Discovery of a new retinal gene involved in childhood blindness

Montreal March 2nd, 2009 – The team of Dr. Robert Koenekoop which includes Dr. Irma Lopez from the Research Institute of the MUHC at the Montreal Children's Hospital played a crucial role in the international collaboration that led to the discovery of a new gene that causes Leber congenital amaurosis (LCA) and retinitis pigmentosa (RP), two devastating forms of childhood blindness.

This finding of this new gene, called SPATA7, is remarkable because it identifies a new retinal metabolic disease pathway that may be crucial for many patients. It also opens a new avenue for a potential genetic therapy. Gene therapy targeting different genes has recently proved successful for the same disease in human subjects. The study will be published on March 5th, 2009 in the American Journal of Human Genetics.

Researchers have now identified a total of fifteen genes involved in LCA, but SPATA7 is the first gene with a mutation that disrupts the protein transport between two important compartments of the cell: the endoplasmic reticulum and the Golgi apparatus. All proteins in every cell have to pass through this transport pathway; thus SPATA7 plays a major role and its mutation may affect many aspects of vision.

"Until now we were not aware that this cellular mechanism played a role in LCA or any other eye disease. This is a very important step that opens up a number of new research avenues, particularly in our understanding of the specific cellular processes involved in blindness. This finding also increases the number of potential therapeutic targets and therefore the chances of finding a treatment. We are extremely motivated by all of these new possibilities," explained Dr. Koenekoop.

"This is an incredible discovery that gives great hope to LCA patients and their families, that gene based therapies can and will be developed to restore sight," said Sharon Colle, President and CEO of The Foundation Fighting Blindness, the leading private charity for vision research. "We are proud to fund such important discoveries involving prominent Canadian researchers and institutions."

A careful assessment of patients with some specific genetic types of LCA also demonstrated that their retinal cells (specifically the rod and cone photoreceptors), although not functional for vision, were still present and in relatively good condition. This critical observation will allow researchers to continue on the path towards gene therapies. Therapies targeting different genes for the same disease have already shown success in the United Kingdom and in the US, meaning that LCA patients can now enjoy hope for the future.

SPATA7 was identified using an innovative technology developed in the different laboratories involved in this international collaboration. "We started this protocol about two years ago, and it has already helped us to identify four new genes associated with LCA and RP before we discovered SPATA7," explained Dr Koenekoop.

The technique is based on DNA-chips and involves three steps: first the genetic material of the patient is screened to find mutations in 14 specific LCA and RP genes. The LCA and RP patients that are negative for this detailed screen are then subjected to a second DNA chip, this one to identify significant stretches of homozygosity in SNP markers. SNPs are single nucleotide repeats, which are natural variations in the human genome. These homozygous regions may contain new genes and are carefully probed based on functional information and then subjected to sequencing. "This method is indeed both very powerful and very promising for the future," said Dr. Koenekoop.

The Canadian component of this project was funded by The Foundation Fighting Blindness Canada (FFB) and by the Fonds de la recherche en santé du Québec (FRSQ).

Dr. Robert Koenekoop is the Director of the Division of Pediatric Ophthalmology and the McGill Ocular Genetics Laboratory at the Montreal Children's Hospital of the MUHC. He is a researcher in medical genetics and genomics with the Research Institute at the Montreal Children's Hospital of the MUHC. Dr. Koenekoop is also an Associate Professor in Human Genetics and Ophthalmology in the Faculty of Medicine at McGill University.

This project is a collaboration between the laboratory of Dr. Robert Koenekoop at the Research Institute of the MUHC at the Montreal Children's Hospital; the laboratory of Dr. Rui Chen, Texas Children's Hospital, Baylor College of Medicine, Houston; and the laboratory of Dr. Anneke den Hollander, the Nijmegen Centre for Molecular Life Sciences, Radboud University Nijmegen, in The Netherlands. The DNA chips were developed in collaboration with Dr. Rando Allikmets of Columbia University.

When the embargo will be lifted, find this press release, with the original article and a short audio document by following this link : http://www.muhc.ca/media/news/

The Research Institute of the McGill University Health Centre (RI MUHC) is a world-renowned biomedical and health-care hospital research centre. Located in Montreal, Quebec, the institute is the research arm of the MUHC, the university health center affiliated with the Faculty of Medicine at McGill University. The institute supports over 600 researchers, nearly 1200 graduate and post-doctoral students and operates more than 300 laboratories devoted to a broad spectrum of fundamental and clinical research. The Research Institute operates at the forefront of knowledge, innovation and technology and is inextricably linked to the clinical programs of the MUHC, ensuring that patients benefit directly from the latest research-based knowledge.

The Research Institute of the MUHC is supported in part by the Fonds de la recherche en santé du Québec.

For further details visit: www.muhc.ca/research.

The Montreal Children's Hospital (MCH) is the pediatric teaching hospital of the McGill University Health Centre and is affiliated with McGill University. The MCH is a leader in providing a broad spectrum of highly specialized care to newborns, children, and adolescents from across Quebec. Our areas of medical expertise include programs in brain development/behaviour, cardiovascular sciences, critical care, medical genetics and oncology, tertiary medical and surgical services, and trauma care. Fully bilingual, the hospital also promotes multiculturalism and serves an increasingly diverse community in more than 50 languages. The Montreal Children's Hospital sets itself apart with its team approach to innovative patient care. Our health professionals and staff are dedicated to ensuring children and their families receive exceptional health care in a friendly and supportive environment.