Scientists correct Fragile X in mice

Scientists have discovered a gene modification which helps to reduce some of the symptoms of Fragile X in mice - a condition which in humans is the leading inherited cause of autism and learning difficulties. Published in the journal Neuron, the research suggests that a new class of drugs entering human safety trials in America next year could help to reverse symptoms of Fragile X.

Professor Mark Bear, who led the study at the Picower Institute for Learning and Memory at Massachusetts Institute for Technology, is optimistic that the discovery will lead to new treatments in the future. 'These findings have major therapeutic implications for fragile X syndrome and autism', he said.

Fragile X is an incurable condition which affects one in 4000 boys and half as many girls and has been linked to learning difficulties, epilepsy, abnormal body growth and autism. The condition is caused by a mutation in the X chromosome's FMR1 gene which results in a weakening of the electrical signals sent along so-called dendric spines - connections involved in communication between brain cells - which become abnormally longer, thinner and more abundant.

Scientists believe that these brain abnormalities may be caused when, in the absence of the Fragile X Mental Retardation Protein (FMRP) - the protein encoded by the FMR1 gene - the production of another protein - mGluR5 - runs out of control. To test this theory, the researchers created 'double mutant' mice which were genetically modified to lack the FMR1 gene and also produce half the amount of mGluR5.

They found that many of the Fragile X symptoms, including some of the abnormalities in brain and body growth and development and epileptic seizures, were reduced in the double mutants when compared to 'single mutant' mice who lacked only the FMR1 gene. Although the researchers used a gene modification to reduce mGluR5, in theory the same thing could be achieved by a drug.

However Dr Mark Hirst, scientific advisor to the UK Fragile X Society, believes that reducing mGluR5 alone is unlikely be as effective on human Fragile X patients. 'We must not take our eye off the other proteins that are mis-regulated, as the basis of fragile X syndrome is likely to be more complex and involve other pathways', he told the BBC.