title: Little Polymorphism at the K13 Propeller Locus in Worldwide Plasmodium falciparum Populations Prior to the Introduction of Artemisinin Combination Therapies.
abstract: The emergence and spread of artemisinin-resistant Plasmodium falciparum is of huge concern for the global effort toward malaria control and elimination. Artemisinin resistance, defined as a delayed time to parasite clearance following administration of artemisinin, is associated with mutations in the Pfkelch13 gene of resistant parasites. To date, as many as 60 nonsynonymous mutations have been identified in this gene, but whether these mutations have been selected by artemisinin usage or merely reflect natural polymorphism independent of selection is currently unknown. To clarify this, we sequenced the Pfkelch13 propeller domain in 581 isolates collected before (420 isolates) and after (161 isolates) the implementation of artemisinin combination therapies (ACTs), from various regions of endemicity worldwide. Nonsynonymous mutations were observed in 1% of parasites isolated prior to the introduction of ACTs. Frequencies of mutant isolates, nucleotide diversity, and haplotype diversity were significantly higher in the parasites isolated from populations exposed to artemisinin than in those from populations that had not been exposed to the drug. In the artemisinin-exposed population, a significant excess of dN compared to dS was observed, suggesting the presence of positive selection. In contrast, pairwise comparison of dN and dS and the McDonald and Kreitman test indicate that purifying selection acts on the Pfkelch13 propeller domain in populations not exposed to ACTs. These population genetic analyses reveal a low baseline of Pfkelch13 polymorphism, probably due to purifying selection in the absence of artemisinin selection. In contrast, various Pfkelch13 mutations have been selected under artemisinin pressure.
authors.affiliation: Department of Molecular and Cellular Parasitology, Juntendo University School of Medicine, Tokyo, Japan Department of International Affairs and Tropical Medicine, Tokyo Women's Medical University, Tokyo, Japan tmita@juntendo.ac.jp.
authors.forename: Toshihiro
authors.initials: T
authors.lastname: Mita
authors.affiliation: Malaria Unit, Department of Pathology, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan.
authors.forename: Richard
authors.initials: R
authors.lastname: Culleton
authors.affiliation: Department of International Affairs and Tropical Medicine, Tokyo Women's Medical University, Tokyo, Japan.
authors.forename: Nobuyuki
authors.initials: N
authors.lastname: Takahashi
authors.affiliation: Department of Tropical Medicine and Parasitology, Dokkyo Medical University, Tochigi, Japan.
authors.forename: Masatoshi
authors.initials: M
authors.lastname: Nakamura
authors.affiliation: Department of International Affairs and Tropical Medicine, Tokyo Women's Medical University, Tokyo, Japan.
authors.forename: Takahiro
authors.initials: T
authors.lastname: Tsukahara
authors.affiliation: Malaria Unit, Department of Pathology, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan Centre for Research in Therapeutic Sciences, Strathmore University, Nairobi, Kenya South Eastern Kenya University, Kitui, Kenya.
authors.forename: Carol W
authors.initials: CW
authors.lastname: Hunja
authors.affiliation: Department of Molecular and Cellular Parasitology, Juntendo University School of Medicine, Tokyo, Japan Department of Biomedical Chemistry, Graduate School of Medicine, The University of Tokyo, Tokyo, Japan.
authors.forename: Zin Zayar
authors.initials: ZZ
authors.lastname: Win
authors.affiliation: Department of Microbiology, The University of Medicine 1, Yangon, Myanmar.
authors.forename: Wah Win
authors.initials: WW
authors.lastname: Htike
authors.affiliation: Department of International Affairs and Tropical Medicine, Tokyo Women's Medical University, Tokyo, Japan.
authors.forename: Aung S
authors.initials: AS
authors.lastname: Marma
authors.affiliation: Department of International Affairs and Tropical Medicine, Tokyo Women's Medical University, Tokyo, Japan.
authors.forename: Lek
authors.initials: L
authors.lastname: Dysoley
authors.affiliation: Laboratoire de Pharmacologie, Centre d'Etudes sur les Ressources Vegetales, Brazzaville, Republic of Congo.
authors.forename: Mathieu
authors.initials: M
authors.lastname: Ndounga
authors.affiliation: Department of International Affairs and Tropical Medicine, Tokyo Women's Medical University, Tokyo, Japan.
authors.forename: Mawuli
authors.initials: M
authors.lastname: Dzodzomenyo
authors.affiliation: Department of International Affairs and Tropical Medicine, Tokyo Women's Medical University, Tokyo, Japan.
authors.forename: Willis S
authors.initials: WS
authors.lastname: Akhwale
authors.affiliation: Department of Global Health, School of Health Sciences, University of the Ryukyus, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Kobayashi
authors.affiliation: Department of Protozoology, Institute of Tropical Medicine, Nagasaki University, Nagasaki, Japan.
authors.forename: Haruki
authors.initials: H
authors.lastname: Uemura
authors.affiliation: Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden Department of Parasitology, Osaka City University Graduate School of Medicine, Osaka, Japan.
authors.forename: Akira
authors.initials: A
authors.lastname: Kaneko
authors.affiliation: Centre for Health Research and Diagnostics, Divine Word University, Madang, Papua New Guinea.
authors.forename: Francis
authors.initials: F
authors.lastname: Hombhanje
authors.affiliation: Department of Parasitology, Institute of Biomedical Sciences, University of São Paulo, São Paulo, Brazil.
authors.forename: Marcelo U
authors.initials: MU
authors.lastname: Ferreira
authors.affiliation: Department of Microbiology, Tumor and Cell Biology, Karolinska Institutet, Stockholm, Sweden.
authors.forename: Anders
authors.initials: A
authors.lastname: Björkman
authors.affiliation: Department of International Affairs and Tropical Medicine, Tokyo Women's Medical University, Tokyo, Japan.
authors.forename: Hiroyoshi
authors.initials: H
authors.lastname: Endo
authors.affiliation: Department of Biological Sciences, Graduate School of Science, The University of Tokyo, Tokyo, Japan.
authors.forename: Jun
authors.initials: J
authors.lastname: Ohashi
mesh_terms: D000962:Antimalarials / Q000494:pharmacology*; D037621:Artemisinins / Q000494:pharmacology*; D005828:Genetics, Population; D006801:Humans; D016778:Malaria, Falciparum / Q000469:parasitology; D009154:Mutation / Q000235:genetics; D010963:Plasmodium falciparum / Q000187:drug effects / Q000235:genetics*; D011110:Polymorphism, Genetic / Q000235:genetics*
chemical_list: D000962:Antimalarials; D037621:Artemisinins