Gene Identified as Cause of Intellectual Disability Forms

Topic: Cognitive Disabilities
Author: Center for Addiction and Mental Health
Published: 2009/12/15 - Updated: 2022/08/11 - Peer-Reviewed: Yes
Contents: Summary - Definition - Introduction - Main Item - Related Topics

Synopsis: A gene involved in some forms of intellectual disability identified by scientists at Center for Addiction and Mental Health. Now that we have identified TRAPPC9 as a gene that may be associated with hundreds of thousands of cases of intellectual disability worldwide, we can build on that knowledge with research to help individuals and their families. Unlike intellectual disabilities that are part of a syndrome with other medical conditions or physical abnormalities, TRAPPC9 is associated with non-syndromic types of intellectual disability; these cause up to 50 percent of intellectual disabilities worldwide.

Defining Intellectual Disability (ID)

Intellectual Disability (ID)

Intellectual disability (ID) is a term used when a person has certain limitations in cognitive functioning and skills, including communication, social, and self-care skills. These limitations can cause a child to develop and learn more slowly or differently than a typically developing child. Intellectual disability can happen any time before a child turns 18, even before birth. According to the American Association of Intellectual and Developmental Disabilities, an individual has an intellectual disability if they meet three criteria:

IQ is below 70-75.
The condition manifests itself before the age of 18.
There are significant limitations in two or more adaptive areas (skills needed to live, work, and play in the community, such as communication or self-care).

Intellectual disability affects about 2-3% of the general population. Seventy-five to ninety percent of the affected people have a mild intellectual disability. Non-syndromic or idiopathic cases account for 30 to 50% of these cases. A genetic disorder causes about a quarter of cases, and about 5% of cases are inherited from a person's parents. Cases of unknown cause affect about 95 million people as of 2013.

Introduction

A gene involved in some forms of intellectual disability has been identified by scientists at the Center for Addiction and Mental Health (CAMH), as published this month in The American Journal of Human Genetics. The gene is called TRAPPC9. In the same journal two other international research teams independently confirm the findings of Dr. John B. Vincent, a scientist at CAMH, and his team.

Main Item

"This spotlights the intense interest that genetics is bringing to types of inherited intellectual disability that, to date, have been poorly understood," says Dr. Vincent.

"Now that we have identified TRAPPC9 as a gene that may be associated with hundreds of thousands of cases of intellectual disability worldwide, we can build on that knowledge with research to help individuals and their families," says Dr. Vincent.

May account for many cases of intellectual disability.

Unlike intellectual disabilities that are part of a syndrome with other medical conditions or physical abnormalities, TRAPPC9 is associated with non-syndromic types of intellectual disability; these cause up to 50 percent of intellectual disabilities worldwide.

"The discovery announced today sheds light on a gene for intellectual disability on one of the non-sex chromosomes," says Dr. Vincent, "just the seventh such gene that we know of."

The mutation in the TRAPPC9 gene identified by Dr. Vincent's team causes the production of a truncated protein version and results in faulty cell function.

Findings in Two Families

Because no highly recognizable physical differences are associated with non-syndromic intellectual disabilities, it is more difficult to tease out the genetic mutations that may cause them. But researchers and families have long suspected an inherited factor based on patterns observed in extended families. Families with many affected individuals, particularly families from cultures where cousin-cousin marriages are common, have become invaluable in searching for such genes. Recent technological advances make it possible to map disease-causing genes in a single family.

Dr. Vincent's team first identified and mapped out the TRAPPC9 gene in a large Pakistan family with at least seven members with non-syndromic intellectual disabilities.

"To date, most such genes have only been found responsible for disease in a single family," he adds.

But Dr. Vincent's team also found a mutation in the same gene in a family from Iran, confirming the gene's importance.

"This additional finding gives us a solid reason to continue to explore the gene and its possible mutations," he says.

Normal Brain Function

Future research may include studying how the gene is involved in normal brain function, studying genes with similar functions as candidate genes for intellectual disability, and devising potential therapeutic strategies. Dr. Vincent's team aims to provide scientists more clues to understand, diagnose, prevent, and treat intellectual disabilities.

Intellectual disabilities, also known as developmental delay or mental retardation, are a group of disorders defined by diminished cognitive and adaptive development. Affecting more males than females, they are diagnosed in between one and three percent of the population.

Study References:

The study, Identification of Mutations in TRAPPC9, which Encodes the NIK- and IKK-Beta-Binding Protein in Non-syndromic Autosomal-Recessive Mental Retardation, was funded by grants from the Ontario Ministry of Health and Long-Term Care and (US) NARSAD.

The Center for Addiction and Mental Health (CAMH) is Canada's largest mental health and addiction teaching hospital and one of the world's leading research centers in addiction and mental health. CAMH combines clinical care, research, education, policy development, and health promotion to transform the lives of people affected by mental health and addiction issues.

CAMH is fully affiliated with the University of Toronto and is a Pan American Health Organization/World Health Organization Collaborating Center.

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Attribution/Source(s):

This peer reviewed publication was selected for publishing by the editors of Disabled World due to its significant relevance to the disability community. Originally authored by Center for Addiction and Mental Health, and published on 2009/12/15 (Edit Update: 2022/08/11), the content may have been edited for style, clarity, or brevity. For further details or clarifications, Center for Addiction and Mental Health can be contacted at camh.ca. NOTE: Disabled World does not provide any warranties or endorsements related to this article.

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