Down syndrome: two genes crucial
Some of the symptoms relating to Down syndrome have been linked to two genes on chromosome 21, a study on mice has shown.
People with Down syndrome carry an extra copy of chromosome 21. But it has been unclear which genes within this chromosome are responsible for the disorder, which includes mental retardation, early onset Alzheimer's disease and other health problems.
The Olig1 and Olig2 genes were found to be over-expressed in GM mice with a form of Down syndrome. Ts65Dn mice carry additional copies of some genes similar to those found on human chromosome 21. To uncover the effects of the two genes, scientists made them both less active. Reduced activity of the genes in mice corrected neurological problems such as abnormal brain activity.
It is likely that other genes are also involved, but having identified them it may be possible to inhibit them using gene therapy, thereby alleviating Down syndrome health problems. An earlier mouse study suggested that the extra copy of chromosome 21 protects against cancer. Using targeted gene therapies to tackle mental retardation would avoid a potentially difficult trade-off.