Message: Charlie Fidelman, Canwest News Service
Published: Thursday, December 04, 2008
MONTREAL - Canadian researchers have announced the discovery of a new illness called Mednik syndrome, a rare and debilitating genetic disorder unique to French Canadians.
So far only eight people have been identified with the mutation, and half of them died before age two, said neurologist Patrick Cossette of the University of Montreal Hospital Centre's Research Centre.
"It's a severe and debilitating illness," Cossette said, adding that the oldest patient with Mednik is now 15.
Mednik syndrome is attributed to common founders in the French Canadian population of Quebec who emigrated from France in between 1608 and 1759. Gene mutations in a small group such as Quebec's colonists could multiply easily.
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A research team led by Cossette discovered that the syndrome is caused by a newly found mutation in the AP1S1 gene. The gene is involved in the formation of the central nervous system and other organs.
"Our observations strongly suggest that Mednik syndrome is caused by impaired development of various neural networks, including the spinal chord, the inner ear, and possibly the brain," Cossette said. The finding was published Friday in the online version of Public Library of Science Journal PLoS Genetics.
The AP1S1 gene is responsible for transporting and sorting out proteins within the cells, Cossette explained.
Using genetic mapping and ascending genealogy, the mutation was traced to a group of families in Quebec from the Kamouraska region, in eastern Quebec, who share a common ancestor, Cossette said.
The mutation leads to severe mental retardation, red scaly skin patches, complete deafness, poor absorption of food in the gut and other problems.
Riviere-du-Loup dermatologist Christian Allen Drouin noticed several pediatric patients with skin lesions who also failed to develop normally, Cossette said.
The gene was mapped out at Genome Quebec, which promotes the research and development of genomics in the province. Two copies of the same recessive gene must be inherited to lead to the illness.
"Now that we know the gene, we can determine who is carrying it and avoid new cases of the syndrome," Cossette said, suggesting inhabitants of rural Kamouraska region be screened for the defect.
Researchers also knocked out the AP1S1 gene in zebra fish. In the animal model, the loss of the gene resulted in broad defects including severe motor deficits because the spinal cord was impaired, he said.
The discovery is expected to have implications beyond Mednik.
"It might be one piece of the puzzle in understanding deafness and mental retardation," Cossette said.
The disease is attributed to common founders in the French Canadian population of Quebec who emigrated from France in between 1608 and 1759.
Gene mutations in a small group such as Quebec's colonists could multiply easily.
Mednik is the latest of several "founder effect" disorders, including Tay-Sachs, identified among French Canadians.
Neuroscientists Eva and Fred Andermann of the Montreal Neurological Institute and Hospital, who were not involved in this study but have identified other recessive mutations in Quebec, said Cossette's discovery will be useful in identifying the mutation carriers.
"It's an interesting and unusual disorder," Fred Andermann said. "Advances in molecular biology has led to the identification of a lot of these disorders which were previously not recognized as entities, or were often mistaken as cerebral palsy or neonatal injuries."
SOURCE: http://www.canada.com/topics/bodyandhealth/story.html?id=1037068
© The Montreal Gazette 2008
