title: [Gene polymorphisms in the dihydrofolate reductase ( dhfr ) and dihydropteroate synthase ( dhps ) genes and structural modelling of the dhps gene in Colombian isolates of Toxoplasma gondii].
abstract: BACKGROUND
  There are no reports describing polymorphisms in target genes of anti- Toxoplasma drugs in South American isolates.
  
  
  OBJECTIVE
  This study sought to perform cloning and sequencing of the dihydrofolate reductase ( dhfr ) and dihydropteroate-synthase ( dhps ) genes of the reference Rh strain and two Colombian isolates of Toxoplasma gondii .
  
  
  METHODS
  Two isolates were obtained from the cerebrospinal fluid of HIV-infected patients with cerebral toxoplasmosis. A DNA extraction technique and PCR assay for the dhfr and dhps genes were standardized, and the products of amplification were cloned into Escherichia coli and sequenced.
  
  
  RESULTS
  One polymorphism (A « G) was found at position 235 of exon 2 in the dhps gene. In addition, two polymorphisms (G « C) at positions 259 and 260 and one polymorphism (T « G) at position 371 within exon 4 of the dhps gene were detected. In this last exon, a bioinformatic analysis revealed a non-synonymous polymorphism in the coding region that could lead to the substitution of Glu (CAA or CAG) for His (encoded by codons AAU or AAC). A structural model of the T. gondii DHPS protein was calculated, and the results revealed modifications in secondary structure due to mutations.
  
  
  CONCLUSIONS
  The methods described in this study can be used as a tool to search for polymorphisms in samples from patients with different clinical manifestations of toxoplasmosis and to examine their relationship with the therapeutic response.
authors.affiliation: Grupo de Parasitología, Subdirección de Investigación Científica y Tecnológica, Instituto Nacional de Salud.
authors.forename: Liliana Jazmín
authors.initials: LJ
authors.lastname: Cortés
authors.affiliation: Grupo de Parasitología, Subdirección de Investigación Científica y Tecnológica, Instituto Nacional de Salud.
authors.forename: Sofía
authors.initials: S
authors.lastname: Duque
authors.affiliation: Departamento de Parasitología, Facultad de Medicina, Universidad Nacional de Colombia, Bogotá, D.C, Colombia.
authors.forename: Miryam Consuelo
authors.initials: MC
authors.lastname: López
authors.affiliation: Grupo de Parasitología Molecular (GEPAMOL), Centro de Investigaciones Biomédicas, Universidad del Quindío, Armenia, Colombia.
authors.forename: Diego
authors.initials: D
authors.lastname: Moncada
authors.affiliation: Grupo de Parasitología, Subdirección de Investigación Científica y Tecnológica, Instituto Nacional de Salud.
authors.forename: Diego
authors.initials: D
authors.lastname: Molina
authors.affiliation: Grupo de Parasitología Molecular (GEPAMOL), Centro de Investigaciones Biomédicas, Universidad del Quindío, Armenia, Colombia.
authors.forename: Jorge Enrique
authors.initials: JE
authors.lastname: Gómez-Marín
authors.affiliation: Grupo de Fisiología Molecular, Subdirección de Investigación Científica y Tecnológica, Instituto Nacional de Salud, Bogotá, D.C, Colombia.
authors.forename: María Luz
authors.initials: ML
authors.lastname: Gunturiz
mesh_terms: D017088:AIDS-Related Opportunistic Infections / Q000134:cerebrospinal fluid / Q000469:parasitology; D019943:Amino Acid Substitution; D000818:Animals; D001483:Base Sequence; D002555:Cerebrospinal Fluid / Q000469:parasitology; D003001:Cloning, Molecular; D003105:Colombia; D016054:DNA, Protozoan / Q000235:genetics; D004274:DNA, Recombinant / Q000235:genetics; D004094:Dihydropteroate Synthase / Q000737:chemistry / Q000235:genetics*; D005091:Exons / Q000235:genetics; D006801:Humans; D008297:Male; D051379:Mice; D008958:Models, Molecular; D008969:Molecular Sequence Data; D020641:Polymorphism, Single Nucleotide; D011487:Protein Conformation; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics*; D016415:Sequence Alignment; D012689:Sequence Homology, Nucleic Acid; D013762:Tetrahydrofolate Dehydrogenase / Q000235:genetics*; D014122:Toxoplasma / Q000201:enzymology* / Q000235:genetics / Q000302:isolation & purification; D014124:Toxoplasmosis, Animal / Q000469:parasitology; D016781:Toxoplasmosis, Cerebral / Q000134:cerebrospinal fluid / Q000469:parasitology
chemical_list: D016054:DNA, Protozoan; D004274:DNA, Recombinant; D015800:Protozoan Proteins; D013762:Tetrahydrofolate Dehydrogenase; D004094:Dihydropteroate Synthase