Intellectual disability and genetics – A new research

genetics

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Intellectual disabilities caused by protein defect

September 4, 2017

Intellectual disabilities are often caused by a mutation that damages a gene, preventing the associated protein from functioning properly. However, a mutation can also change the function of a gene. As a result, the gene in question acts in a completely different way. Researchers from Radboudumc discovered this mechanism in fifteen genes playing a role in the development of intellectual disabilities. Their research results published in the American Journal of Human Genetics on 31 August 2017 show that these changes in function play a more prominent role than previously thought.

Genes are responsible for protein production in cells. A common cause of intellectual disabilities is a de novo mutation (i.e. a mutation present in a child, but not in its parents) damaging a gene so severely that it is no longer able to produce functional proteins. The resulting protein defect will cause illness. In a number of disease-related genes, it is shown that a de novo mutation does not eliminate the gene, but probably alters its function. These mutations are only located on specific parts of the gene.

Change in function

In order to find out how often this mechanism is involved, researchers from Radboudumc have combined the gene mutations in Dutch patients with a large international database comprising de novo mutations in patients. This research project was led by geneticist Christian Gilissen. « With our method, we were able to detect genes in which mutations not so much eliminate as affect the gene in another way. We found fifteen genes in which mutations cluster closely together, twelve of which being associated with developmental disorders. We also found three new genes that are likely to play a role in the development of intellectual disabilities as well », according to Gilissen.

Interactions

The de novo mutations that were found only change a very small part of a protein. The function of the protein remains largely, but not entirely the same. Gilissen says: « The mutations are more likely to affect superficial parts of the proteins. These disturb interactions with other proteins and cause problems. Although mutations eliminating genes were often thought to be the main cause of intellectual disabilities, mutations altering the function of genes are now shown to be an important factor as well. That is a surprising finding. »

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More information: Stefan H. Lelieveld et al. Spatial Clustering of de Novo Missense Mutations Identifies Candidate Neurodevelopmental Disorder-Associated Genes, The American Journal of Human Genetics (2017). DOI: 10.1016/j.ajhg.2017.08.004

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