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Open Access Highly Accessed Research article

A novel multifunctional oligonucleotide microarray for Toxoplasma gondii

Amit Bahl1, Paul H Davis2, Michael Behnke37, Florence Dzierszinski4, Manjunatha Jagalur5, Feng Chen6, Dhanasekaran Shanmugam6, Michael W White38, David Kulp5 and David S Roos6*

Author Affiliations

1 Genomics and Computational Biology, University of Pennsylvania, Philadelphia PA 19104, USA

2 Department of Biology, University of Nebraska at Omaha, Omaha NE 68182

3 Department of Veterinary Molecular Biology, Montana State University, Bozeman MT, 59717, USA

4 Institute of Parasitology, McGill University, Ste. Anne de Bellevue, Quebec H9X 3V9, Canada

5 Department of Computer Science, University of Massachusetts, Amherst MA, 01003, USA

6 Department of Biology, University of Pennsylvania, Philadelphia PA 19104, USA

7 Department of Molecular Microbiology, Washington University School of Medicine, St. Louis MO, 63130, USA

8 Department of Molecular Medicine, University of South Florida, Tampa FL, 33620, USA

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BMC Genomics 2010, 11:603  doi:10.1186/1471-2164-11-603

Published: 25 October 2010

Abstract

Background

Microarrays are invaluable tools for genome interrogation, SNP detection, and expression analysis, among other applications. Such broad capabilities would be of value to many pathogen research communities, although the development and use of genome-scale microarrays is often a costly undertaking. Therefore, effective methods for reducing unnecessary probes while maintaining or expanding functionality would be relevant to many investigators.

Results

Taking advantage of available genome sequences and annotation for Toxoplasma gondii (a pathogenic parasite responsible for illness in immunocompromised individuals) and Plasmodium falciparum (a related parasite responsible for severe human malaria), we designed a single oligonucleotide microarray capable of supporting a wide range of applications at relatively low cost, including genome-wide expression profiling for Toxoplasma, and single-nucleotide polymorphism (SNP)-based genotyping of both T. gondii and P. falciparum. Expression profiling of the three clonotypic lineages dominating T. gondii populations in North America and Europe provides a first comprehensive view of the parasite transcriptome, revealing that ~49% of all annotated genes are expressed in parasite tachyzoites (the acutely lytic stage responsible for pathogenesis) and 26% of genes are differentially expressed among strains. A novel design utilizing few probes provided high confidence genotyping, used here to resolve recombination points in the clonal progeny of sexual crosses. Recent sequencing of additional T. gondii isolates identifies >620 K new SNPs, including ~11 K that intersect with expression profiling probes, yielding additional markers for genotyping studies, and further validating the utility of a combined expression profiling/genotyping array design. Additional applications facilitating SNP and transcript discovery, alternative statistical methods for quantifying gene expression, etc. are also pursued at pilot scale to inform future array designs.

Conclusions

In addition to providing an initial global view of the T. gondii transcriptome across major lineages and permitting detailed resolution of recombination points in a historical sexual cross, the multifunctional nature of this array also allowed opportunities to exploit probes for purposes beyond their intended use, enhancing analyses. This array is in widespread use by the T. gondii research community, and several aspects of the design strategy are likely to be useful for other pathogens.