Quebec family key to discovery of blindness disease gene

Researchers at the MUHC have discovered a new gene for retinitis pigmentosa (RP) – a group of inherited diseases that result in degeneration of the eye’s retina. Patients suffer gradual vision loss – often described as like seeing the world through a rolled up newspaper – which results in complete blindness in as little as 6 months. The new discovery published in the journal Human Genetics this month was achieved thanks to the involvement of a family in Quebec, where genetic diseases are often more prevalent than in other parts of the world. This discovery provides a greater understanding of RP, facilitating prenatal, preclinical and carrier testing and advancing the development of treatments and cures for the 1.5 million sufferers of this disease worldwide.

“This study is a perfect example of how clinical practice and basic research combine to facilitate discovery and improve health care-one of the great benefits of academic health centres like the MUHC,” says Dr. Koenekoop, Director of the McGill Ocular Genetics Centre, and one of the principal researchers of the new study. The research, which involved collaboration with Dr. Shomi Bhattacharya at the Molecular Genetic Division of The Institute of Ophthalmology in the United Kingdom, began five years ago with the establishment of the McGill Ocular Genetics Centre at the MUHC. “The family members that became part of our study were patients at our clinic,” says Dr. Koenekoop. “Using a genetic technique known as linkage exclusion, we were able to exclude the currently known genes of RP and with further linkage studies, we were able to isolate this new gene from genetic samples of the family members.”

Quebec is the perfect place to study genetic diseases like RP; the Quebec population – numbering approximately 6 million – is known as a founder population, which can be traced back to around only 250 forefathers; as a result this small gene pool provides the ideal population for the study of genetic disease. “Genetic diseases like RP are more common in founder populations,” says Dr. Koenekoop. “Our patients are enthusiastic to participate in these studies, knowing that this research may ultimately lead to improved treatments and cures.”

This new gene discovery brings the total number of genes associated with retinitis pigmentosa to over 30. Scientists estimate there may be another 40-50 genes associated with this disease still left to discover, making this one of the most complex human conditions in the world. “Each gene discovery is vital because it highlights a disease pathway, which provides yet another way for us to help patients,” notes Dr. Koenekoop. Although scientists have only identified around half the genes they believe may be involved in RP, this has not hindered the development of cutting-edge treatments, with human clinical trails already underway.

This study was funded by The Foundation Fighting Blindness Canada.

The McGill University Health Centre is a comprehensive academic health institution with an international reputation for excellence in clinical programs, research and teaching. The MUHC is a merger of five teaching hospitals affiliated with the Faculty of Medicine at McGill University–the Montreal Children’s, Montreal General, Royal Victoria, and Montreal Neurological Hospitals, as well as the Montreal Chest Institute. Building on the tradition of medical leadership of the founding hospitals, the goal of the MUHC is to provide patient care based on the most advanced knowledge in the health care field, and to contribute to the development of new knowledge.