Currently, only a few genes are linked with human CRD, but there still exists other unidentified genes associated with CRD.
Eye disorders are one of the most frequently inherited disorders in dogs, however canine CRD is limited to only a few breeds.
In this study, scientists led by Dr. Frode Lingaas of the Norwegian School of Veterinary Science and Dr. Kerstin Lindblad-Toh of the Broad Institute of MIT and Harvard have identified a mutation in a novel gene for early-onset CRD in standard wire-haired dachshund by genome-wide association mapping of a dachshund family.
This genome-wide strategy isolated a region on chromosome 5 associated with CRD in dachshund. A search for mutations of this area revealed that a portion of the nephronophthisis 4 (NPHP4) gene has been deleted, which may be responsible for recessively inherited CRD in the standard wire-haired dachshund.
This finding may hold importance, as the human form of NPHP4 has been previously implicated in disease.
"This gene has been associated with a combination of kidney and eye disease in human patients. Here, we found a mutation that affects only the eyes, suggesting that this gene might be a candidate for human patients with eye disease only," explained Lingaas.
It was suggested that the protein coded for by the mutant form of NPHP4 may lack a domain that would normally interact with other proteins involved in eye function, yet still retain the region involved in kidney function.
"The new information that the NPHP4 gene can be involved in eye diseases only can shed light on the etiology of some low-frequency eye diseases in people where similar mutations may be involved," said Lindblad-Toh.
They found that identification of causal mutations for diseases has practical implications for dogs, as genetic tests could be implemented to avoid new cases of the disorder and reduce the frequency of the mutation in the population.
The study is published online in Genome Research.