RESUMO
Genome-wide association studies (GWAS) have now successfully identified important genetic variants associated with many human traits and diseases. The high cost of genotyping arrays in large data sets remains the major barrier to wider utilization of GWAS. We have developed a novel method in which whole blood from cases and controls, respectively, is pooled prior to DNA extraction for genotyping. We demonstrate proof of principle by clearly identifying the associated variants for eye color, age-related macular degeneration, and pseudoexfoliation syndrome in cohorts not previously studied. Blood pooling has the potential to reduce GWAS cost by several orders of magnitude and dramatically shorten gene discovery time. This method has profound implications for translation of modern genetic approaches to a multitude of diseases and traits yet to be analyzed by GWAS, and will enable developing nations to participate in GWAS.
Assuntos
Predisposição Genética para Doença/genética , Genoma Humano/genética , Estudo de Associação Genômica Ampla/métodos , Polimorfismo de Nucleotídeo Único , Coleta de Amostras Sanguíneas/métodos , Síndrome de Exfoliação/sangue , Síndrome de Exfoliação/genética , Cor de Olho/genética , Estudo de Associação Genômica Ampla/economia , Genótipo , Humanos , Degeneração Macular/sangue , Degeneração Macular/genética , Proteínas de Membrana Transportadoras , População Branca/genéticaRESUMO
PURPOSE: Pseudoexfoliation syndrome is a major risk factor for the development of glaucoma. Following recent reports of a strong association of coding variants in the lysyl oxidase-like 1 (LOXL1) gene with this syndrome but low penetrance and variable disease frequency between different populations, we aimed to identify additional genetic factors contributing to the disease. The clusterin (CLU) gene has been proposed as a candidate because of the presence of clusterin protein in pseudoexfoliation deposits, its varied levels in aqueous humor of cases compared to controls, and the role of the protein as a molecular chaperone. We investigated the association of genetic variants across CLU in pseudoexfoliation syndrome and analyzed molecular characteristics of the encoded protein in ocular tissues. METHODS: The expression of clusterin in relevant ocular tissues was assessed using western blotting. Nine tag single nucleotide polymorphisms (SNPs) across CLU were genotyped in 86 cases of pseudoexfoliation syndrome and 2422 controls from the Australian Blue Mountains Eye Study cohort. Each SNP and haplotype was assessed for association with the syndrome. RESULTS: Clusterin was identified in normal human iris, the ciliary body, lens capsule, optic nerve, and aqueous humor. Post-translational modification gives rise to a 100 kDa precursor protein in ocular tissues, larger than that reported in non-ocular tissues. One CLU SNP (rs3087554) was nominally associated with pseudoexfoliation syndrome at the genotypic level (p=0.044), although not when the age of controls was restricted to those over 73 years. Only age and the LOXL1 diplotype were significant factors in the logistic regression. One haplotype of all nine CLU SNPs was also associated (p=0.005), but the significance decreased slightly with the use of the age-restricted controls (p=0.011). CONCLUSIONS: Clusterin is present in ocular anterior segment tissues involved in pseudoexfoliation syndrome. Although one haplotype may contribute in a minor way to genetic risk of pseudoexfoliation syndrome, common variation in this gene is not a major contributor to the risk of pseudoexfoliation syndrome.
