In the conclusions raised by this study, the mutation of the PMS2 gene would cause a defect in the repair of DNA, which significantly increases the possibility of contracting colorectal cancer, a syndrome which is subsequently transmitted from generation to generation.
Thanks to the Balsac population file, set up by the UQAC in the 1970s, and the Cartagene research platform, the researchers determined that the source of the genetic variation would come from a single ancestor arrived in New France, almost 300 years ago.
Unfortunately, we do not know the identity or history of the colonist in question, since the names of the people registered in the Cartagene platform remains anonymous.
“Cronician geneticists will discover still unknown variants who find themselves, among other things, in discomfort involved in the repair of DNA. Often, these changes will find themselves in a family, or two, without being found elsewhere. This founder variant, arrived early in the colonization of Quebec, found itself at a frequency quite high to wonder if we were doing screening, “said the professor at McGill University and expert in population genetics, Dr. Simon Gravel.
According to the latter, around one Quebecer of French Canadian origin out of 800 would carry this transfer today. Certain sectors of Quebec, such as Charlevoix, La Côte-de-Beaupré, Saguenay-Lac-Saint-Jean, Beauce and Côte-du-Sud, have a really higher frequency. In the region, this figure climbs to 2.6 people in 1000 (or 1 in 385).
“In western Quebec, we find very little, less than 1 in 1000. So, between Charlevoix and Abitibi-Témiscamingue, we almost speak of a ten-factor”
— Simon Gravel, expert in population genetics
To date, this genetic variation associated with hereditary cancer is the most frequent identified in the French Canadian population of Quebec.
Quick and affordable screening
Crucial for effective treatment and complete remission, screening could greatly benefit from this scientific and medical advance. For example, a resident of a region with a high frequency of mutation in the PMS2 gene could go to the hospital and doctors would not have to dissect the entire genome, but just the gene in question.
“The fact that a pathogenic variation is also frequent in the French Canadian population suggests that a large-scale genetic screening could be carried out at low cost. By combining this discovery with other founding variations identified in specific populations in Quebec, it would be possible to detect a high risk for around 50 % of hereditary forms of current cancer using a simple test targeting a dozen variations, “said the clinician-researcher at the Research Institute of the McGill University Center, Dr William Foulkes.
For his part, Dr. Simon Gravel wants more people to be able to register for a database like that of Cartagene, which currently brings together 43,000 people aged 40 to 69.
“The more we have, the more questions we can answer and help clinicians in their diagnoses. We would like to extend the cohort to get regions that have a smaller sample. For example, we know the mutations that affect Saguenay-Lac-Saint-Jean, because our sampling is high, ”he justifies.