Adult-onset primary open angle glaucoma does not localize to chromosome 2cen-q13 in North American families

Gene mapping for primary open angle glaucoma

Primary open angle glaucoma (POAG) is a leading cause of visual impairment and blindness worldwide. To date, at least 20 genetic loci for POAG have been reported. Only 3 causative genes are identified from these loci: myocilin (MYOC), optineurin (OPTN) and WD repeat domain 36 (WDR36), which together account for less than 10% of POAG. Only a portion of POAG follows Mendelian inheritance, and a considerable fraction results from a large number of variants in several genes, each contributing small effects. Over the past 10 years, there has been vigorous research on mapping the POAG genes. The main technological approaches are functional cloning, family linkage analysis, genome-wide scan, case-control association study, and microarray analysis. Association studies found 16 genes related to POAG, but reports on glaucoma-causing effects of these genes are conflicting. Ten microarray gene expression studies related to POAG have been published. A number of genes potentially related to POAG have been identified, and they provide a good resource to select candidate genes for mutation analysis in association studies. While linkage studies remain a mainstay, the current trend is to use genome-wide association studies to map genes for POAG. This review gives an overview of the efforts in the past decade to identify the POAG genes through linkage studies, genome-wide scans, case-control association studies and microarray studies. In the near future such comprehensive studies are expected to greatly advance our understanding of the genetic basis of POAG and provide information for effective glaucoma therapy.

Patterns of open-angle glaucoma in the Barbados Family Study

OBJECTIVE

To describe the Barbados Family Study of open-angle glaucoma (OAG) and present risk factors for OAG in siblings of study probands.

DESIGN

Observational study of families of probands with OAG.

PARTICIPANTS

Two hundred thirty probands and 1056 relatives (from 207 families).

METHODS

Probands and their family members underwent standardized examinations, including automated perimetry, applanation tonometry, ophthalmologic evaluation, fundus photography, blood pressure, interview, and genotyping. Generalized estimation equation methods were used to evaluate risk factors.

MAIN OUTCOME MEASURES

Presence of OAG in the relatives, as defined by both visual field and optic disc findings, after ophthalmologic exclusion of other causes.

RESULTS

The median ages of probands and relatives were 68 and 47 years, respectively. In the 207 families, 29% of the probands had one relative with OAG and 10% had two or more relatives affected. Of the 1056 family members, 10% had OAG, 13% had suspect OAG, and 6% had ocular hypertension. One fifth of the 338 siblings had OAG (n = 67); they tended to be older and more often were male. Multivariate comparisons between siblings with and without OAG found that age, higher intraocular pressure (IOP), myopia, and lower diastolic blood pressure-IOP differences were related to OAG, whereas hypertension and diabetes were not.

CONCLUSIONS

Based on standardized protocols and examinations, approximately one quarter of the relatives had OAG or suspected OAG, despite their relatively young age. Risk factors for OAG in siblings were similar to risk factors in unrelated individuals. Analyses are ongoing to determine OAG inheritance and to localize potential gene(s) involved.