title: [Gene point mutation in the dihydrofolate reductase-thymidylate synthase gene of Plasmodium falciparum].
abstract: OBJECTIVE
  To investigate the gene point mutation in the dihydrofolate reductase-thymidylate synthase(dhfr) gene of Plasmodium falciparum isolate from Yunnan Province strongly associated with pyrimethamine and cycloguanil resistance.
  
  
  METHODS
  Nested PCR and restriction endonuclease digestion were applied to detect the gene mutation using dried blood filter paper collected from the fields in Yunnan Province.
  
  
  RESULTS
  Different mutations were found in 4 amino acids at positions 16, 51, 108 and 164 of dhfr gene, particularly, Asn-108 and Ile-51, the mutation frequency being 94.1% and 90.1%, respectively. The frequency of the wild-type genotype (3D7-type) Ser-108 appeared lower (9.1%), while the frequency of the Ala-16 was high(61.8%); the mutation-type was very high, the ratio of HB3-type, 7G8-type/FCR3-type and Cambodian-type was 1:21:7.5.
  
  
  CONCLUSIONS
  The investigation first demonstrated that Plasmodium falciparum Yunnan isolate dihydrofolate reductase-thymidylate synthase gene (dhfr) at positions 16, 51, 108 and 164 exhibited different degrees of point mutation. The frequency of mutation of the 7D8-type involved in pyrimethamine resistance was higher, while that of the FCR3-type involved in cycloquanil resistance was lower.
authors.affiliation: Yunnan Institute of Malaria Control, Simao 665000.
authors.forename: Z X
authors.initials: ZX
authors.lastname: Zhang
authors.forename: Y M
authors.initials: YM
authors.lastname: Yang
authors.forename: H
authors.initials: H
authors.lastname: Liu
mesh_terms: D000818:Animals; D004351:Drug Resistance / Q000235:genetics; D009097:Multienzyme Complexes / Q000235:genetics*; D010963:Plasmodium falciparum / Q000201:enzymology / Q000235:genetics*; D017354:Point Mutation; D016133:Polymerase Chain Reaction; D012150:Polymorphism, Restriction Fragment Length; D002727:Proguanil; D011739:Pyrimethamine / Q000494:pharmacology; D013762:Tetrahydrofolate Dehydrogenase / Q000235:genetics*; D013940:Thymidylate Synthase / Q000235:genetics*; D014227:Triazines / Q000494:pharmacology
chemical_list: D009097:Multienzyme Complexes; D014227:Triazines; C056930:thymidylate synthase-dihydrofolate reductase; C026009:cycloguanil; D013762:Tetrahydrofolate Dehydrogenase; D013940:Thymidylate Synthase; D002727:Proguanil; D011739:Pyrimethamine