title: Genotype-phenotype analysis of ABCR variants in macular degeneration probands and siblings.
abstract: OBJECTIVE
  Single-copy variants of the autosomal recessive Stargardt disease (STGD1) gene ABCR (ABCA4) have been shown to confer enhanced susceptibility to age-related macular degeneration (AMD). To investigate the role of ABCR alleles in AMD further, genotype-phenotype analysis was performed on siblings of patients with AMD who had known ABCR variants. This genetically related population provides a cohort of subjects with similar age and ethnic background for genotype-phenotype comparison to the original probands.
  
  
  METHODS
  All available siblings of 26 probands carrying probable disease-associated ABCR variants were examined clinically. Blood samples were collected from these siblings for genotype analysis to search for the ABCR variant alleles corresponding to the isofamilial proband.
  
  
  RESULTS
  Nineteen of 33 siblings from 15 families carried the respective proband's variant ABCR allele. Some families exhibited concordance of ABCR alleles with macular degeneration phenotype, but others did not. Exudative AMD was uncommon among both probands and siblings.
  
  
  CONCLUSIONS
  Although population studies have indicated that some ABCR variant alleles may enhance susceptibility to AMD, investigation of the extent of ABCR involvement by kindred analysis is complicated by a plethora of environmental and other hereditary factors not investigated in the current study that may also play important roles.
authors.affiliation: Department of Ophthalmology and Visual Sciences, Moran Eye Center, University of Utah School of Medicine, Salt Lake City, Utah 84132, USA. paul.berstein@hsc.utah.edu
authors.forename: Paul S
authors.initials: PS
authors.lastname: Bernstein
authors.forename: Mark
authors.initials: M
authors.lastname: Leppert
authors.forename: Nanda
authors.initials: N
authors.lastname: Singh
authors.forename: Michael
authors.initials: M
authors.lastname: Dean
authors.forename: Richard Alan
authors.initials: RA
authors.lastname: Lewis
authors.forename: James R
authors.initials: JR
authors.lastname: Lupski
authors.forename: Rando
authors.initials: R
authors.lastname: Allikmets
authors.forename: Johanna M
authors.initials: JM
authors.lastname: Seddon
mesh_terms: D018528:ATP-Binding Cassette Transporters / Q000235:genetics*; D000368:Aged; D000369:Aged, 80 and over; D004252:DNA Mutational Analysis; D005260:Female; D014644:Genetic Variation; D005838:Genotype; D006801:Humans; D008268:Macular Degeneration / Q000235:genetics* / Q000473:pathology*; D008297:Male; D008875:Middle Aged; D009154:Mutation; D009679:Nuclear Family; D010375:Pedigree; D010641:Phenotype
chemical_list: C056475:ABCA4 protein, human; D018528:ATP-Binding Cassette Transporters