Researchers Identify Gene Most Often Responsible For Commonest Form Of Congenital Blindness

Eye Health Month is off to an exciting start, with the recent announcement by MUHC researcher Dr. Robert Koenekoop and his colleagues of a breakthrough discovery in the genetics of childhood blindness. The new study identified the gene most often responsible for LCA (Leber Congenital Amaurosis), the commonest form of congenital blindness.

"This discovery represents a significant advance in the fight against this debilitating condition." says Dr. Koenekoop, Director of the McGill Ocular Genetics Centre at the MUHC and Associate Professor in Ophthalmology, Human Genetics at McGill University. He is also principal co-investigator of this study with Dr. Anneke den Hollander, and Dr. Frans Cremers from The University of Nijmegen in the Netherlands.

LCA causes blindness from birth or during the first few months of life. About 600 patients with LCA are currently being diagnosed and managed at the McGill Ocular Genetics Center of the MUHC, directed by Dr. Koenekoop. The disorder affects 1 in 30,000 newborns, and is currently incurable. "This is about to change, however," says Dr. Koenekoop. "Our discovery has major implications for improved screening. It also opens avenues for treatment of LCA."

Discovery of the CEP290 gene and a single mutation found in 20 percent of LCA patients will significantly speed up the genetic testing process for blind children. From a therapeutic viewpoint, this discovery adds another pathway for possible therapeutic manipulation and paves the way for a human gene replacement trial of a related LCA gene (RPE65) in early 2007. If this trial is successful, gene replacement therapy may not be far off.

Prior to Dr. Koenekoop's discovery, LCA had been linked to mutations in eight genes. Together, these mutations account for about 45 percent of cases. By studying members of a Quebec family affected by LCA, Dr. Koenekoop's team, which includes research associate and molecular biologist Dr. Irma Lopez, was able to identify a mutation in a gene known as CEP290. This mutation was detected in 21 percent of unrelated cases - making it one of the most common causes of LCA yet identified. The team's research, which was funded by the Foundation Fighting Blindness Canada, was published in the September 2006 issue of The American Journal of Human Genetics.

"The Foundation Fighting Blindness is dedicated to funding the best research in Canada and Dr. Koenekoop's new gene discovery proves that," says Sharon Colle, National Executive Director. "We believe that childhood blindness is intolerable and that cures really are in sight." The MUHC, in collaboration with Dr. Anneke den Hollander and Dr. Frans Cremers from the University of Nijmegen, will continue research into LCA, conducting functional studies of the CEP290 gene and screening more patients for CEP290 mutations.

Quebec is the perfect place to study genetic diseases like LCA. Quebec's population of approximately 6 million is known as a "founder population" because it can be traced back to a small number (approximately 250) of forefathers. This small gene pool provides the ideal population for the study of genetic disease. "Genetic diseases like LCA are more common in founder populations," says Dr. Koenekoop. "Our patients are enthusiastic about participating in these studies. They realize this research may ultimately lead to improved diagnosis, treatments and cures."

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