"As well as these important new gene discoveries relating to learning disability, we have also uncovered a small proportion - 1% or more - of X chromosome protein-coding genes that, when knocked out, appear to have no effect on the characteristics of the individual," explains Mike Stratton. "It is remarkable that so many protein-coding genes can be lost without any apparent effect on an individual's normal existence - this is a surprising result and further research will be necessary in this area."
This finding will also act as a warning to geneticists. Large-scale studies are designed to uncover associations between knocked-out genes and disease. However, this study shows that a small proportion of gene knock-outs have no discernable effect on the individual. In future studies, researchers must therefore be cautious about assuming that the presence of a knocked out gene in an individual with a particular disease means that the knocked out gene is causing the disease.
The research comes towards the end of a long process of gene cataloguing in this field. Scientists believe that there are likely to be more undiscovered genes that contribute to X-linked learning disabilities; however, variants at what are expected to be lower frequency will become increasingly difficult and costly to uncover. The next challenge is to implement this improved knowledge of the complex of genes that lead to learning disabilities in clinical practice.
"We already offer genetic counselling to families with X-linked learning disabilities," says Dr Lucy Raymond, Reader in Neurogenetics, Cambridge Institute for Medical Research at the University of Cambridge. "This new research uncovers yet more genes th
|Contact: Don Powell|
Wellcome Trust Sanger Institute