 October 20, 2011 - A Foundation-funded researcher team led by the University of Pennsylvania has discovered a canine retinal disease with an amazing, unexpected effect. While the condition, called ERD for “early retinal degeneration,” acts like a typical retinal disease and causes the loss of photoreceptors, it also leads to the proliferation of new ones. Though this research effort is still at an early stage, it might provide important clues into how the retina could be manipulated — perhaps with a biological treatment or gene therapy — to generate new photoreceptors for overcoming vision loss from a variety of retinal diseases.The discovery is both novel and surprising, because in humans and most other mammals, photoreceptor cells stop dividing shortly after birth. Normally, if these cells are lost to injury or disease, the retina can’t generate new ones and vision is lost. The investigative team discovered the phenomenon of new photoreceptor generation while studying ERD in dogs of the Norwegian Elkhound breed. They were initially puzzled because vision loss in the affected dogs plateaued. Microscopic analyses revealed that photoreceptors were being replaced as quickly as they were dying. The new photoreceptors were identified as hybrid rod-cones. (Rods normally provide peripheral and night vision. Cones provide central and daytime vision.) The researchers are working to determine exactly what vision the new hybrid photoreceptors are providing. Dr. Gus Aguirre, the lead investigator on the project, says that the major task ahead is to better understand the function of the gene linked to ERD known as STK38L. “We really need to find out what this gene is doing, and how it does it. There are several hypotheses we are testing and investigating. The most logical one is that it is involved in controlling cell division in a mature retina. Ultimately, our aim is to see if we can tweak the system to keep producing more cells to replace the dying ones,” he says. The research effort was also conducted by Drs. William Beltran, a former Foundation Career Development Award recipient, Agnes Berta, and Sem Genini, all of whom are with the University of Pennsylvania School of Veterinary Medicine, along with Dr. Kathleen Boesze-Battaglia of the Penn School of Dental Medicine and researchers from Cornell, the National Eye Institute, and Semmelweis University of Medicine in Hungary. Results of the study were published online in the open access journal Public Library of Science One on September 30, 2011.
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