title: Reduced heterozygosity at intragenic and flanking microsatellites of pfcrt gene establishes natural selection based molecular evolution of chloroquine-resistant Plasmodium falciparum in India.
abstract: The positive selection of a nucleotide substitution in exon 2 of Plasmodium falciparum chloroquine resistance transporter (pfcrt) gene (mutation responsible for chloroquine resistance) causes a reduction in variation of neutral loci close to the gene. This reduction in allelic diversity around flanking regions of pfcrt gene was reported in worldwide chloroquine resistant isolates and referred as selective sweep. In Plasmodium falciparum isolates of India, the selective sweep in flanking loci of pfcrt gene is well established, however, high allelic diversity observed in intragenic microsatellites of pfcrt gene implied an ongoing genetic recombination. To understand, if molecular evolution of chloroquine-resistant P. falciparum isolates in India follow a selective sweep model, we analyzed genetic diversity at both seven intragenic and seven flanking microsatellites of pfcrt (-24 to +106kb) gene in chloroquine sensitive and resistant parasites originating from high and low transmission areas. We observed low expected heterozygosity at all loci of resistant pfcrt-haplotypes (He=0-0.77) compared to the wild-type (He=0.38-0.96). Resistant SVMNT from high transmission areas showed significantly higher mean He (P=0.03, t-test) at both intragenic and pfcrt-flanking loci (-24 to +22 kb) in comparison to low transmission areas. Our observation of reduction in variation at both intragenic and flanking loci of mutant pfcrt gene confirmed the selective sweep model of natural selection in chloroquine resistant P. falciparum isolates in India.
authors.affiliation: National Institute of Malaria Research, Indian Council of Medical Research, Dwarka Sector-8, New Delhi 110077, India.
authors.forename: Prashant K
authors.initials: PK
authors.lastname: Mallick
authors.forename: Ruchi
authors.initials: R
authors.lastname: Singh
authors.forename: Om P
authors.initials: OP
authors.lastname: Singh
authors.forename: Ashok K
authors.initials: AK
authors.lastname: Singh
authors.forename: Virendra K
authors.initials: VK
authors.lastname: Bhasin
authors.forename: Neena
authors.initials: N
authors.lastname: Valecha
mesh_terms: D000962:Antimalarials / Q000494:pharmacology*; D002738:Chloroquine / Q000494:pharmacology*; D016054:DNA, Protozoan / Q000235:genetics; D004351:Drug Resistance / Q000235:genetics*; D019143:Evolution, Molecular; D014644:Genetic Variation; D006239:Haplotypes / Q000235:genetics; D006801:Humans; D007194:India; D015810:Linkage Disequilibrium / Q000235:genetics; D016778:Malaria, Falciparum / Q000188:drug therapy* / Q000469:parasitology; D026901:Membrane Transport Proteins / Q000235:genetics*; D018895:Microsatellite Repeats / Q000235:genetics; D010963:Plasmodium falciparum / Q000187:drug effects* / Q000235:genetics* / Q000302:isolation & purification; D015800:Protozoan Proteins / Q000235:genetics*; D012641:Selection, Genetic
chemical_list: D000962:Antimalarials; D016054:DNA, Protozoan; D026901:Membrane Transport Proteins; C416369:PfCRT protein, Plasmodium falciparum; D015800:Protozoan Proteins; D002738:Chloroquine
keywords: Chloroquine resistance; Heterozygosity; India; Microsatellite; Plasmodium falciparum; pfcrt gene