Abstract
Primary glaucoma is one of the most common causes of irreversible blindness both in humans and in dogs. Glaucoma is an optic neuropathy affecting the retinal ganglion cells and optic nerve, and elevated intraocular pressure is commonly associated with the disease. Glaucoma is broadly classified into primary open angle (POAG), primary closed angle (PCAG) and primary congenital glaucoma (PCG). Human glaucomas are genetically heterogeneous and multiple loci have been identified. Glaucoma affects several dog breeds but only three loci and one gene have been implicated so far. We have investigated the genetics of primary glaucoma in the Norwegian Elkhound (NE). We established a small pedigree around the affected NEs collected from Finland, US and UK and performed a genome-wide association study with 9 cases and 8 controls to map the glaucoma gene to 750 kb region on canine chromosome 20 (praw = 4.93×10−6, pgenome = 0.025). The associated region contains a previously identified glaucoma gene, ADAMTS10, which was subjected to mutation screening in the coding regions. A fully segregating missense mutation (p.A387T) in exon 9 was found in 14 cases and 572 unaffected NEs (pFisher = 3.5×10−27) with a high carrier frequency (25.3%). The mutation interrupts a highly conserved residue in the metalloprotease domain of ADAMTS10, likely affecting its functional capacity. Our study identifies the genetic cause of primary glaucoma in NEs and enables the development of a genetic test for breeding purposes. This study establishes also a new spontaneous canine model for glaucoma research to study the ADAMTS10 biology in optical neuropathy.
Highlights
Glaucoma is an optic neuropathy affecting the retinal ganglion cells and optic nerve
Human glaucomas form a heterogeneous group of diseases, which are broadly classified into primary open-angle (POAG), primary closed-angle (PCAG) and primary congenital glaucoma (PCG) [2]
A pedigree constructed around the affected dogs using GenoPro genealogy software suggested a recessive mode of inheritance as the affected dogs are born to unaffected parents and there are multiple affected littermates in some litters
Summary
Glaucoma is an optic neuropathy affecting the retinal ganglion cells and optic nerve. Human glaucomas form a heterogeneous group of diseases, which are broadly classified into primary open-angle (POAG), primary closed-angle (PCAG) and primary congenital glaucoma (PCG) [2]. In POAG, the iridocorneal angle (ICA) is open with an elevated IOP, which is considered as a significant risk factor for the disease. PCAG results from the collapse of the ICA structures, elevated IOP and subsequent death of the retinal cells [3]. Elevated IOP is caused by the blockage of the aqueous humor outflow due to a shallow anterior chamber combined with the obstruction of the iris-trabecular meshwork in the iridocorneal angle of the eye, [4]. PCG occurs within the first few years of life and is characterized by abnormalities in the anterior chamber angle and elevated IOP [4]
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