis. TAXONOMY: Teleomorph: Venturia inaequalis Cooke (Wint.); Kingdom Fungi; Phylum Ascomycota; Subphylum Euascomycota; Class Dothideomycetes; Family Venturiaceae; genus Venturia; species inaequalis. Anamorph: Fusicladium pomi (Fr.) Lind or Spilocaea pomi (Fr.). LIFE CYCLE: V. inaequalis is a hemibiotroph and overwinters as pseudothecia (sexual fruiting bodies) following a phase of saprobic growth in fallen leaf tissues. The primary inoculum consists of ascospores, which germinate and penetrate the cuticle. Stromata are formed above the epidermal cells but do not penetrate them. Cell wall-degrading enzymes are only produced late in the infection cycle, raising the as yet unanswered question as to how V. inaequalis gains nutrients from the host. Conidia (secondary inoculum) arise from the upper surface of the stromata, and are produced throughout the growing season, initiating multiple rounds of infection. VENTURIA INAEQUALIS AS A MODEL PATHOGEN OF A WOODY HOST: V. inaequalis can be cultured and is amenable to crossing in vitro, enabling map-based cloning strategies. It can be transformed readily, and functional analyses can be conducted by gene silencing. Expressed sequence tag collections are available to aid in gene identification. These will be complemented by the whole genome sequence, which, in turn, will contribute to the comparative analysis of different races of V. inaequalis and plant pathogens within the Dothideomycetes.