title: [Combination of DRD4 and DAT1 genotypes is an important risk factor for attention deficit disorder with hyperactivity families living in Santiago, Chile].
abstract: BACKGROUND
  Attention deficit/hyperactivity disorder (ADHD) is a common, highly heritable neurobiological disorder of childhood onset, characterized by hyperactivity, impulsiveness, and/or inattentiveness.
  
  
  OBJECTIVE
  To search for possible associations between dopamine receptor D4 (DRD4) and dopamine transponder 1 (DATl) polymorphisms and ADHD in Chilean families.
  
  
  METHODS
  We extended a previous family-based discordant sib pair analysis that included 26 cases diagnosed according to DSM-IV criteria and 25 controls (healthy siblings of cases), adding 14 cases and 11 controls.
  
  
  RESULTS
  Both loci, individually classified as homozygotes or heterozygotes for the DRD4 7-repeat and DATl 10-repeat alleles, did not exhibit genotype frequency differences between affected children and their healthy siblings. However, the simultaneous presence of both DRD4 7-repeat heterozygosity and DATl 10 allele homozygosity was significantly higher (22.5%) in cases (40), compared with (2.8%) unaffected siblings (36), with an odds-ratio of 10.16.
  
  
  CONCLUSIONS
  The genotype combination DRD4/7 heterozygotes and DAT1/10 homozygotes is a high risk factors in Chilean families for ADHD. Increased density of dopamine transporters in ADHD brains, along with abundance of 7-repeat D4 receptors in prefrontal cortex, which is impaired in ADHD patients, make the observed gene-gene interaction worthy of studies to understand the functional basis of ADHD.
authors.affiliation: Centro de Alta Investigación, Universidad de Tarapacá, Arica, Chile.
authors.forename: Hugo
authors.initials: H
authors.lastname: Henríquez B
authors.forename: Marcela
authors.initials: M
authors.lastname: Henríquez H
authors.forename: Ximena
authors.initials: X
authors.lastname: Carrasco Ch
authors.forename: Paula
authors.initials: P
authors.lastname: Rothhammer A
authors.forename: Elena
authors.initials: E
authors.lastname: Llop R
authors.forename: Francisco
authors.initials: F
authors.lastname: Aboitiz
authors.forename: Francisco
authors.initials: F
authors.lastname: Rothhammer E