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Original Investigation
November 5, 2019

Association of Genetic Variants With Primary Open-Angle Glaucoma Among Individuals With African Ancestry

The Genetics of Glaucoma in People of African Descent (GGLAD) Consortium
JAMA. 2019;322(17):1682-1691. doi:10.1001/jama.2019.16161
Key Points

Question  Are there differences in genetic risk factors for primary open-angle glaucoma based on ancestry?

Findings  In this multistage, case-control, genome-wide association study that included 26 295 participants, the amyloid-β A4 precursor protein-binding family B member 2 (APBB2) locus was significantly associated with primary open-angle glaucoma among individuals of African ancestry (odds ratio, 1.19 per copy of the risk allele for single-nucleotide polymorphism rs59892895T>C), but not of European or Asian ancestry.

Meaning  This study identified a single-nucleotide polymorphism that demonstrated differential association with primary open-angle glaucoma by ancestry.

Abstract

Importance  Primary open-angle glaucoma presents with increased prevalence and a higher degree of clinical severity in populations of African ancestry compared with European or Asian ancestry. Despite this, individuals of African ancestry remain understudied in genomic research for blinding disorders.

Objectives  To perform a genome-wide association study (GWAS) of African ancestry populations and evaluate potential mechanisms of pathogenesis for loci associated with primary open-angle glaucoma.

Design, Settings, and Participants  A 2-stage GWAS with a discovery data set of 2320 individuals with primary open-angle glaucoma and 2121 control individuals without primary open-angle glaucoma. The validation stage included an additional 6937 affected individuals and 14 917 unaffected individuals using multicenter clinic- and population-based participant recruitment approaches. Study participants were recruited from Ghana, Nigeria, South Africa, the United States, Tanzania, Britain, Cameroon, Saudi Arabia, Brazil, the Democratic Republic of the Congo, Morocco, Peru, and Mali from 2003 to 2018. Individuals with primary open-angle glaucoma had open iridocorneal angles and displayed glaucomatous optic neuropathy with visual field defects. Elevated intraocular pressure was not included in the case definition. Control individuals had no elevated intraocular pressure and no signs of glaucoma.

Exposures  Genetic variants associated with primary open-angle glaucoma.

Main Outcomes and Measures  Presence of primary open-angle glaucoma. Genome-wide significance was defined as P < 5 × 10−8 in the discovery stage and in the meta-analysis of combined discovery and validation data.

Results  A total of 2320 individuals with primary open-angle glaucoma (mean [interquartile range] age, 64.6 [56-74] years; 1055 [45.5%] women) and 2121 individuals without primary open-angle glaucoma (mean [interquartile range] age, 63.4 [55-71] years; 1025 [48.3%] women) were included in the discovery GWAS. The GWAS discovery meta-analysis demonstrated association of variants at amyloid-β A4 precursor protein-binding family B member 2 (APBB2; chromosome 4, rs59892895T>C) with primary open-angle glaucoma (odds ratio [OR], 1.32 [95% CI, 1.20-1.46]; P = 2 × 10−8). The association was validated in an analysis of an additional 6937 affected individuals and 14 917 unaffected individuals (OR, 1.15 [95% CI, 1.09-1.21]; P < .001). Each copy of the rs59892895*C risk allele was associated with increased risk of primary open-angle glaucoma when all data were included in a meta-analysis (OR, 1.19 [95% CI, 1.14-1.25]; P = 4 × 10−13). The rs59892895*C risk allele was present at appreciable frequency only in African ancestry populations. In contrast, the rs59892895*C risk allele had a frequency of less than 0.1% in individuals of European or Asian ancestry.

Conclusions and Relevance  In this genome-wide association study, variants at the APBB2 locus demonstrated differential association with primary open-angle glaucoma by ancestry. If validated in additional populations this finding may have implications for risk assessment and therapeutic strategies.

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