A German shepherd with vision loss may play a key role in finding a cure for human achromatopsia, a rare form of color blindness. Achromatopsia is an inherited disorder affecting roughly 1 in 33,000 people in the U.S. As it's currently understood, the rare condition is triggered by abnormalities in the retina, that thin layer of tissue at the back of the eye containing light-sensitive cells. People with the disorder experience a partial or total loss of the color portion of their vision as well as sensitivity to light. According to statistics, the eventuality of total loss is more common than partial loss. At present, there is no cure for achromatopsia, but researchers are hoping a recent discovery concerning a German shepherd whose owners were concerned about its vision will pave the way for a new understanding concerning humans with the condition and possibly a cure.
Researchers from Temple University in Philadelphia, PA, and the University of Pennsylvania are now studying the use of gene therapy using animal models as a promising path for curing achromatopsia in both humans and dogs. But they didn't pull the idea out of thin air. They actually stumbled upon the direction for the study by trying to uncover the underlying cause of the shepherd's loss of cone vision. It seems the animal couldn't see well during daylight hours but seemed to have no problem navigating in dimly lit conditions. These are apparently classic signs for the loss of cone vision. The researchers in connection to the diagnosis immediately began to try to identify the genetic cause of the dog's deteriorating eyesight, but they were unable to find any of the known gene mutations that lead to achromatopsia in canines.
Genetic Mutations in Animals & Humans
Through analyzation of five genetic mutations recognized for playing a role in how light signals are transmitted from the eye to the brain, the group was able to identify a mutation in a gene known as CNGA3 found to be responsible for the shepherd's loss of vision. The next step was studying Labrador retrievers observed with similar symptoms as the German shepherd. This investigation led to the team being able to identify a different mutation on the same area of the CNGA3 gene where the shepherd's mutation had been found. They noted in the results of their study that these mutations have never been seen before in canines, but the particular gene mutation found in the shepherd has been seen in human beings. All of this brings attention to the helpfulness of dogs as worthwhile models for studying the condition of achromatopsia in humans.
The next step was adopting a supercomputer technique that gave the team the opportunity to recognize minor changes in protein sequences that could ultimately have vital significance for visual signaling. From all of this the researchers were able to gather that the two mutations discovered in the CNGA3 gene of canines marred the function of the cyclic nucleotide channel, a major player in the role of converting visual signals. These new findings provide fresh insights into the molecular mechanisms underlying the condition of achromatopsia and highlight the possibility that gene therapy could be the eventual cure for the condition in both humans and dogs. Senior author of the study Karina Guziewicz was recently noted as saying, "Everything we found suggests that gene therapy will be the best approach to treating this disease, and we are looking forward to taking that next step."
For a complete review of the study, interested readers can find it published on PLOS ONE.