London, Feb 15 (IANS): Researchers have identified seven new genes that can cause X-linked intellectual disability, a disorder that predominantly affects men and can have highly variable clinical manifestations.

Mutations of these genes on the X chromosome lead to various forms of intellectual disability, the researchers noted.

"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 Vera Kalscheuer from the Max Planck Institute for Molecular Genetics in Berlin, Germany.

According to the scientists, the proteins associated with the newly discovered genes may also be involved in epilepsy, autism and schizophrenia.

The researchers analysed 405 families, in which cases of X-linked intellectual disability occur.

As males only have one X chromosome and the disease is passed on in a recessive manner, the disorder mainly occurs in boys.

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

Because of the high variability of the clinical picture, the search for the responsible genetic defect was, until a few years ago, very tedious.

For some years now, scientists have been aided in their research of genetic diseases by high-throughput sequencing. This technology allows to sequence a large number of DNA segments simultaneously and to more easily identify genetic defects.

Using this method, the scientists investigated all DNA regions of the X chromosome containing protein-relevant information.

The study appeared in the journal Molecular Psychiatry.