Scientists discover more genetic disorders in the Saguenay region of Quebec

Josianne Leblanc, left, and Luigi Bouchard were part of the local health authority team that analyzed data to identify the prevalence of 12 rare diseases in the Saguenay-Lac-Saint-Jean region.  (Myriam Gauthier/Radio-Canada - photo credit)

Josianne Leblanc, left, and Luigi Bouchard were part of the local health authority team that analyzed data to identify the prevalence of 12 rare diseases in the Saguenay-Lac-Saint-Jean region. (Myriam Gauthier/Radio-Canada – photo credit)

Quebec’s Saguenay is known for its rugged wilderness, scenic fjords and a people who pride themselves on their deep roots in the region.

But this population has also been a fascinating study for scientists, as it has remained geographically isolated since the 1830s.

Diseases considered rare worldwide are emerging with alarming frequency sagueneens. And now a team of local scientists has uncovered even more anomalies that could be affecting people’s health.

Marie-Jacqueline Thomas, a genetic consultant who works for the local health department, is among the team that noticed the unusual genetic mutations when compiling the data.

By combing through data from over 23,000 people who have opted for genetic screening over the past 12 years, the researchers discovered unusual genetic mutations that they had never seen before.

“Our team was able to identify these 12 disorders that are more common than we expected because they are rare genetic disorders. That’s how it all started,” said Thomas.

Thanks to a team of genetic counselors in the region, the data of thousands of people have been studied in depth and information on the prevalence of diseases on the ground has been provided.

The results of their research led the team to identify five never-before-identified diseases in the region. The results of these findings were published this month in the Journal of Medical Genetics.

From genes that can cause congenital hearing loss to genes that can cause deadly diseases, they found that a high proportion of people in the region are carriers of 12 rare diseases.

“We worked harder to identify the carrier frequencies. But that has taken years and years and years, and I would even say genetic counselors in Saguenay started these databases 20 years ago…”[It’s a] really great feeling for our entire team to be making these clinical observations,” said Thomas.

She says now that genetic researchers are aware of the broader trends, they can do better pre-emptive testing and raise awareness in the region.

Myriam Gauthier/Radio Canada

Myriam Gauthier/Radio Canada

General lack of genetic diversity

Thomas says some of these diseases have high carrier frequencies.

For example, a genetic condition that causes congenital hearing loss occurred in one in 32 people — a significant percentage, Thomas says.

Some of the 12 diseases are more common than others.

“They’re all extremely different. The only thing I could say is they’re really all the same how they’re inherited,” said Thomas.

“They are all autosomal recessive, meaning that for there to be an increased risk of having a child affected by the disease, both parents must be carriers of the disease.” So that’s really what connects them.”

“If you have a geographically isolated population in Saguenay that had huge families and many children, those children could be more likely to be carriers of these diseases.”

The “founder effect”

Luigi Bouchard, Co-Chairman of the Rresearch genetique et parcours de vie en santé Program says this relates to a concept called the “founder effect.”

“There were a few thousand founders in the region… in some waves of migration. And it’s really just a coincidence that when these founders decided to migrate, they were carriers of certain rare diseases, including the diseases we’re talking about today,” Bouchard said.

Thomas says these small groups have their own kind of “genetic baggage”.

“You know, we could certainly trace a common ancestor between maybe two people back 10 generations, but that’s not a blood relationship. It’s not a close relationship,” Thomas said, adding that among those who tested them for these genes, many didn’t have ties to the same family.

Radio Canada

Radio Canada

Information could help verify families

Because testing has changed so much over the past few decades, Thomas says that discovering patterns in genetic mutations has become even more common and accessible.

“We would really like to… raise awareness in the medical community in our region and in Quebec as a whole because three other conditions may not be fatal but have important implications for medical monitoring and treatment as early as childhood,” Thomas said.

Thomas said it’s important that these new diseases are added to current testing programs so that carrier couples can make informed decisions.


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