Night blindness found in dogs for first time

Dogs too can get afflicted with a form of night blindness seen in humans, researchers including one of Indian-origin have found for the first time, a discovery that may lead to a gene therapy for the disorder.
People with congenital stationary night blindness, or CSNB, have normal vision during the day but find it difficult or impossible to distinguish objects in low light.
Researchers have for the first time found a form of CSNB in dogs.
The discovery and subsequent hunt for the genetic mutation responsible may one day allow for the development of gene therapy to correct the dysfunction in people as well as dogs, researchers said.

The team included the University of Pennsylvania School of Veterinary Medicine's Gautami Das, a postdoctoral researcher; Keiko Miyadera, an assistant professor of ophthalmology; and Gustavo Aguirre, professor of medical genetics and ophthalmology.
Their main collaborator was Mineo Kondo, a professor and chair of ophthalmology at Mie University Graduate School of Medicine in Tsu, Japan, from whom they found out about a unique population of beagles with night-vision problems.

The dogs had been bred by a Japanese pharmaceutical company and displayed behaviours characteristic of night blindness.
"In bright light they can walk around and navigate easily, but in darkness they sort of freeze," Aguirre said.

The company enlisted the expertise of Kondo's team, which confirmed that the condition was CSNB by using physiological measures of the dogs' retinal function.
All the affected dogs showed signs characteristic of CSNB, specifically a type known as Schubert-Bornschein complete CSNB, which is also seen in humans.
In this condition, there is a malfunction in the process by which signals are transmitted between the retina's photoreceptor cells and bipolar cells.
The Japanese researchers first evaluated the dogs' pedigree to determine how the condition was inherited and found it was an autosomal recessive disease; in other words, a dog needs two copies of the mutated gene in order to be affected.

This process also allowed the scientists to see which of the dogs was a carrier for the disease.
The gene responsible for these dogs' condition remains a mystery, but the researchers believe a genome-wide approach by means of whole-genome sequencing will narrow their hunt.
"It could be that the mutation is in a regulatory region of the unidentified gene, such as within an intron or the promoter," Das said.
Once they find it, they can begin development of a gene therapy approach to treating the condition, a strategy found successful by Aguirre's group multiple times in dogs. This could find application in humans as well.

The study was published in the journal PLOS ONE.