26 new genes linked to intellectual disability have been discovered by researchers from the Centre for Addiction and Mental Health (CAMH) and Queen’s University. The study, published in Molecular Psychiatry, studied the genomes of 192 families and uncovered mutations in 72 distinct genes thought to be linked to developmental disorders. Understanding the genetics behind the conditions has significant implications in diagnosis and care.

“This is the largest study of its kind on intellectual disability to come out of North America,” said Dr. John Vincent, team leader and head of the Molecular Neuropsychiatry and Development (MiND) Laboratory in the Campbell Family Mental Health Research Institute at CAMH.

More than 1 in 100 children are affected by intellectual disability worldwide, which is characterised by significant limitations in learning ability. The condition is similar to autism, and previous work has shown that the two share several disease-linked genes.

To better understand the genetic roots of intellectual disability, the team worked with 192 families from Pakistan and Iran who had more than one family member with the disability. The genes behind the condition are frequently recessive, meaning that both parents need to be carriers for a child to inherit it. As familial marriages are more common in South Asia, the Middle East, and Africa, families from these regions of the world offer a more concentrated selection of these recessive genes and make it easier for researchers to identify significant mutations.

“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,” said Dr. Vincent.

The team were able to locate and identify mutations in half of the families across 72 distinct genes. Of these, they identified 26 new genes alongside 11 that the team had previously uncovered.

On an immediate level, understanding what genes can contribute to intellectual disability opens up the possibility of screening prospective parents so that they can receive the necessary support. In future, however, it also may have implications in developing personalised treatments for patients depending on what mutations they carry. It is likely that there are hundreds of mutations governing the condition and so further work will be necessary before this is possible, but this research is an important step forwards.

“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,” said 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.”