NEW YORK (GenomeWeb News) – A new mutation detected in dachshunds is providing insights into the genetics behind a group of devastating eye diseases.
In a paper appearing online in Genome Research last night, investigators from Norway, Sweden, and the US used genome-wide studies of just over a dozen dachshund sibling pairs to identify a new mutation linked to eye diseases called cone-rod dystrophy. The mutation, in a gene called NPHP4, is helping researchers pinpoint the molecular changes underlying some forms of the eye disease and, they say, may ultimately lead to new therapies.
“This gene has been associated with a combination of kidney and eye disease in human patients,” co-senior author Frode Lingaas, a researcher at the Norwegian School of Veterinary Science, said in a statement. “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.”
Cone-rod dystrophy refers to a set of degenerative eye disorders in which the retina loses photoreceptor cells over time. Because these cells help the eye detect bright light, photoreceptor degeneration eventually leads to a condition known as “dayblindness.” It can also result in total blindness in the long run. So far, though, just a handful of cone-rod dystrophy genes have been discovered in humans.
Although inherited eye disorders are fairly common in dogs, only a few breeds — including miniature long-haired dachshunds, standard wire-haired dachshunds, and pit bull terriers — are prone to cone-rod dystrophies. And of these, genetic causes have only been detected for miniature long-haired dachshunds.
For the latest study, Lingaas and his colleagues used a genome-wide approach to look for canine mutations linked to cone-rod dystrophies in wire-haired dachshunds. By first comparing the genetics of affected and unaffected sibling dogs with canine SNP array-based sibling transmission disequilibrium test analysis, the team narrowed their search to a region on chromosome five containing more than 70 genes.
They then used resequencing and RT-PCR to identify the culprit mutation: a truncation in the nephronophthisis 4 or NPHP4 gene.
In the past, several NPHP4 mutations resulting in both kidney and eye disease have been detected in humans. But this is the first NPHP4 mutation shown to cause eye disease independent of kidney disease. That information may prove useful for those studying canine eye disease as well as researchers trying to get to the bottom of human cone-rod dystrophies.
“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,” co-senior author Kerstin Lindblad-Toh, a researcher affiliated with the Broad Institute and Uppsala University, said in a statement.