Identifying landscape features associated with Rift Valley fever virus transmission, Ferlo region, Senegal, using very high spatial resolution satellite imagery.

INTRODUCTION: Dynamics of most of vector-borne diseases are strongly linked to global and local environmental changes. Landscape changes are indicators of human activities or natural processes that are likely to modify the ecology of the diseases. Here, a landscape approach developed at a local scale is proposed for extracting mosquito favourable biotopes, and for testing ecological parameters when identifying risk areas of Rift Valley fever (RVF) transmission. The study was carried out around Barkedji village, Ferlo region, Senegal. METHODS: In order to test whether pond characteristics may influence the density and the dispersal behaviour of RVF vectors, and thus the spatial variation in RVFV transmission, we used a very high spatial resolution remote sensing image (2.4 m resolution) provided by the Quickbird sensor to produce a detailed land-cover map of the study area. Based on knowledge of vector and disease ecology, seven landscape attributes were defined at the pond level and computed from the land-cover map. Then, the relationships between landscape attributes and RVF serologic incidence rates in small ruminants were analyzed through a beta-binomial regression. Finally, the best statistical model according to the Akaike Information Criterion corrected for small samples (AICC), was used to map areas at risk for RVF. RESULTS: Among the derived landscape variables, the vegetation density index (VDI) computed within a 500 m buffer around ponds was positively correlated with serologic incidence (p<0.001), suggesting that the risk of RVF transmission was higher in the vicinity of ponds surrounded by a dense vegetation cover. The final risk map of RVF transmission displays a heterogeneous spatial distribution, corroborating previous findings from the same area. CONCLUSIONS: Our results highlight the potential of very high spatial resolution remote sensing data for identifying environmental risk factors and mapping RVF risk areas at a local scale.

Ectopic expression of H-1 parvovirus NS1 protein induces alterations in actin filaments and cell death in human normal MRC-5 and transformed MRC-5 SV2 cells.

When grown in human cell lines, oncolytic H-1 parvovirus (H-1PV) replication preferentially occurs in transformed cells, which ultimately die upon infection. H-1PV-induced cytotoxicity is mainly due to P4 promoter-driven NS1 protein expression. Infection of untransformed cells generally does not induce deleterious effects because the P4 promoter is not activated. Here, we show that ectopic CMV-driven NS1 protein expression in normal human MRC-5 cells results in alterations of actin filaments and cell death, and both effects are prevented by a serine 473 mutation. The same substitution preserves actin filaments of transfected MRC-5 SV2 cells, that are MRC-5 transformed counterparts, but does not impair NS1-induced cytotoxicity.

Parvovirus H-1 induces cytopathic effects in breast carcinoma-derived cultures.

Parvovirus H-1 (H-1 PV) preferentially replicates in malignant cells resulting in their death by cytolysis. It has often been considered a potential candidate for use in novel anticancer therapy. To evaluate its potential in a model of natural tumors, we assayed in vitro the effect exerted by H-1 PV on short-term cultures derived from breast tumor samples freshly excised from patients. Our results show that H-1 PV effectively kills tumor-derived cells, whereas normal tissue-derived cells showed no H-1 PV-induced cytopathic effects (CPE). We also determined that the H-1 PV sensitivity (up to 67% sensitive cultures) is related with the quantities of virus assayed. We further examined the expression and phosphorylation state of the parvoviral nonstructural protein 1 (NS1), known to be associated with parvoviruses-induced CPE. Both appear to be impaired in normal tissue-derived cells and resistant cultures. Finally, we show that H-1 PV sensitivity in cultures correlates significantly with higher tumor grades (Nottingham combined histologic grade 2 or 3). This report confirms that H-1 PV can efficiently induce CPE in primary breast tumor cells in vitro. It identifies tumor characteristics representing potential criteria for recruiting patients for clinical evaluation of H-1 PV antitumor effects.

Scavenger chemokine (CXC motif) receptor 7 (CXCR7) is a direct target gene of HIC1 (hypermethylated in cancer 1).

The tumor suppressor gene HIC1 (Hypermethylated in Cancer 1) that is epigenetically silenced in many human tumors and is essential for mammalian development encodes a sequence-specific transcriptional repressor. The few genes that have been reported to be directly regulated by HIC1 include ATOH1, FGFBP1, SIRT1, and E2F1. HIC1 is thus involved in the complex regulatory loops modulating p53-dependent and E2F1-dependent cell survival and stress responses. We performed genome-wide expression profiling analyses to identify new HIC1 target genes, using HIC1-deficient U2OS human osteosarcoma cells infected with adenoviruses expressing either HIC1 or GFP as a negative control. These studies identified several putative direct target genes, including CXCR7, a G-protein-coupled receptor recently identified as a scavenger receptor for the chemokine SDF-1/CXCL12. CXCR7 is highly expressed in human breast, lung, and prostate cancers. Using quantitative reverse transcription-PCR analyses, we demonstrated that CXCR7 was repressed in U2OS cells overexpressing HIC1. Inversely, inactivation of endogenous HIC1 by RNA interference in normal human WI38 fibroblasts results in up-regulation of CXCR7 and SIRT1. In silico analyses followed by deletion studies and luciferase reporter assays identified a functional and phylogenetically conserved HIC1-responsive element in the human CXCR7 promoter. Moreover, chromatin immunoprecipitation (ChIP) and ChIP upon ChIP experiments demonstrated that endogenous HIC1 proteins are bound together with the C-terminal binding protein corepressor to the CXCR7 and SIRT1 promoters in WI38 cells. Taken together, our results implicate the tumor suppressor HIC1 in the transcriptional regulation of the chemokine receptor CXCR7, a key player in the promotion of tumorigenesis in a wide variety of cell types.

Ets-1 p51 and p42 isoforms differentially modulate Stromelysin-1 promoter according to induced DNA bend orientation.

The Stromelysin-1 gene promoter contains a palindrome of two Ets-binding sites (EBS) that bind the p51 and p42 isoforms of the human Ets-1-transcription factor. A previous study established that full gene transactivation is associated with a ternary complex consisting of two p51 bound to the two EBS on the promoter. p42, only able to bind one of the two EBS, induces only very weak activity. Here, we investigate the mechanism by which the Stromelysin-1 promoter discriminates between p51 and p42. The differential stoichiometry of the two Ets-1 isoforms arises from the Stromelysin-1 EBS palindrome. The ternary complex requires the presence of two inhibitory domains flanking the DNA-binding domain and the ability to form an intramolecular autoinhibition module. Most importantly, the p51-ternary and the p42-binary complexes induce DNA curvatures with opposite orientations. These results establish that differential DNA bending, via p51 and p42 differential binding, is correlated with the Stromelysin-1 promoter activation process.

Efficient system for biotinylated recombinant Ets-1 production in Escherichia coli: a useful tool for studying interactions between Ets-1 and its partners.

Identification of Ets-1 interaction partners is critical for understanding its properties. Ets-1 DNA-binding is governed by an intramolecular mechanism called autoinhibition. Ets-1 increases its DNA-binding affinity by counteracting autoinhibition through binding either to a particular organization of Ets binding sites (EBS) in palindrome, as in the Stromelysin-1 promoter, or to EBS adjacent to DNA-binding sites of its partners by combinatorial interactions, as in the Collagenase-1 promoter. Identification of new Ets-1 interaction partners should allow the identification of new functions for this transcription factor. To this end, we fused a biotin tag to Ets-1 protein in order to copurify it and its partners by affinity. For the first time, we cloned, produced in Escherichia coli and purified a biotinylated recombinant Ets-1 protein using the T7-Impact system (New England Biolabs), adapted to induce biotinylation. Nearly 100% biotinylation was attained without altering Ets-1 properties. Biotinylated Ets-1 bound to and transactivated the Stromelysin-1 promoter the same way as native Ets-1 did. It also conserved interactions with known Ets-1 partners such as c-Jun, Erk-2 and Runx-1. In addition, streptavidin pull-down and surface plasmon resonance assays demonstrated that biotinylated Ets-1 is a useful tool for qualitative and quantitative studies of Ets-1 interaction with its partners.

Can Commercial Digital Cameras Be Used as Multispectral Sensors? A Crop Monitoring Test.

The use of consumer digital cameras or webcams to characterize and monitor different features has become prevalent in various domains, especially in environmental applications. Despite some promising results, such digital camera systems generally suffer from signal aberrations due to the on-board image processing systems and thus offer limited quantitative data acquisition capability. The objective of this study was to test a series of radiometric corrections having the potential to reduce radiometric distortions linked to camera optics and environmental conditions, and to quantify the effects of these corrections on our ability to monitor crop variables. In 2007, we conducted a five-month experiment on sugarcane trial plots using original RGB and modified RGB (Red-Edge and NIR) cameras fitted onto a light aircraft. The camera settings were kept unchanged throughout the acquisition period and the images were recorded in JPEG and RAW formats. These images were corrected to eliminate the vignetting effect, and normalized between acquisition dates. Our results suggest that 1) the use of unprocessed image data did not improve the results of image analyses; 2) vignetting had a significant effect, especially for the modified camera, and 3) normalized vegetation indices calculated with vignetting-corrected images were sufficient to correct for scene illumination conditions. These results are discussed in the light of the experimental protocol and recommendations are made for the use of these versatile systems for quantitative remote sensing of terrestrial surfaces.

Relative Radiometric Normalization and Atmospheric Correction of a SPOT 5 Time Series.

Multi-temporal images acquired at high spatial and temporal resolution are an important tool for detecting change and analyzing trends, especially in agricultural applications. However, to insure a reliable use of this kind of data, a rigorous radiometric normalization step is required. Normalization can be addressed by performing an atmospheric correction of each image in the time series. The main problem is the difficulty of obtaining an atmospheric characterization at a given acquisition date. In this paper, we investigate whether relative radiometric normalization can substitute for atmospheric correction. We develop an automatic method for relative radiometric normalization based on calculating linear regressions between unnormalized and reference images. Regressions are obtained using the reflectances of automatically selected invariant targets. We compare this method with an atmospheric correction method that uses the 6S model. The performances of both methods are compared using 18 images from of a SPOT 5 time series acquired over Reunion Island. Results obtained for a set of manually selected invariant targets show excellent agreement between the two methods in all spectral bands: values of the coefficient of determination (r²) exceed 0.960, and bias magnitude values are less than 2.65. There is also a strong correlation between normalized NDVI values of sugarcane fields (r² = 0.959). Despite a relative error of 12.66% between values, very comparable NDVI patterns are observed.

The orphan COUP-TF nuclear receptors are markers for neurogenesis from cnidarians to vertebrates.

In bilaterians, COUP-TF nuclear receptors participate in neurogenesis and/or CNS patterning. In hydra, the nervous system is formed of sensory mechanoreceptor cells (nematocytes) and neuronal cells, both lineages deriving from a common stem cell. The hydra COUP-TF gene, hyCOUP-TF, which encodes highly conserved DNA-binding and ligand-binding domains, belongs to the monophyletic COUP-TFs orphan receptor family (NR2F). In adult polyps, hyCOUP-TF is expressed in nematoblasts and a subset of neuronal cells. Comparative BrDU labeling analyses performed on cells expressing either hyCOUP-TF or the paired-like gene prdl-b showed that prdl-b expression corresponded to early stages of proliferation, while hyCOUP-TF was detected slightly later. HyCOUP-TF and prdl-b expressing cells disappeared in sf-1 mutants becoming "nerve-free". Moreover hyCOUP-TF and prdl-b expression was excluded from regions undergoing developmental processes. These data suggest that hyCOUP-TF and prdl-b belong to a genetic network that appeared together with neurogenesis during early metazoan evolution. The hyCOUP-TF protein specifically bound onto the evolutionarily conserved DR1 and DR5 response elements, and repressed transactivation induced by RAR:RXR nuclear receptors in a dose-dependent manner when expressed in mammalian cells. Hence, a cnidarian transcription factor can be active in vertebrate cells, implying that functional interactions between COUP-TF and other nuclear receptors were evolutionarily conserved.

Identification and developmental expression of the zebrafish orthologue of the tumor suppressor gene HIC1.

Hypermethylated in Cancer 1 (HIC1) is a human tumor suppressor gene located at chromosome 17p13.3 which is frequently hypermethylated and transcriptionally silent in many types of tumors. In addition, its location in the Miller-Dieker syndrome's (MDS) deletion region, its embryonic expression pattern in mice and the phenotype of the HIC1-deficient mice have provided strong evidence for its implication in this contiguous-gene syndrome. HIC1 encodes a five C2H2-type zinc finger transcriptional repressor belonging to the BTB/POZ family. We have isolated the true zebrafish orthologue of human HIC1 since it has a comparable intron-exon structure and since its predicted gene product, ZfHIC1 displays much higher sequence similarities in its overall sequence (737 residues) with human HIC1 (714 residues) than the 454 residues encoded by the only zebrafish HIC1 sequence (AF111712) described so far, which has been renamed ZfHIC1alpha. Notably, the C-terminal end and one zinc finger in the DNA-binding domain are missing in ZfHIC1alpha. As a consequence, ZfHIC1 proteins bind the human HIC1 consensus DNA-binding sequence in vitro, whereas ZfHIC1alpha cannot. Analyses of the expression pattern of ZfHIC1 and of its paralogue ZfHRG22 (HIC1 related gene on chromosome 22) show that they share expression domains with their respective orthologous vertebrate genes. ZfHRG22 is prominently expressed in the brain and in neural tissues. Interestingly, the predominant expression of ZfHIC1 in the mesenchyme of the head, around the nose and the eye and in the branchial arches is possibly consistent with some of the abnormalities seen in the HIC1-deficient mice and provides another clue for the implication of HIC1 in MDS.

VE-statin, an endothelial repressor of smooth muscle cell migration.

The recruitment and proliferation of smooth muscle cells and pericytes are two key events for the stabilization of newly formed capillaries during angiogenesis and, when out of control in the adult, are the main causes of arteriosclerosis. We have identified a novel gene, named VE-statin for vascular endothelial-statin, which is expressed specifically by endothelial cells of the developing mouse embryo and in the adult, and in early endothelial progenitors. The mouse and human VE-statin genes have been located on chromosome 2 and 9, respectively, they span >10 kbp and are transcribed in two major variants arising from independent initiation sites. The VE-statin transcripts code for a unique protein of 30 kDa that contains a signal peptide and two epidermal growth factor (EGF)-like modules. VE-statin is found in the cellular endoplasmic reticulum and secreted in the cell supernatant. Secreted VE-statin inhibits platelet-derived growth factor (PDGF)-BB-induced smooth muscle cell migration, but has no effects on endothelial cell migration. VE-statin is the first identified inhibitor of mural cell migration specifically produced by endothelial cells.

Genomic organization and expression of the mouse Brca2 gene.

A mutation of the Brca2 gene product is responsible for a large proportion of the inherited breast cancers. Here, we have demonstrated that the mouse Brca2 gene is composed of 27 exons and 26 introns, spanning approximately 48 kbp, almost all intron-exon junctions being classical. The overall mouse Brca2 gene structure is highly similar in the coding sequences to that of the human gene. The predicted 11-kb transcript is predominantly present in testis, spleen, thymus, epididymis, and seminal vesicles. A smaller-size, strong positive hybridization signal, which was obtained by using 5' end exons as probes, is ubiquitously observed in mouse tissues. The exact origin and function of this small transcript is currently unknown. The transcription start site of this gene has been identified at approximately 300 bp upstream from the translation initiation codon, and the first 148 bp proximal TATA-less promoter region is sufficient to activate maximal transcription of this gene in mammary cells.

ETS-1 transcription factor binds cooperatively to the palindromic head to head ETS-binding sites of the stromelysin-1 promoter by counteracting autoinhibition.

Stromelysin-1 (matrix metalloproteinase-3) is a member of the matrix metalloproteinase family. Regulation of its gene expression is critical for tissue homeostasis. Patterns of increased co-expression of stromelysin-1 and ETS-1 genes have been observed in pathological processes. Stromelysin-1 promoter is transactivated by ETS proteins through two palindromic head to head ETS-binding sites, an unusual configuration among metalloproteinase promoters. By using surface plasmon resonance, electrophoretic mobility shift assay, and photo-cross-linking, we showed that full-length human ETS-1 (p51) binds cooperatively to the ETS-binding site palindrome of the human stromelysin-1 promoter, with facilitated binding of the second ETS-1 molecule to form an ETS-1.DNA.ETS-1 ternary complex. The study of N-terminal deletion mutants allowed us to conclude that cooperative binding implied autoinhibition counteraction, requiring the 245-330-residue region of the protein that is encoded by exon VII of the gene. This region was deleted in the natural p42 isoform of ETS-1, which was unable to bind cooperatively to the palindrome. Transient transfection experiments showed a good correlation between DNA binding and promoter transactivation for p51. In contrast, p42 showed a poorer transactivation, reinforcing the significance of cooperative binding for full transactivation. It is the first time that ETS-1 was shown to be able to counteract its own autoinhibition.