title: Detection of genome-wide polymorphisms in the AT-rich Plasmodium falciparum genome using a high-density microarray.
abstract: BACKGROUND
  Genetic mapping is a powerful method to identify mutations that cause drug resistance and other phenotypic changes in the human malaria parasite Plasmodium falciparum. For efficient mapping of a target gene, it is often necessary to genotype a large number of polymorphic markers. Currently, a community effort is underway to collect single nucleotide polymorphisms (SNP) from the parasite genome. Here we evaluate polymorphism detection accuracy of a high-density 'tiling' microarray with 2.56 million probes by comparing single feature polymorphisms (SFP) calls from the microarray with known SNP among parasite isolates.
  
  
  RESULTS
  We found that probe GC content, SNP position in a probe, probe coverage, and signal ratio cutoff values were important factors for accurate detection of SFP in the parasite genome. We established a set of SFP calling parameters that could predict mSFP (SFP called by multiple overlapping probes) with high accuracy (> or = 94%) and identified 121,087 mSFP genome-wide from five parasite isolates including 40,354 unique mSFP (excluding those from multi-gene families) and approximately 18,000 new mSFP, producing a genetic map with an average of one unique mSFP per 570 bp. Genomic copy number variation (CNV) among the parasites was also cataloged and compared.
  
  
  CONCLUSIONS
  A large number of mSFP were discovered from the P. falciparum genome using a high-density microarray, most of which were in clusters of highly polymorphic genes at chromosome ends. Our method for accurate mSFP detection and the mSFP identified will greatly facilitate large-scale studies of genome variation in the P. falciparum parasite and provide useful resources for mapping important parasite traits.
authors: Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Bethesda, MD 20892, USA. hojiang@niaid.nih.gov
authors: Hongying
authors: H
authors: Jiang
authors: Ming
authors: M
authors: Yi
authors: Jianbing
authors: J
authors: Mu
authors: Louie
authors: L
authors: Zhang
authors: Al
authors: A
authors: Ivens
authors: Leszek J
authors: LJ
authors: Klimczak
authors: Yentram
authors: Y
authors: Huyen
authors: Robert M
authors: RM
authors: Stephens
authors: Xin-Zhuan
authors: XZ
authors: Su
mesh_terms: D000818:Animals; D001482:Base Composition; D002874:Chromosome Mapping; D019295:Computational Biology; D015342:DNA Probes; D016054:DNA, Protozoan / Q000235:genetics; D018628:Gene Dosage; D014644:Genetic Variation; D018503:Genome, Protozoan; D020411:Oligonucleotide Array Sequence Analysis / Q000379:methods*; D010963:Plasmodium falciparum / Q000235:genetics*; D020641:Polymorphism, Single Nucleotide; D012372:ROC Curve; D012680:Sensitivity and Specificity; D017422:Sequence Analysis, DNA
chemical_list: D015342:DNA Probes; D016054:DNA, Protozoan