Seven Genes Causing X-linked Intellectual Disability Identified

An international research team headed by Vera Kalscheuer, Max Planck Institute for Molecular Genetics in Berlin has analysed 405 families, in which cases of X-linked intellectual disability occur. Defective genes on the X chromosome //cause X-linked intellectual disability. The disease is passed on in a recessive manner in men, as they possess only one X chromosome.

Women are affected only if both their X chromosomes carry the defective genes. Women with one healthy and one mutated X chromosome have a 50 percent chance of passing the mutated X chromosome on to their offspring.

The search for the responsible genetic defect was very tedious due to the high variability of the clinical picture.

Researchers have discovered changes in a number of genes that were already related to the disorder and mutations in seven other genes that were not associated with the disorder.

High-throughput sequencing allows sequencing of a large number of DNA segments simultaneously and identifies genetic defects. Scientists investigated all DNA regions of the X chromosome containing protein-relevant information.

"In addition to known disease-related genes, we have discovered seven novel genes as the cause of X-linked intellectual disability and analysed what signalling pathways in the cells each protein is involved in," said Kalscheuer.

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The clinical presentation and severity of the disorder depend on the responsible gene and the nature of the mutation. With the help of systematic re-sequencing of all X-linked genes, the responsible genetic defect can be identified in around 60 percent of families with X-linked intellectual disability.

Source-Medindia