title: Genetic and environmental factors in conjunctival UV autofluorescence.
abstract: OBJECTIVE
  Conjunctival UV autofluorescence (CUVAF) photography was developed to detect and characterize preclinical sunlight-induced ocular damage. Ocular sun exposure has been related to cases of pterygia and was recently negatively correlated with myopia. Hence, CUVAF has excellent potential as an objective biomarker of sun exposure. However, much variation in CUVAF has been observed, and the relative contributions of genes and environment to this variation have not yet been identified.
  
  
  OBJECTIVE
  To investigate sources of variation in CUVAF in relation to its potential clinical relevance.
  
  
  METHODS
  We performed a cross-sectional analysis of 3 population-based cohort studies in the general community, including the Twins Eye Study in Tasmania, the Brisbane Adolescent Twin Study, and the Western Australian Pregnancy Cohort (Raine) Study. The twin studies were conducted between 2001 and 2009, and the 20-year follow-up of the Raine Study was completed between March 2010 and February 2012. We included genotypic and phenotypic data from 295 Australian families in the Tasmanian and Brisbane twin studies and from 661 participants in the 20-year follow-up of the Raine Study. We compared CUVAF levels in the 3 cohorts and performed a classic twin study to partition variation in CUVAF. We also conducted a genome-wide association analysis to identify specific genetic variants associated with CUVAF.
  
  
  METHODS
  The total area of CUVAF, heritability of CUVAF, and single-nucleotide polymorphisms (SNPs) associated with CUVAF from the genome-wide association study.
  
  
  RESULTS
  Within twin cohorts, individuals living closer to the equator (latitude, 27.47° S) had higher levels of CUVAF compared with individuals from southern regions (latitude, 42.88° S) (median [interquartile range], 45.4 [26.8-68.5] vs 28.7 [15.0-42.3] mm2; P < .001). The variation in CUVAF explained by the additive genetic component was 0.37 (95% CI, 0.22-0.56), whereas the variation due to the common environment was 0.50 (95% CI; 0.29-0.71). The SNP rs1060043, located approximately 800 base pairs away from the SLC1A5 gene, a member of the solute carrier family 1, had a genome-wide significant association with a P value of 3.2 × 10-8. Gene-based analysis did not improve our power to detect association with other genes.
  
  
  CONCLUSIONS
  Our findings confirm that, although a large environmental component to CUVAF (equivalent of sun exposure) exists, genes also play a significant role. We identified a SNP (rs1060043) as being significantly associated with CUVAF; replication of this finding in future studies is warranted.
authors.affiliation: Centre for Ophthalmology and Vision Science/Lions Eye Institute Perth, University of Western Australia, Perth, Australia.
authors.forename: Seyhan
authors.initials: S
authors.lastname: Yazar
authors.affiliation: Statistical Genetics, QIMR Berghofer Medical Research Institute, Brisbane, Australia.
authors.forename: Gabriel
authors.initials: G
authors.lastname: Cuellar-Partida
authors.affiliation: Centre for Ophthalmology and Vision Science/Lions Eye Institute Perth, University of Western Australia, Perth, Australia.
authors.forename: Charlotte M
authors.initials: CM
authors.lastname: McKnight
authors.affiliation: Centre for Ophthalmology and Vision Science/Lions Eye Institute Perth, University of Western Australia, Perth, Australia.
authors.forename: Piriya
authors.initials: P
authors.lastname: Quach-Thanissorn
authors.affiliation: Telethon Kids Institute, University of Western Australia, Perth, Australia.
authors.forename: Jenny A
authors.initials: JA
authors.lastname: Mountain
authors.affiliation: Department of Ophthalmology, University of New South Wales, Sydney, Australia.
authors.forename: Minas T
authors.initials: MT
authors.lastname: Coroneo
authors.affiliation: School of Women's and Infants' Health, University of Western Australia, Perth, Australia.
authors.forename: Craig E
authors.initials: CE
authors.lastname: Pennell
authors.affiliation: Centre for Eye Research Australia, Melbourne University, Melbourne, Australia.
authors.forename: Alex W
authors.initials: AW
authors.lastname: Hewitt
authors.affiliation: Statistical Genetics, QIMR Berghofer Medical Research Institute, Brisbane, Australia.
authors.forename: Stuart
authors.initials: S
authors.lastname: MacGregor
authors.affiliation: Centre for Ophthalmology and Vision Science/Lions Eye Institute Perth, University of Western Australia, Perth, Australia6Centre for Eye Research Australia, Melbourne University, Melbourne, Australia.
authors.forename: David A
authors.initials: DA
authors.lastname: Mackey
mesh_terms: D000293:Adolescent; D000328:Adult; D001315:Australia; D002648:Child; D002675:Child, Preschool; D015331:Cohort Studies; D003228:Conjunctiva / Q000528:radiation effects*; D003430:Cross-Sectional Studies; D004200:Diseases in Twins / Q000235:genetics*; D004781:Environmental Exposure; D005260:Female; D059647:Gene-Environment Interaction; D020022:Genetic Predisposition to Disease; D005823:Genetics; D055106:Genome-Wide Association Study; D060005:Genotyping Techniques; D005843:Geography; D006801:Humans; D008297:Male; D008875:Middle Aged; D061848:Optical Imaging / Q000379:methods; D010781:Photography; D020641:Polymorphism, Single Nucleotide; D011832:Radiation Injuries / Q000175:diagnosis / Q000209:etiology / Q000235:genetics*; D013472:Sunlight / Q000009:adverse effects; D011795:Surveys and Questionnaires; D014429:Twins, Dizygotic; D014430:Twins, Monozygotic; D014466:Ultraviolet Rays / Q000009:adverse effects*; D055815:Young Adult