TORONTO, April 11, 2017 – Researchers at the Centre for Addiction
and Mental Health (CAMH) and Queen’s University have identified 26 new
genes linked to intellectual disability. Currently most patients with
intellectual disability receive no molecular diagnosis, which significantly
affects their health and shortens their lifespan.
The study, published online today in Molecular Psychiatry,
has implications for the diagnosis and clinical care of those affected, and
also adds to our growing knowledge of brain development and functioning. It may
eventually lead to personalized treatments for affected individuals.
Interestingly, some of the genes identified are thought to be connected with
autism spectrum disorders.
“This is the largest study of its kind on
intellectual disability to come out of North America,” said Dr. John Vincent, team leader and Senior Scientist who heads the MiND
(Molecular Neuropsychiatry and Development) Laboratory in the Campbell Family Mental Health Research Institute at CAMH. The study
was jointly led with Prof. Muhammad Ayub
of Queen’s University.
More than one in 100 children worldwide are affected by
intellectual disability, which is characterized by significant limitations in
learning that also affect their day-to-day lives. Frequently, intellectual disability
also accompanies symptoms of autism spectrum disorders, and many genes have
been found to be shared by the two illnesses.
The study involved 192 families from Pakistan and Iran with
more than one affected family member. Intellectual disability is
frequently caused by recessive genes, meaning that an affected child gets a
defective copy of the gene from each parent.
The families in the study all had a history of marriage
among relatives, which occurs quite commonly in communities in South Asia, the
Middle East and Africa. Studying families with this background, and multiple
affected individuals, can enable researchers to identify disease genes that
would otherwise remain hidden.
The Canadian research team pinpointed mutations related to
intellectual disability in half of these 192 families, in 72 different genes.
The identification of 26 new genes adds to 11 new genes that the team had
previously linked to intellectual disability.
diagnosis and care
One immediate implication of the study is to prevent future
cases of intellectual disability, the researchers note. Unaffected family
members and relatives could be genetically screened to see if they carry these
mutations, and provided with counselling on the risks of “within
A broader goal is to develop diagnostic screening tools that
are also relevant to populations in which “within family” marriages are
rare, such as Canada, USA, Japan, China and Europe. Ultimately, this information would be used to plan
more personalized treatment.
While 26 genes may seem a substantial number, there are
likely hundreds of genes that, when defective, may lead to intellectual
disability. “The strategy we have used speeds up the process of identifying
disease genes and of enabling diagnostic labs to deliver more accurate
information for clinicians and families,” says Dr. Vincent. This strategy
involves various genetic techniques, including microarray genotyping and whole
exome sequencing, and studying families with a history of marriage among
“There’s an opportunity now to further explore
the functioning and biological pathways of these genes, and to help complete
the picture of how the central nervous system works,” says Dr.
Vincent. “Knowing the genes involved is a big step forward, but
understanding how they function is also crucial before we can start planning
treatments or even cures.”
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for Addiction and Mental Health (CAMH) is Canada's largest mental health and
addiction teaching hospital and a world-leading research centre in this field.
CAMH combines clinical care, research, education, policy development and health
promotion to help transform the lives of people affected by mental illness and
addiction. CAMH is fully affiliated with the University of Toronto, and is a
Pan American Health Organization/World Health Organization Collaborating
Centre. For more information, please visit camh.ca or follow @CAMHnews on Twitter.
For more information,
Media Relations, CAMH
(416) 595-6015 / email@example.com