Study finds large proportion of intellectual disability is not genetically inherited

New research published Online First in The Lancet suggests that a high proportion of severe intellectual disability results from genetic causes that are not inherited. These findings are good news for parents, indicating a low risk of passing on the disorder to further children.

affects between 1% and 2% of children worldwide. Although a handful of genes that appear to cause some cases of intellectual disability have been identified, the of the disorder in most people remains unclear, especially those with non-syndromic types which have no obvious physical signs and cause up to 50% of intellectual disability worldwide.

Some evidence suggests that de novo (new) , that show up for the first time in affected children but are not found in their parents, might be a common cause of the disorder.

As a joint effort by the German Network led by André Reis from the Institute of Human Genetics, University of Erlangen-Nuremberg, Germany, the current study used a new technique known as exome sequencing to look for mutations that are not inherited but newly formed in 51 children with unexplained severe non-syndromic intellectual disability (an IQ <50) and their unaffected parents from nine centres across Germany and one center from Switzerland.

The researchers found that children with intellectual disability carried a significantly higher number of likely disease-causing mutations in their genome than those without the disorder. New mutations in both 11 known and six new were estimated to cause intellectual disability in up to 55% of the cases studied.

"Although believed to be relatively common in intellectual disability, these results suggest that only a small proportion of cases of sporadic intellectual disability are likely to be inherited in autosomal recessive fashion (affected children inherit one copy of the faulty from each parent)", explains Reis.

Writing in a linked Comment, Jozef Gecz and Eric Haan from the University of Adelaide in Australia point out, "Copy number variant profiling and whole-exome sequencing should resolve most (>60%) cases of severe intellectual disability. The remaining cases might be more complex, with contributions from multiple genes, environmental factors, or mutations in non-coding regions of the genome. Whole-genome sequencing technology has the potential to become the first-line diagnostic test for many disorders, and particularly intellectual disability."

More information: www.thelancet.com/journals/lan… (12)61480-9/abstract

Related Stories

New gene for intellectual disability discovered

Jul 15, 2011

A gene linked to intellectual disability was found in a study involving the Centre for Addiction and Mental Health (CAMH) – a discovery that was greatly accelerated by international collaboration and new genetic sequencing ...

New form of intellectual disability discovered

Apr 27, 2012

Researchers at the Centre for Addiction and Mental Health (CAMH) led a study discovering a gene for a new form of intellectual disability, as well as how it likely affects cognitive development by disrupting neuron functioning.

Recommended for you

A nucleotide change could initiate fragile X syndrome

22 hours ago

Researchers reveal how the alteration of a single nucleotide—the basic building block of DNA—could initiate fragile X syndrome, the most common inherited form of intellectual disability. The study appears ...

Gene clues to glaucoma risk

Aug 31, 2014

Scientists on Sunday said they had identified six genetic variants linked to glaucoma, a discovery that should help earlier diagnosis and better treatment for this often-debilitating eye disease.

Mutation disables innate immune system

Aug 29, 2014

A Ludwig Maximilian University of Munich team has shown that defects in the JAGN1 gene inhibit the function of a specific type of white blood cells, and account for a rare congenital immune deficiency that ...

Study identifies genetic change in autism-related gene

Aug 28, 2014

A new study from Bradley Hospital has identified a genetic change in a recently identified autism-associated gene, which may provide further insight into the causes of autism. The study, now published online in the Journal of ...

NIH issues finalized policy on genomic data sharing

Aug 27, 2014

The National Institutes of Health has issued a final NIH Genomic Data Sharing (GDS) policy to promote data sharing as a way to speed the translation of data into knowledge, products and procedures that improve health while ...

User comments