PO 8249 SUBMICROSCOPIC PLASMODIUM FALCIPARUM INFECTIONS IN MATCHED PERIPHERAL, PLACENTAL AND UMBILICAL CORD BLOOD SAMPLES FROM CONGOLESE WOMEN AT DELIVERY

Background

This cross-sectional study was conducted to characterise P. falciparum infections matched in peripheral, placental and cord blood among Congolese women at delivery receiving 1, 2 or more doses of sulfadoxine-pyrimethamine. The cross-sectional study was conducted in a Southern district of Brazzaville, Republic of the Congo, between March 2014 and April 2015.

Methods

Peripheral and placental blood samples were collected for P. falciparum infection investigation by microscopy and nested polymerase chain reaction (PCR), using P. falciparum merozoite surface protein-2 (msp2) gene as marker.

Results

Of the 370 pregnant women recruited, only 7.3% peripheral and 2.7% placental blood samples were found smear-positive for P. falciparum by microscopy. All isolates from cord blood were microscopy-negative. However, the prevalences of submicroscopic P. falciparum infections (detectable only by PCR) were 25.4%, 16.7% and 9.4% in peripheral, placental and cord blood respectively. The frequency of 3D7 msp2 alleles was the highest (>60%) whatever the blood considered. We found a high prevalence of submicroscopic infection in pregnant women associated with a high genetic diversity of P. falciparum isolates. The multiplicity of infection ranged between 1.2 and 1.4 irrespective of the blood compartment, and it showed no significant association with maternal age (p=0.3), gravidity (p=0.1) or sulfadoxine-pyrimethamine (p=0.3).

Conclusion

In summary, this study showed that there is a high prevalence of submicroscopic infection and a high genetic diversity of Plasmodium falciparum strains in Congo. This diversity varies according to maternal, placental and umbilical cord blood. Age, gravidity and doses of preventive treatment based on sulfadoxine-pyrimethamine do not interfere with the multiplicity of infections.

Abstract 478: Predicting interactome networks perturbations in human cancer: application to gene fusions in acute lymphoblastic leukemia

Genomic variations such point mutations and gene fusions are directly or indirectly associated with human diseases. They are recognized as diagnostic, prognostic markers and as therapeutic targets. However, predicting the functional impact of these genetic alterations beyond affected genes and their products is challenging because diseased phenotypes likely result in complex molecular interaction networks. Using as models three different chromosomal translocations ETV6-RUNX1 (TEL-AML1), BCR-ABL1, and E2A-PBX1 (TCF3-PBX1) frequently found in B-cell acute lymphoblastic leukemia (B-ALL), we develop an approach to extract from gene expression changes, perturbed molecular interactions. We show that the Myc and JunD transcriptional circuits are specifically deregulated following TEL-AML1 and TCF3-PBX1 gene fusions, respectively. We also identified the bulk mRNA NXF1-dependent machinery as a direct target for the TCF3-PBX1 fusion protein. Through a novel approach combining gene expression and interactome data analysis, we provide new insight into TCF3-PBX1 and TEL-AML1 acute lymphoblastic leukemia.

Note: This abstract was not presented at the meeting.

Citation Format: Leon Hajingabo, Sarah Daakour, Maud Martin, Reinhard Grausenburger, Renate Panzer-Grümayer, Franck Dequiedt, Jacques Van Helden, Jean-Claude Twizere, Nicolas Simonis. Predicting interactome networks perturbations in human cancer: application to gene fusions in acute lymphoblastic leukemia. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 478. doi:10.1158/1538-7445.AM2014-478

Clusters of conserved beta cell marker genes for assessment of beta cell phenotype

Background and Methodology

The aim of this study was to establish a gene expression blueprint of pancreatic beta cells conserved from rodents to humans and to evaluate its applicability to assess shifts in the beta cell differentiated state. Genome-wide mRNA expression profiles of isolated beta cells were compared to those of a large panel of other tissue and cell types, and transcripts with beta cell-abundant and -selective expression were identified. Iteration of this analysis in mouse, rat and human tissues generated a panel of conserved beta cell biomarkers. This panel was then used to compare isolated versus laser capture microdissected beta cells, monitor adaptations of the beta cell phenotype to fasting, and retrieve possible conserved transcriptional regulators.

Principal Findings

A panel of 332 conserved beta cell biomarker genes was found to discriminate both isolated and laser capture microdissected beta cells from all other examined cell types. Of all conserved beta cell-markers, 15% were strongly beta cell-selective and functionally associated to hormone processing, 15% were shared with neuronal cells and associated to regulated synaptic vesicle transport and 30% with immune plus gut mucosal tissues reflecting active protein synthesis. Fasting specifically down-regulated the latter cluster, but preserved the neuronal and strongly beta cell-selective traits, indicating preserved differentiated state. Analysis of consensus binding site enrichment indicated major roles of CREB/ATF and various nutrient- or redox-regulated transcription factors in maintenance of differentiated beta cell phenotype.

Conclusions

Conserved beta cell marker genes contain major gene clusters defined by their beta cell selectivity or by their additional abundance in either neural cells or in immune plus gut mucosal cells. This panel can be used as a template to identify changes in the differentiated state of beta cells.

Prophinder: a computational tool for prophage prediction in prokaryotic genomes

Prophinder is a prophage prediction tool coupled with a prediction database, a web server and web service. Predicted prophages will help to fill the gaps in the current sparse phage sequence space, which should cover an estimated 100 million species. Systematic and reliable predictions will enable further studies of prophages contribution to the bacteriophage gene pool and to better understand gene shuffling between prophages and phages infecting the same host.

AVAILABILITY

Softare is available at http://aclame.ulb.ac.be/prophinder

Reticulate representation of evolutionary and functional relationships between phage genomes

Bacteriophage genomes show pervasive mosaicism, indicating the importance of horizontal gene exchange in their evolution. Phage genomes represent unique combinations of modules, each of them with a different phylogenetic history. The traditional classification, based on a variety of criteria such as nucleic acid type (single/double-stranded DNA/RNA), morphology, and host range, appeared inconsistent with sequence analyses. With the genomic era, an ever increasing number of sequenced phages cannot be classified, in part due to a lack of morphological information and in part to the intrinsic incapability of tree-based methods to efficiently deal with mosaicism. This problem led some virologists to call for a moratorium on the creation of additional taxa in the order Caudovirales, in order to let virologists discuss classification schemes that might better suit phage evolution. In this context, we propose a framework for a reticulate classification of phages based on gene content. Starting from gene families, we built a weighted graph, where nodes represent phages and edges represent phage-phage similarities in terms of shared genes. We then apply various measures of graph topology to analyze the resulting graph. Most double-stranded DNA phages are found in a single component. The values of the clustering coefficient and closeness distinguish temperate from virulent phages, whereas chimeric phages are characterized by a high betweenness coefficient. We apply a 2-step clustering method to this graph to generate a reticulate classification of phages: Each phage is associated with a membership vector, which quantitatively characterizes its membership to the set of clusters. Furthermore, we cluster genes based on their "phylogenetic profiles" to define "evolutionary cohesive modules." In virulent phages, evolutionary modules span several functional categories, whereas in temperate phages they correspond better to functional modules. Moreover, despite the fact that modules only cover a fraction of all phage genes, phage groups can be distinguished by their different combination of modules, serving the bases for a higher level reticulate classification. These 2 classification schemes provide an automatic and dynamic way of representing the relationships within the phage population and can be extended to include newly sequenced phage genomes, as well as other types of genetic elements.

Molecular evolution of eukaryotic genomes: hemiascomycetous yeast spliceosomal introns

As part of the exploratory sequencing program Génolevures, visual scrutinisation and bioinformatic tools were used to detect spliceosomal introns in seven hemiascomycetous yeast species. A total of 153 putative novel introns were identified. Introns are rare in yeast nuclear genes (<5% have an intron), mainly located at the 5' end of ORFs, and not highly conserved in sequence. They all share a clear non-random vocabulary: conserved splice sites and conserved nucleotide contexts around splice sites. Homologues of metazoan snRNAs and putative homologues of SR splicing factors were identified, confirming that the spliceosomal machinery is highly conserved in eukaryotes. Several introns' features were tested as possible markers for phylogenetic analysis. We found that intron sizes vary widely within each genome, and according to the phylogenetic position of the yeast species. The evolutionary origin of spliceosomal introns was examined by analysing the degree of conservation of intron positions in homologous yeast genes. Most introns appeared to exist in the last common ancestor of present day yeast species, and then to have been differentially lost during speciation. However, in some cases, it is difficult to exclude a possible sliding event affecting a pre-existing intron or a gain of a novel intron. Taken together, our results indicate that the origin of spliceosomal introns is complex within a given genome, and that present day introns may have resulted from a dynamic flux between intron conservation, intron loss and intron gain during the evolution of hemiascomycetous yeasts.