Human T cell leukemia virus type I prevents cell surface expression of the T cell receptor through down-regulation of the CD3-gamma, -delta, -epsilon, and -zeta genes

Infection and transformation by human T cell leukemia virus type I (HTLV-I) up-regulates expression of several inducible genes including those coding for cytokines involved in the proliferation of normal and leukemic T cells. We demonstrate that HTLV-I can also shut off expression of the CD3-gamma, delta, epsilon, and zeta genes that code for the constant elements of the TCR for Ag. In addition, the T cell-specific CD3-epsilon enhancer was found to be inactive in a HTLV-I-infected T cell clone. This HTLV-I-infected T cell clone (827-p19-II) that could be cultured in the absence of IL-2 lacked the CD3 proteins but did express the TCR-alpha and -beta proteins intracellularly. In the absence of the CD3-gamma, delta, epsilon, and zeta polypeptide chains the disulfide bridged TCR-alpha/beta heterodimer was not formed and the Ag receptor did not appear at the cell surface. These results allowed two major conclusions: first, HTLV-I infection has an effect on the T cell specific regulatory elements that coordinately regulate CD3-gamma, delta, epsilon, and zeta expression and second, the CD3-gamma, delta, epsilon, and zeta proteins are necessary for formation and routing the variable TCR-alpha/beta (or -gamma/delta) heterodimer to the human T cell surface.     

Introduction of T cell receptor (TCR)-alpha cDNA has differential effects on TCR-gamma delta/CD3 expression by PEER and Lyon-1 cells

A TCR heterodimer composed of a TCR gamma-chain and a TCR delta-chain was found to be expressed in association with CD3 by a small population of human peripheral blood T cells, thymocytes, and certain leukemic T cell lines. The leukemic T cell lines PEER and Lyon-1 express such a TCR-gamma delta/CD3 complex at the cell surface. In addition, PEER and Lyon-1 cells transcribe a productively rearranged TCR-beta gene. Introduction of TCR alpha-chain cDNA of human or murine origin resulted in cell surface expression of a TCR-alpha beta/CD3 complex on PEER and Lyon-1 cells. The expression of the TCR-gamma delta/CD3 complex on PEER cells was not affected by introduction of TCR-alpha cDNA. In contrast, introduction of a TCR-alpha cDNA and expression of the TCR-alpha beta/CD3 complex in Lyon-1 cells resulted in the disappearance of the TCR-gamma delta/CD3 complex. These data were confirmed by indirect immunofluorescence, at the protein level and by gene expression analysis. Triggering of the TCR-alpha beta/CD3 complexes by anti-CD3 mAb or anti-TCR mAb resulted in increased internal Ca2+ levels, indicating that these receptors were functional in signal transduction. These results indicate that, besides TCR gene rearrangements, membrane expression of TCR-alpha beta heterodimers may be important in regulating TCR-gamma delta cell surface expression.     

Cotton,cowpea and sesame are alternative crops to cucurbits in soils naturally infested with Monosporascus cannonballus

Monosporascus cannonballus is an important cucurbit root pathogen, which has been reported in the main production areas of melon and watermelon in Brazil and worldwide and potentially capable to colonize roots of different species. Crop rotation is considered an effective management strategy to prevent this disease. The aim of this study was to evaluate the response of different crops, pumpkin, cotton, cowpea, sesame, watermelon, melon, corn, cucumber, sorghum and tomato, to the infection of this pathogen. Seedlings were transplanted into plastic containers with an inoculum concentration of 20 colony‐forming units (CFU) g^?1 of M. cannonballus. Fifty days after transplanting, the variables analysed were the degree of disease severity on the root system and the frequency of reisolation. On cucurbits, the results demonstrated different degrees of susceptibility among crops and cultivars, being melon and watermelon the most sensitive species. In contrast, Cucurbita cultivars were the most tolerant. Regarding non‐cucurbit crops, maize, sorghum and tomato presented root discoloration and M. cannonballus was reisolated from roots. Cotton, cowpea and sesame cultivars were not affected by the pathogen, so they can be considered as alternative crops to be cultivated, or in rotation with cucurbits, in M. cannonballus infested soils.     

Normal CA1 Place Fields but Discoordinated Network Discharge in a Fmr1-Null Mouse Model of Fragile X Syndrome

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Phylogeographic structure of <Emphasis Type="Italic">Spondias tuberosa</Emphasis> Arruda Câmara (Anacardiaceae): seasonally dry tropical forest as a large and continuous refuge

Spondias tuberosa occurs in the Caatinga domain (seasonally dry tropical forest biome) of north-eastern Brazil, a large biome with ecogeographic regions that may have modelled the population structure of the species. Here we studied the phylogeographic pattern of S. tuberosa using sequences of the accD-psaI plastid region and six SSR markers in individuals distributed across 20 localities. The results for accD-psaI demonstrated nine haplotypes: some of which were exclusive to Caatinga ecoregions, whereas others were found in all localities. Spatial analysis of molecular variance revealed two groups (F_ct?=?0.34, P?<?0.0039) with 33.91% variation between them. The SSR analyses displayed 2–5 alleles at each locus, some of which were unique to certain localities. As in the accD-psaI region, the population structure obtained using SSR markers fell into two groups: (1) a large group containing the majority of the geographic region of Caatinga and (2) a small group near the Atlantic forest. We demonstrate the population structure of S. tuberosa, identifying the Caatinga as large, continuous refuge and the region near the interface between the Caatinga and the Atlantic forest as second refuge.     

Percent of oxygen saturation of arterial hemoglobin among Bolivian Aymara at 3,900–4,000 m

A range of variation in percent of oxygen saturation of arterial hemoglobin (SaO₂) among healthy individuals at a given high altitude indicates differences in physiological hypoxemia despite uniform ambient hypoxic stress. In populations native to the Tibetan plateau, a significant portion of the variance is attributable to additive genetic factors, and there is a major gene influencing SaO₂. To determine whether there is genetic variance in other high-altitude populations, we designed a study to test the hypothesis that additive genetic factors contribute to phenotypic variation in SaO₂ among Aymara natives of the Andean plateau, a population geographically distant from the Tibetan plateau and with a long, separate history of high-altitude residence. The average SaO₂ of 381 Aymara at 3,900–4,000 m was 92 ± 0.15% (SEM) with a range of 84–99%. The average was 2.6% higher than the average SaO₂ of a sample of Tibetans at 3,800–4,065 m measured with the same techniques. Quantitative genetic analyses of the Aymara sample detected no significant variance attributable to genetic factors. The presence of genetic variance in SaO₂ in the Tibetan sample and its absence in the Aymara sample indicate there is potential for natural selection on this trait in the Tibetan but not the Aymara population. Am J Phys Anthropol 108:41–51, 1999. © 1999 Wiley-Liss, Inc.     

Direct classification of related species of fungal endophytes (Epichloë spp.) using visible and near-infrared spectroscopy and multivariate analysis

The aim of this work was to investigate the potential of visible and near-infrared (Vis-NIR) reflectance spectroscopy for the classification of three morphologically similar species of fungal endophytes of grasses. Vis-NIR spectra (400–2498 nm) from 34 isolates of Epichloë sylvatica , 32 of Epichloë typhina and 38 of Epichloë festucae were recorded directly from fresh mycelium growing in potato dextrose agar plates. Multivariate procedures applied to the spectral data were discriminant modified partial least squares regression, soft independent modelling of class analogy and discriminant partial least squares regressions (PLS1, PLS2). Several types of data pretreatments were tested to develop the classification models. The best predictive models were achieved with PLS2 analysis; with this method, 90% of E. typhina and 100% of E. festucae and E. sylvatica external validation samples were successfully classified. These results show the potential of Vis-NIR spectroscopy combined with multivariate analysis as a rapid method for classifying morphologically similar species of filamentous fungi.     

Interaction between the N-terminal SH3 domain of Nck-alpha and CD3-epsilon-derived peptides: non-canonical and canonical recognition motifs

The first SH3 domain (SH3.1) of Nckalpha specifically recognizes the proline-rich region of CD3varepsilon, a subunit of the T cell receptor complex. We have solved the NMR structure of Nckalpha SH3.1 that shows the characteristic SH3 fold consisting of two antiparallel beta-sheets tightly packed against each other. According to chemical shift mapping analysis, a peptide encompassing residues 150-166 of CD3varepsilon binds at the canonical SH3 binding site. An exhaustive comparison with the structures of other SH3 domains able and unable to bind CD3varepsilon reveals that Nckalpha SH3.1 recognises a non-canonical PxxPxxDY motif that orientates at the binding site as a class II ligand. A positively charged residue (K/R) at position -2 relative to the WW sequence at the beginning of strand beta3 is crucial for PxxDY recognition. A 14-mer optimised Nckalpha SH3.1 ligand was found using a multi-substitution approach. Based on NMR data, this improved ligand binds Nckalpha SH3.1 through a PxxPxRDY motif that combines specific stabilising interactions corresponding to both canonical class II, PxxPx(K/R), and non-canonical PxxPxxDY motifs. This explains its higher capacity for Nckalpha SH3.1 binding relative to the wild type sequence.