Discordant patterns of genetic variation at two chloroquine resistance loci in worldwide populations of the malaria parasite Plasmodium falciparum.
Mutations in the chloroquine resistance (CQR) transporter gene of Plasmodium falciparum (Pfcrt; chromosome 7) play a key role in CQR, while mutations in the multidrug resistance gene (Pfmdr1; chromosome 5) play a significant role in the parasite's resistance to a variety of antimalarials and also modulate CQR. To compare patterns of genetic variation at Pfcrt and Pfmdr1 loci, we investigated 460 blood samples from P. falciparum-infected patients from four Asian, three African, and three South American countries, analyzing microsatellite (MS) loci flanking Pfcrt (five loci [approximately 40 kb]) and Pfmdr1 (either two loci [approximately 5 kb] or four loci [approximately 10 kb]). CQR Pfmdr1 allele-associated MS haplotypes showed considerably higher genetic diversity and higher levels of subdivision than CQR Pfcrt allele-associated MS haplotypes in both Asian and African parasite populations. However, both Pfcrt and Pfmdr1 MS haplotypes showed similar levels of low diversity in South American parasite populations. Median-joining network analyses showed that the Pfcrt MS haplotypes correlated well with geography and CQR Pfcrt alleles, whereas there was no distinct Pfmdr1 MS haplotype that correlated with geography and/or CQR Pfmdr1 alleles. Furthermore, multiple independent origins of CQR Pfmdr1 alleles in Asia and Africa were inferred. These results suggest that variation at Pfcrt and Pfmdr1 loci in both Asian and African parasite populations is generated and/or maintained via substantially different mechanisms. Since Pfmdr1 mutations may be associated with resistance to artemisinin combination therapies that are replacing CQ, particularly in Africa, it is important to determine if, and how, the genetic characteristics of this locus change over time.
Mehlotra
Rajeev K
RK
Center for Global Health and Diseases, Case Western Reserve University, School of Medicine, Wolstein Research Building, room no. 4204, 2103 Cornell Road, Cleveland, OH 44106-7286, USA. rkm@case.edu
Mattera
Gabriel
G
Bockarie
Moses J
MJ
Maguire
Jason D
JD
Baird
J Kevin
JK
Sharma
Yagya D
YD
Alifrangis
Michael
M
Dorsey
Grant
G
Rosenthal
Philip J
PJ
Fryauff
David J
DJ
Kazura
James W
JW
Stoneking
Mark
M
Zimmerman
Peter A
PA
D018528:ATP-Binding Cassette Transporters / Q000235:genetics*; D000349:Africa / Q000453:epidemiology; D000818:Animals; D000962:Antimalarials / Q000494:pharmacology*; D001208:Asia / Q000453:epidemiology; D002738:Chloroquine / Q000494:pharmacology*; D004351:Drug Resistance / Q000235:genetics*; D014644:Genetic Variation; D006239:Haplotypes; D006801:Humans; D016778:Malaria, Falciparum / Q000453:epidemiology / Q000469:parasitology; D026901:Membrane Transport Proteins / Q000235:genetics*; D010963:Plasmodium falciparum / Q000145:classification / Q000187:drug effects* / Q000235:genetics; D015995:Prevalence; D015800:Protozoan Proteins / Q000235:genetics*; D013020:South America / Q000453:epidemiology
D018528:ATP-Binding Cassette Transporters; D000962:Antimalarials; D026901:Membrane Transport Proteins; C416369:PfCRT protein, Plasmodium falciparum; D015800:Protozoan Proteins; C059987:mdr gene protein, Plasmodium; D002738:Chloroquine