Sep
21
2015

The video shows one of the dogs from the study with poor dim-light vision.    

If you have congenital stationary night blindness (CSNB), you’re virtually blind at night even though, by day, your sight is normal. A rare condition present from birth, CSNB affects not only humans but also, it appears, some canines.

Researchers at the University of Pennsylvania (Penn), working in collaboration with Japanese scientists, have discovered the first form of CSNB in a group of beagles. They have also begun the hunt for the genetic mutation responsible for the disease.

Their findings were published in PLOS ONE on September 14.

The beagles studied were bred by a Japanese pharmaceutical company and displayed behaviors characteristic of night blindness.

A research team led by Mineo Kondo, MD, PhD, a professor and chair of the Department of Ophthalmology at Mie University Graduate School of Medicine in Tsu, Japan, and the lead author, confirmed the condition as CSNB.

“They used a technique called electroretinography, which is what you would use as a diagnostic tool in human patients,” noted Keiko Miyadera, DVM, PhD, assistant professor of ophthalmology at Penn School of Veterinary Medicine (Penn Vet) and one of the paper’s authors.

“You flash a light and you can detect the signals coming from the photoreceptors and other cells of the retina. Doing that with different light intensities and different dark and light adaptation situations helps you nail down the particular condition the dogs have.”

All the affected dogs showed signs that were characteristic of CSNB, specifically a type known as Schubert-Bornschein complete CSNB, 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 researchers determined that the condition was an autosomal recessive disease and which dog was a carrier. They then ruled out 11 candidate genes and two other functionally relevant genes. They also found a pattern between affected, carrier and normal individuals.

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.

Video credit: Compliments of the University of Pennsylvania

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