Nine genes linked to learning disabilities

CAMBRIDGE, England, April 20 (UPI) -- An international team of more than 70 researchers says it has found nine new genes on the X chromosome that, when knocked-out, lead to learning disabilities.

The scientists said they studied nearly all X chromosome genes in 208 families with learning disabilities. The researchers said they also discovered approximately 1 percent of X chromosome genes, when knocked-out, have no apparent effect on an individual's ability to function in the ordinary world.

Estimates suggest the prevalence of learning disability is significantly more common in males than in females. The scientists said genetic causes have long been sought on the X chromosome -- males have only one X chromosome and so a gene mutation on the X is more likely to have an effect in males than in females.

"We sequenced 720 out of the approximately 800 known genes on the X chromosome in more than 200 families affected by X-linked learning disabilities," said Professor Mike Stratton, from England's Wellcome Trust Sanger Institute. "This is the largest sequencing study of complex disease ever reported."

The research that included scientists from the United States, Australia, Spain, South Africa, the Netherlands, Belgium, France and Germany is reported in the journal Nature Genetics.