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1.  Unveiling of the Diversity of Prasinoviruses (Phycodnaviridae) in Marine Samples by Using High-Throughput Sequencing Analyses of PCR-Amplified DNA Polymerase and Major Capsid Protein Genes 
Applied and Environmental Microbiology  2014;80(10):3150-3160.
Viruses strongly influence the ecology and evolution of their eukaryotic hosts in the marine environment, but little is known about their diversity and distribution. Prasinoviruses infect an abundant and widespread class of phytoplankton, the Mamiellophyceae, and thereby exert a specific and important role in microbial ecosystems. However, molecular tools to specifically identify this viral genus in environmental samples are still lacking. We developed two primer sets, designed for use with polymerase chain reactions and 454 pyrosequencing technologies, to target two conserved genes, encoding the DNA polymerase (PolB gene) and the major capsid protein (MCP gene). While only one copy of the PolB gene is present in Prasinovirus genomes, there are at least seven paralogs for MCP, the copy we named number 6 being shared with other eukaryotic alga-infecting viruses. Primer sets for PolB and MCP6 were thus designed and tested on 6 samples from the Tara Oceans project. The results suggest that the MCP6 amplicons show greater richness but that PolB gave a wider coverage of Prasinovirus diversity. As a consequence, we recommend use of the PolB primer set, which will certainly reveal exciting new insights about the diversity and distribution of prasinoviruses at the community scale.
PMCID: PMC4018913  PMID: 24632251
2.  Exploring nucleo-cytoplasmic large DNA viruses in Tara Oceans microbial metagenomes 
The ISME Journal  2013;7(9):1678-1695.
Nucleo-cytoplasmic large DNA viruses (NCLDVs) constitute a group of eukaryotic viruses that can have crucial ecological roles in the sea by accelerating the turnover of their unicellular hosts or by causing diseases in animals. To better characterize the diversity, abundance and biogeography of marine NCLDVs, we analyzed 17 metagenomes derived from microbial samples (0.2–1.6 μm size range) collected during the Tara Oceans Expedition. The sample set includes ecosystems under-represented in previous studies, such as the Arabian Sea oxygen minimum zone (OMZ) and Indian Ocean lagoons. By combining computationally derived relative abundance and direct prokaryote cell counts, the abundance of NCLDVs was found to be in the order of 104–105 genomes ml−1 for the samples from the photic zone and 102–103 genomes ml−1 for the OMZ. The Megaviridae and Phycodnaviridae dominated the NCLDV populations in the metagenomes, although most of the reads classified in these families showed large divergence from known viral genomes. Our taxon co-occurrence analysis revealed a potential association between viruses of the Megaviridae family and eukaryotes related to oomycetes. In support of this predicted association, we identified six cases of lateral gene transfer between Megaviridae and oomycetes. Our results suggest that marine NCLDVs probably outnumber eukaryotic organisms in the photic layer (per given water mass) and that metagenomic sequence analyses promise to shed new light on the biodiversity of marine viruses and their interactions with potential hosts.
PMCID: PMC3749498  PMID: 23575371
eukaryotic viruses; marine NCLDVs; taxon co-occurrence; oomycetes
3.  A Holistic Approach to Marine Eco-Systems Biology 
PLoS Biology  2011;9(10):e1001177.
The structure, robustness, and dynamics of ocean plankton ecosystems remain poorly understood due to sampling, analysis, and computational limitations. The Tara Oceans consortium organizes expeditions to help fill this gap at the global level.
PMCID: PMC3196472  PMID: 22028628
4.  Metagenome Annotation Using a Distributed Grid of Undergraduate Students 
PLoS Biology  2008;6(11):e296.
The Annotathon is a novel bioinformatics teaching environment, where undergraduate students join in a community annotation effort. Besides being a rewarding educational tool, it holds the added promise of potentially useful scientific findings.
PMCID: PMC2586363  PMID: 19067492
5.  MicroArray Facility: a laboratory information management system with extended support for Nylon based technologies 
BMC Genomics  2006;7:240.
High throughput gene expression profiling (GEP) is becoming a routine technique in life science laboratories. With experimental designs that repeatedly span thousands of genes and hundreds of samples, relying on a dedicated database infrastructure is no longer an option.
GEP technology is a fast moving target, with new approaches constantly broadening the field diversity. This technology heterogeneity, compounded by the informatics complexity of GEP databases, means that software developments have so far focused on mainstream techniques, leaving less typical yet established techniques such as Nylon microarrays at best partially supported.
MAF (MicroArray Facility) is the laboratory database system we have developed for managing the design, production and hybridization of spotted microarrays. Although it can support the widely used glass microarrays and oligo-chips, MAF was designed with the specific idiosyncrasies of Nylon based microarrays in mind. Notably single channel radioactive probes, microarray stripping and reuse, vector control hybridizations and spike-in controls are all natively supported by the software suite. MicroArray Facility is MIAME supportive and dynamically provides feedback on missing annotations to help users estimate effective MIAME compliance. Genomic data such as clone identifiers and gene symbols are also directly annotated by MAF software using standard public resources. The MAGE-ML data format is implemented for full data export. Journalized database operations (audit tracking), data anonymization, material traceability and user/project level confidentiality policies are also managed by MAF.
MicroArray Facility is a complete data management system for microarray producers and end-users. Particular care has been devoted to adequately model Nylon based microarrays. The MAF system, developed and implemented in both private and academic environments, has proved a robust solution for shared facilities and industry service providers alike.
PMCID: PMC1592093  PMID: 16987406
7.  Mice Lacking the UBC4-testis Gene Have a Delay in Postnatal Testis Development but Normal Spermatogenesis and Fertility 
Molecular and Cellular Biology  2005;25(15):6346-6354.
Activation of ubiquitination occurs during spermatogenesis and is dependent on the induction of isoforms of the UBC4 family of ubiquitin-conjugating enzymes. The UBC4-testis isoform is testis specific, is induced in round spermatids, and demonstrates biochemical functions distinct from a ubiquitously expressed isoform UBC4-1. To explore further the function of UBC4-testis, mice bearing inactivation of this gene were produced. Homozygous (−/−) mice showed normal body growth and fertility. Although testis weight and morphology were normal in testes from adult mice, examination of young mice during the first wave of spermatogenesis revealed that testes were ∼10% smaller in weight at 40 and 45 days of age but had become normal at 65 days of age. Overall protein content, levels of ubiquitinated proteins, and ubiquitin-conjugating activity did not differ between wild-type and homozygous (−/−) mice. Spermatid number, as well as the motility of spermatozoa isolated from the epididymis, was also normal in homozygous (−/−) mice. To determine whether the germ cells lacking UBC4-testis might be more sensitive to stress, testes from wild-type and knockout mice were exposed to heat stress by implantation in the abdominal cavity. Testes from both strains of mice showed similar rates of degeneration in response to heat. The lack of an obvious phenotype did not appear to be due to induction of other UBC4 isoforms, as shown by two-dimensional gel immunoblotting. Our data indicate that UBC4-testis plays a role in early maturation of the testis and suggest that the many UBC4 isoforms have mixed redundant and specific functions.
PMCID: PMC1190331  PMID: 16024774
9.  DNA microarray data and contextual analysis of correlation graphs 
BMC Bioinformatics  2003;4:15.
DNA microarrays are used to produce large sets of expression measurements from which specific biological information is sought. Their analysis requires efficient and reliable algorithms for dimensional reduction, classification and annotation.
We study networks of co-expressed genes obtained from DNA microarray experiments. The mathematical concept of curvature on graphs is used to group genes or samples into clusters to which relevant gene or sample annotations are automatically assigned. Application to publicly available yeast and human lymphoma data demonstrates the reliability of the method in spite of its simplicity, especially with respect to the small number of parameters involved.
We provide a method for automatically determining relevant gene clusters among the many genes monitored with microarrays. The automatic annotations and the graphical interface improve the readability of the data. A C++ implementation, called Trixy, is available from .
PMCID: PMC156617  PMID: 12720549
11.  Divergent N-Terminal Sequences Target an Inducible Testis Deubiquitinating Enzyme to Distinct Subcellular Structures 
Molecular and Cellular Biology  2000;20(17):6568-6578.
Ubiquitin-specific processing proteases (UBPs) presently form the largest enzyme family in the ubiquitin system, characterized by a core region containing conserved motifs surrounded by divergent sequences, most commonly at the N-terminal end. The functions of these divergent sequences remain unclear. We identified two isoforms of a novel testis-specific UBP, UBP-t1 and UBP-t2, which contain identical core regions but distinct N termini, thereby permitting dissection of the functions of these two regions. Both isoforms were germ cell specific and developmentally regulated. Immunocytochemistry revealed that UBP-t1 was induced in step 16 to 19 spermatids while UBP-t2 was expressed in step 18 to 19 spermatids. Immunoelectron microscopy showed that UBP-t1 was found in the nucleus while UBP-t2 was extranuclear and was found in residual bodies. For the first time, we show that the differential subcellular localization was due to the distinct N-terminal sequences. When transfected into COS-7 cells, the core region was expressed throughout the cell but the UBP-t1 and UBP-t2 isoforms were concentrated in the nucleus and the perinuclear region, respectively. Fusions of each N-terminal end with green fluorescent protein yielded the same subcellular localization as the native proteins, indicating that the N-terminal ends were sufficient for determining differential localization. Interestingly, UBP-t2 colocalized with anti-γ-tubulin immunoreactivity, indicating that like several other components of the ubiquitin system, a deubiquitinating enzyme is associated with the centrosome. Regulated expression and alternative N termini can confer specificity of UBP function by restricting its temporal and spatial loci of action.
PMCID: PMC86134  PMID: 10938131
12.  The EMBL Nucleotide Sequence Database 
Nucleic Acids Research  2000;28(1):19-23.
The European Molecular Biology Laboratory (EMBL) Nucleotide Sequence Database ( uk/embl/index.html ) is maintained at the European Bioinformatics Institute (EBI) in an international collaboration with the DNA Data Bank of Japan (DDBJ) and GenBank (USA). Data is exchanged amongst the collaborative databases on a daily basis. The major contributors to the EMBL database are individual authors and genome project groups. WEBIN is the preferred web-based submission system for individual submitters, whilst automatic procedures allow incorporation of sequence data from large-scale genome sequencing centres and from the European Patent Office (EPO). Database releases are produced quarterly. Network services allow free access to the most up-to-date data collection via Internet and WWW interfaces. EBI’s Sequence Retrieval System (SRS) is a network browser for databanks in molecular biology, integrating and linking the main nucleotide and protein databases plus many specialised databases. For sequence similarity searching a variety of tools (e.g., BLITZ, FASTA, BLAST) are available which allow external users to compare their own sequences against the most currently available data in the EMBL Nucleotide Sequence Database and SWISS-PROT.
PMCID: PMC102461  PMID: 10592171
13.  Submission of Microarray Data to Public Repositories 
PLoS Biology  2004;2(9):e317.
The Microarray Gene Expression Data Society believe that the time is right for journals to require that microarray data be deposited in public repositories, as a condition for publication
PMCID: PMC514887  PMID: 15340489

Results 1-13 (13)