Multi-tissue transcriptome-wide association study identifies novel candidate susceptibility genes for cataract.

Introduction: Cataract is the leading cause of blindness among the elderly worldwide. Twin and family studies support an important role for genetic factors in cataract susceptibility with heritability estimates up to 58%. To date, 55 loci for cataract have been identified by genome-wide association studies (GWAS), however, much work remains to identify the causal genes. Here, we conducted a transcriptome-wide association study (TWAS) of cataract to prioritize causal genes and identify novel ones, and examine the impact of their expression. Methods: We performed tissue-specific and multi-tissue TWAS analyses to assess associations between imputed gene expression from 54 tissues (including 49 from the Genotype Tissue Expression (GTEx) Project v8) with cataract using FUSION software. Meta-analyzed GWAS summary statistics from 59,944 cataract cases and 478,571 controls, all of European ancestry and from two cohorts (GERA and UK Biobank) were used. We then examined the expression of the novel genes in the lens tissue using the iSyTE database. Results: Across tissue-specific and multi-tissue analyses, we identified 99 genes for which genetically predicted gene expression was associated with cataract after correcting for multiple testing. Of these 99 genes, 20 (AC007773.1, ANKH, ASIP, ATP13A2, CAPZB, CEP95, COQ6, CREB1, CROCC, DDX5, EFEMP1, EIF2S2, ESRRB, GOSR2, HERC4, INSRR, NIPSNAP2, PICALM, SENP3, and SH3YL1) did not overlap with previously reported cataract-associated loci. Tissue-specific analysis identified 202 significant gene-tissue associations for cataract, of which 166 (82.2%), representing 9 unique genes, were attributed to the previously reported 11q13.3 locus. Tissue-enrichment analysis revealed that gastrointestinal tissues represented one of the highest proportions of the Bonferroni-significant gene-tissue associations (21.3%). Moreover, this gastrointestinal tissue type was the only anatomical category significantly enriched in our results, after correcting for the number of tissue donors and imputable genes for each reference panel. Finally, most of the novel cataract genes (e.g., Capzb) were robustly expressed in iSyTE lens data. Discussion: Our results provide evidence of the utility of imputation-based TWAS approaches to characterize known GWAS risk loci and identify novel candidate genes that may increase our understanding of cataract etiology. Our findings also highlight the fact that expression of genes associated with cataract susceptibility is not necessarily restricted to lens tissue.

Association of Behavioral and Clinical Risk Factors With Cataract: A Two-Sample Mendelian Randomization Study.

Purpose: To investigate the association of genetically determined primary open-angle glaucoma (POAG), myopic refractive error (RE), type 2 diabetes (T2D), blood pressure (BP), body mass index (BMI), cigarette smoking, and alcohol consumption with the risk of age-related cataract. Methods: To assess potential causal effects of clinical or behavioral factors on cataract risk, we conducted two-sample Mendelian randomization analyses. Genetic instruments, based on common genetic variants associated with risk factors at genome-wide significance (P < 5 × 10-8), were derived from published genome-wide association studies (GWAS). For age-related cataract, we used GWAS summary statistics from our previous GWAS conducted in the Genetic Epidemiology Research on Adult Health and Aging (GERA) cohort (28,092 cataract cases and 50,487 controls; all non-Hispanic whites) or in the UK Biobank (31,852 cataract cases and 428,084 controls; all European-descent individuals). We used the inverse-variance weighted (IVW) method as our primary source of Mendelian randomization estimates and conducted common sensitivity analyses. Results: We found that genetically determined POAG and mean spherical equivalent RE were significantly associated with cataract risk (IVW model: odds ratio [OR] = 1.04; 95% confidence interval [CI], 1.01-1.08; P = 0.018; per diopter more hyperopic: OR = 0.92; 95% CI, 0.89-0.93; P = 6.51 × 10-13, respectively). In contrast, genetically determined T2D, BP, BMI, cigarette smoking, or alcohol consumption were not associated with cataract risk (P > 0.05). Conclusions: Our results provide evidence that genetic risks for POAG and myopia may be causal risk factors for age-related cataract. These results are consistent with previous observational studies reporting associations of myopia with cataract risk. This information may support population cataract risk stratification and screening strategies.

Primary trabeculectomy surgery performed by residents at a county hospital.

PURPOSE: To evaluate the safety and efficacy of trabeculectomies performed by ophthalmology residents at a metropolitan county hospital, under the supervision of attending physicians. METHODS: A retrospective analysis of resident-performed trabeculectomies at the San Francisco General Hospital from the period of 1994 to 2004 was performed. The preoperative and postoperative ocular data of 50 eyes in 35 patients were evaluated. Of the 50 cases, 47 procedures were performed as primary trabeculectomies and 3 were revisions of trabeculectomies. RESULTS: The average follow-up period was 28.9+/-17.6 months with an intraocular pressure (IOP) decrease from 23.2+/-9.4 mm Hg preoperatively to 11.3+/-4.4 mm Hg at last follow-up, for a mean reduction of 11.9+/-10.5 mm Hg (51.6%) (P<0.0001). Follow-up periods ranged from 3 months to over 6 years. The number of medications required decreased from 3.2+/-1.1 to 0.6+/-0.1 (P<0.0001). Success, defined by a postoperative IOP < or =21 mm Hg or a decreased postoperative IOP of at least 25% from preoperative pressure if the preoperative IOP was already < or =21 mm Hg, was observed in 42 eyes (84%) at last follow-up. Best-corrected visual acuity was stable or improved in 22 eyes (44%) and was noted to decrease 2 or more Snellen lines in 28 eyes (56%). Notable complications included 3 cases (6%) of persistent hypotony (IOP<5), 1 case (2%) of late endophthalmitis, and 1 case (2%) of phthisis. Seven eyes (14%) required subsequent penetrating glaucoma procedures due to bleb failure. CONCLUSIONS: Results of this study suggest that the outcomes of trabeculectomies performed by residents at a county hospital can have a high success rate, comparable with previous studies in the literature. Rates of complications are overall similar to those found in the published literature.

Screening for retinoblastoma: presenting signs as prognosticators of patient and ocular survival.

OBJECTIVE: To correlate 3 common presenting signs of retinoblastoma with patient and ocular survival and to assess the efficacy of current pediatric screening practices for retinoblastoma. METHODS: A retrospective study was conducted of 1831 retinoblastoma patients from our center (1914-June 2000). Patient survival (excluding deaths from other primary neoplasms) and ocular survival (presenting eyes) rates were calculated and analyzed using the Kaplan-Meier method. RESULTS: Leukocoria correlated with excellent patient survival (>86%, 5 years) but poor ocular survival in unilateral (4%, 5 years) and bilateral patients (29%, 5 years). A total of 308 (19%) of 1654 patients presented with strabismus: patient survival was excellent (90%, 5 years), and ocular survival was poor (17%, 5 years) yet better than leukocoria. Patients who had a family history of retinoblastoma and were clinically screened for retinal tumors from birth were diagnosed younger (8 months of age) and earlier (Reese Ellsworth group 1 = 26 [58%] of 45) and had better ocular survival than nonscreened patients with a family history. More patients were initially detected by family/friends (1315 [80%] of 1632) than pediatricians (123 [8%] of 1632) or ophthalmologists (156 [10%] of 1632). CONCLUSION: Most US children whose retinoblastoma is diagnosed initially present with leukocoria detected by a parent, despite routine pediatric screening for leukocoria via the red reflex test. Initial disease detection at the point of leukocoria or strabismus correlated with high patient survival rates and poor ocular survival rates for the presenting eye. Saving eyes and vision requires disease recognition before leukocoria, as demonstrated by the better ocular salvage rate among patients who had a positive family history and received clinical surveillance via early, routine dilated funduscopic examinations by an ophthalmologist.