Joubert Syndrome is a condition that affects brain development and manifests itself through delayed psychomotor development, abnormal coordination of eye movements and respiratory abnormalities. Since Dr. Marie Joubert and her colleagues described it for the first time in 1969, a number of related genes have been identified in various populations, but the causal gene of the Quebec form of the syndrome has remained until now unknown.
”No studies had been done to identify the genetic origin of the disease in Quebec, more specifically in the exact area of the Lower St. Lawrence where most cases in Quebec are concentrated,” Dr. Jacques Michaud, the study’s principal investigator, explained. “This is the first study to present a picture of Joubert syndrome in the Quebec population. It will allow family members affected by the syndrome to assess their children’s genetic risks with a simple DNA test.”
The finding is interesting, both genetically and historically, since, while Joubert Syndrome is present around the world, genetic strains can vary regionally. Distribution is related to the history of various population groups.
Quebec is no exception. In fact, 6,000 French Canadian settlers from Quebec City and its surroundings settled in the Lower St. Lawrence region about the end of the 17th and beginning of the 18th centuries. The fact that most present day inhabitants of the Lower St. Lawrence region descend from this small group of settlers suggests a genetic founder effects. Indeed, certain founder mutations are transmitted to a large number of descendants, which increases the risk of genetic diseases in offspring.
As a matter of fact, Dr. Michaud’s team identified three C5ORF42 mutations that are common to most of the families in the study. In all, seven families that are carriers of the gene were identified in a 400-km area along Route 132.
In the space of about two centuries, the first colonists settled in the Lower St. Lawrence region and from there other families headed out to settle along the river heading east as far as Mont-Joli and then along the Matapedia River. According to Myriam Srour, a doctoral student and co-author of the study, the mutations likely spread in the population along these migration routes.
So far 15 genes that play a role in the expression of the syndrome have been revealed elsewhere in the world. Dr. Michaud and his team will continue their research to better understand the exact function of the gene and the specific effect of each mutation.
About the study
The study was published in the April 6, 2012 edition of The American Journal of Human Genetics. It was made possible thanks to the Finding Rare Disorders Genes in Canada (FORGE Canada) consortium, funded by Genome Canada, the Canadian Institutes of Health Research, the Ontario Genomics Institute, Génome Québec and Genome British Columbia. Dr. Jacques Michaud holds a grant from the Fonds de recherche du Québec – Santé.
- Dr. Jacques Michaud’s Profile
- Sainte-Justine University Hospital’s Research Centre
- Centre of Excellence in Neuromics of Université de Montréal
About the CHU Sainte-Justine Research Center
The Sainte-Justine University Hospital Research Center is a leading mother-child research institution affiliated with the Université de Montréal. It brings together more than 1200 people, including over 200 researchers and 450 graduate and post-graduate students who carry out fundamental, clinical, translational, and evaluative research on mother and child health. Research work falls under six research axes, namely Health Outcomes; Brain Diseases; Musculoskeletal Diseases and Movement Sciences; Viral and Immune Disorders and Cancers; Fetomaternal and Neonatal Pathologies; and Metabolic Health. It is focused on finding innovative prevention means, faster and less invasive treatments, as well as personalized approaches to medicine. The Center is part of the Sainte-Justine University Hospital Centre, which is the largest mother-child centre in Canada and second most important in North America. www.chu-sainte-justine.org/research
Dr Jacques Michaud is available for interviews by appointment.
At the Sainte-Justine University Hospital’s Research Center
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