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Editors Selection IGR 7-2
Basic research: Genes and IOP
Comment by John Fingert on:
14055 Genomewide scan and fine mapping of quantitative trait loci for intraocular pressure on 5q and 14q in West Africans, Rotimi CN; Chen G; Adeyemo AA et al., Investigative Ophthalmology and Visual Science, 2006; 47: 3262-3267
Rotimi et al. (686)reported a novel application of sib-pair studies to identify genetic loci that are important in glaucoma. A variety of linkage analysis-based methods have been used to identify the chromosomal location of genes associated with glaucoma including studies of large glaucoma pedigrees, studies of sib-pairs with glaucoma, and studies of glaucoma pedigrees with ordered subset analysis. Prior linkage studies were all designed to seek associations between a diagnosis of glaucoma and the inheritance of genetic markers. In contrast to this approach, the authors utilized a cohort of subjects that don't have glaucoma to search for associations between the magnitude of intraocular pressure (IOP) and genetic markers. A genomewide scan was conducted to identify the chromosomal position of genes that determine IOP, i.e., quantitative trait loci (QTL's) for IOP. Genotyping 244 West African sib-pairs (previously ascertained for a study of type II diabetes) with 372 short tandem repeat polymorphsim (STRP) markers identified QTL's for IOP on chromsome 5q22 and 14q22. These loci presumably contain genes with a role in IOP regulation.
The identification of a QTL for IOP on chromosome 5q22 is of particular interest, because it provides additional support for recent studies that suggest the presence of one or more glaucoma-causing genes on chromosome 5q. In 2005, Monemi et al. reported linkage of several glaucoma pedigrees to a genetic locus designated GLC1G on chromosome 5q22. The WDR36 gene has been reported to be the glaucoma-causing gene in the GLC1G locus,1 however, this report has not been confirmed. More recently, in 2006, Pang et al. reported linkage of a single glaucoma pedigree to chromosome 5q22.1-q32, which does not overlap with the GLC1G locus and does not contain the WDR36 gene.2 It is interesting to note that the QTL for IOP identified by Rotimi et al. is centered on the GLC1G locus (which contains the WDR36 gene) and encompasses the nearby but distinct glaucoma locus identified by Pang et al.Taken together these reports strengthen the notion that a gene (or genes) on chromosome 5q plays an important role in regulation of IOP and the pathophysiology of glaucoma.
References
- Monemi, S. et al. Identification of a novel adult-onset primary open-angle glaucoma (POAG) gene on 5q22.1. Hum Mol Genet 14, 725-33 (2005).
- Pang, C.P. et al. A genome-wide scan maps a novel juvenile-onset primary open angle glaucoma locus to chromosome 5q. Mol Vis 12, 85-92 (2006).
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