Gene responsible for Leber Congenital Amaurosis

Jun 5 2007

A MUHC-led study identifies a gene responsible for Leber Congenital Amaurosis (LCA), the most common cause of congenital blindness in infants and small children.

The study, partly funded by the Foundation Fighting Blindness in Canada (FFB-C), is published in Nature Genetics.

"This discovery has the potential to fast-track a cure for this disease," says lead investigator Dr. Robert Koenekoop, director of the McGill Ocular Genetics Centre at the MUHC. "Our main research goal is to identify all the genes responsible for congenital blindness in children and then study them so that we can then use gene therapy to rescue their vision."

Working with an international team of researchers including Drs. Anneke den Hollander, Frans Cremers and Ronald Roepman from the University of Nijmegen in The Netherlands, and Dr. Chris Inglehearn from The University of Leeds in the UK, Dr. Koenekoop and his team, including Dr. Irma Lopez, used a new technique called SNP (single nucleotide polymorphism) technology to identify homozygous regions in the genome, which led to the discovery of the new gene called LCA5. In the past, large families were necessary to find genes, but in this study only samples from one Quebec and one American patient were used to accomplish this. The SNP micro array technology accelerated the process of locating the gene and enabled the investigators to isolate it within a few months instead of several years. "This method may become a model for identifying other retinal diseases and causes of blindness in the future," says Dr. Koenekoop, who is also associate professor in Ophthalmology and Human Genetics at McGill University.

The same international research team identified the CEP290 gene last year, the most common genetic cause of LCA (American Journal of Human Genetics September, 2006). By using the protein structure of CEP290, the investigators were able to discover LCA5, as they have similar structures and functions in the retina. Both the CEP290 and LCA5 genes encode proteins with vital functions in the cilium of the photoreceptors, transporting visual proteins to the compartment where vision occurs. When these genes are mutated, which occurs in about 25 to 30 per cent of blind children, the visual proteins are not transported properly to the outer segments, causing the photoreceptors to stop working and die.

This year, after many years of research on a related LCA gene called RPE65 and a spectacular rescue of vision by RPE65 gene replacement in dogs with LCA, human clinical trials have started in London, UK and in Philadelphia, USA. "Preliminary results have been very encouraging and we expect to launch clinical trials investigating gene replacement for CEP290 and LCA5 in the near future," says Dr. Koenekoop.

An estimated 200,000 children worldwide are afflicted with LCA.

The FRSQ, the TD FINANCIAL GROUP and The Foundation Fighting Blindness in Canada (FFB-C) funded this research. "Discoveries like this one show us that treatments and cures are in sight. The Foundation Fighting Blindness in Canada is proud to fund quality vision research at the MUCH that is giving hope to families affected by blindness," says Sharon Colle, National Executive Director of the FFB-C.