title: Bivariate linkage scan for reading disability and attention-deficit/hyperactivity disorder localizes pleiotropic loci.
abstract: BACKGROUND
  There is a growing interest in the study of the genetic origins of comorbidity, a direct consequence of the recent findings of genetic loci that are seemingly linked to more than one disorder. There are several potential causes for these shared regions of linkage, but one possibility is that these loci may harbor genes with manifold effects. The established genetic correlation between reading disability (RD) and attention-deficit/hyperactivity disorder (ADHD) suggests that their comorbidity is due at least in part to genes that have an impact on several phenotypes, a phenomenon known as pleiotropy.
  
  
  METHODS
  We employ a bivariate linkage test for selected samples that could help identify these pleiotropic loci. This linkage method was employed to carry out the first bivariate genome-wide analysis for RD and ADHD, in a selected sample of 182 sibling pairs.
  
  
  RESULTS
  We found evidence for a novel locus at chromosome 14q32 (multipoint LOD=2.5; singlepoint LOD=3.9) with a pleiotropic effect on RD and ADHD. Another locus at 13q32, which had been implicated in previous univariate scans of RD and ADHD, seems to have a pleiotropic effect on both disorders. 20q11 is also suggested as a pleiotropic locus. Other loci previously implicated in RD or ADHD did not exhibit bivariate linkage.
  
  
  CONCLUSIONS
  Some loci are suggested as having pleiotropic effects on RD and ADHD, while others might have unique effects. These results highlight the utility of this bivariate linkage method to study pleiotropy.
authors.affiliation: Wellcome Trust Centre for Human Genetics, University of Oxford, UK. gayan@well.ox.ac.uk
authors.forename: J
authors.initials: J
authors.lastname: Gayán
authors.forename: E G
authors.initials: EG
authors.lastname: Willcutt
authors.forename: S E
authors.initials: SE
authors.lastname: Fisher
authors.forename: C
authors.initials: C
authors.lastname: Francks
authors.forename: L R
authors.initials: LR
authors.lastname: Cardon
authors.forename: R K
authors.initials: RK
authors.lastname: Olson
authors.forename: B F
authors.initials: BF
authors.lastname: Pennington
authors.forename: S D
authors.initials: SD
authors.lastname: Smith
authors.forename: A P
authors.initials: AP
authors.lastname: Monaco
authors.forename: J C
authors.initials: JC
authors.lastname: DeFries
mesh_terms: D000293:Adolescent; D001289:Attention Deficit Disorder with Hyperactivity / Q000453:epidemiology* / Q000235:genetics*; D002648:Child; D003120:Colorado / Q000453:epidemiology; D015897:Comorbidity; D004410:Dyslexia / Q000453:epidemiology* / Q000235:genetics*; D005260:Female; D008040:Genetic Linkage / Q000235:genetics*; D006801:Humans; D008297:Male; D015999:Multivariate Analysis; D012044:Regression Analysis; D035781:Siblings