- Scientists have identified the genetic basis of a disease that causes intellectual disability, affecting around 1 in 20,000 young people.
- The disorder is characterised by symptoms such as short stature, microcephaly, seizures and reduced muscle mass.
- It is hoped that this discovery will facilitate the development of new diagnostic methods and provide answers for affected families.
Scientists have discovered the genetic cause of a disease that causes intellectual disability and is estimated to affect around 1 in 20,000 young people. They hope that their discovery will lead to new diagnoses and provide answers for families.
Patients with the disease suffer from a range of problems, including short stature, microcephaly, seizures and loss of muscle mass, the researchers said in their study published Friday in the journal Nature Medicine.
“We were surprised at how common this condition is” compared with other rare diseases linked to single genes, said Ernest Turo of the Icahn School of Medicine at Mount Sinai and lead author of the study.
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These syndromes can go unnoticed because their symptoms are sometimes so subtle that doctors can’t recognize them just by looking at the patient, said Dr. Charles Billington, a pediatric geneticist at the University of Minnesota who was not involved in the study.
This microscope image shows the 46 human chromosomes in blue, with telomeres as white dots. Scientists have discovered the genetic cause of a neurodevelopmental disorder that is estimated to affect 1 in 20,000 young people. (Hesed Padilla Nash, Thomas Reed/National Cancer Institute/National Institutes of Health via The Associated Press, File)
“So this wasn’t necessarily something that had a name,” he says, “and we’re learning more about these syndromes that can only be recognized once we know the cause.”
According to the researchers, the mutation occurred in a small “non-coding” gene — that is, a gene that doesn’t provide instructions for making a protein. To date, of the roughly 1,500 genes known to be associated with intellectual disability overall, all but nine are protein-coding genes. Most large-scale genetic studies to date have used sequencing techniques that filter out non-protein-coding genes.
The study used more comprehensive “whole genome” sequence data from 77,539 people who took part in the UK 100,000 Genomes Project, including 5,529 with intellectual disability. The researchers found that a rare variant in a gene called RNU4-2 was strongly associated with the likelihood of developing intellectual disability.
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The discovery “opens the door to diagnosis” for thousands of families, said study author Andrew Mumford, research director for the NHS Genomic Medicine Service in South West England.
More research is needed, Mumford said. It remains unclear how the mutation causes the disorder, and there is no cure. But Billington said labs should be able to offer tests for the disease relatively soon. And researchers should be able to help families find each other, support each other, and know they’re not alone.
“That’s incredibly comforting,” Mumford said.
