Mapping of the Disease Locus and Identification of ADAMTS10 As a Candidate Gene in a Canine Model of Primary Open Angle Glaucoma

John Kuchtey,Rachel W Kuchtey,Kirk N Gelatt,Edward O Mackay,Lana M Olson,Jonathan L Haines,Tommy Rinkoski,T M Iverson,Gregory S Barsh

doi:10.1371/journal.pgen.1001306

Abstract

Primary open angle glaucoma (POAG) is a leading cause of blindness worldwide, with elevated intraocular pressure as an important risk factor. Increased resistance to outflow of aqueous humor through the trabecular meshwork causes elevated intraocular pressure, but the specific mechanisms are unknown. In this study, we used genome-wide SNP arrays to map the disease gene in a colony of Beagle dogs with inherited POAG to within a single 4 Mb locus on canine chromosome 20. The Beagle POAG locus is syntenic to a previously mapped human quantitative trait locus for intraocular pressure on human chromosome 19. Sequence capture and next-generation sequencing of the entire canine POAG locus revealed a total of 2,692 SNPs segregating with disease. Of the disease-segregating SNPs, 54 were within exons, 8 of which result in amino acid substitutions. The strongest candidate variant causes a glycine to arginine substitution in a highly conserved region of the metalloproteinase ADAMTS10. Western blotting revealed ADAMTS10 protein is preferentially expressed in the trabecular meshwork, supporting an effect of the variant specific to aqueous humor outflow. The Gly661Arg variant in ADAMTS10 found in the POAG Beagles suggests that altered processing of extracellular matrix and/or defects in microfibril structure or function may be involved in raising intraocular pressure, offering specific biochemical targets for future research and treatment strategies.

Highlights

Elevated intraocular pressure is a strong risk factor for glaucoma development and progression [1]
We have found a variant in ADAMTS10 that belongs to a family of genes that contribute to formation of extracellular matrix and may itself be involved in formation of elastic microfiber structures
By application of the zygosity criterion, linkage and haplotype analyses, we were able to map the Beagle Primary open angle glaucoma (POAG) locus to a single 4 Mb region on chromosome 20. This canine POAG locus is syntenic with a region on human chromosome 19 within a quantitative trait locus for regulation of intraocular pressure identified by a genome-wide scan of 486 families [13]

Summary

Introduction

Elevated intraocular pressure is a strong risk factor for glaucoma development and progression [1]. In POAG, increased resistance to outflow of aqueous humor through the trabecular meshwork is the cause of elevated intraocular pressure [2]. The only proven treatments for POAG patients involve reduction of intraocular pressure by inhibiting aqueous humor production, or bypassing the diseased trabecular meshwork. The mechanisms of increased resistance to aqueous humor outflow are not wellunderstood [2], but may involve changes in extracellular matrix composition of the trabecular meshwork [3]. Linkage studies have identified a number of POAG loci [4]. Genome-wide association studies could be a powerful tool to establish more POAG loci, this requires recruitment of a large number of patients. We have used a canine model to identify a candidate POAG gene, which has the advantage of availability of tissues from normal and affected dogs as well as future gene rescue experiments to investigate the pathogenic mechanisms of the gene variant

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Conclusion