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Three new gene variants linked to late-onset Alzheimer's disease

7 September 2009
Appeared in BioNews 524

British and French researchers have this week announced the discovery of three new genes linked to late-onset Alzheimer's disease, certain variations in which may increase a person's risk of developing the disease by 10-15 per cent. If new drugs could be developed to counter the effects of these mutations, it could help to prevent 20 per cent - the equivalent of 100,000 cases - of Alzheimer's disease in the UK per year, the researchers claim.

Two of the genes discovered - CLU, which produces clusterin, and CR1, which produces complement receptor 1 - have been shown to help prevent the build-up of 'plaques', comprising mostly of amyloid beta peptide, in the brains of Alzheimer's patients. The other gene, known as PICALM, produces a protein involved in the functioning of synapses - the connections between nerves - which are known to be involved in the formation of memories.

Inflammation of the brain is one of the key symptoms of Alzheimer's disease and previously this was thought to be triggered by the build up of plaques. However, this latest research suggests that the absence of functional CLU and CR1 proteins may be the primary cause, as both have been implicated in the regulation of immune response. The researchers have questioned whether common anti-inflammatory drugs, such as aspirin and ibuprofen, could be used to reduce Alzheimer's disease risk in patients who carry certain variants in these genes.

Julie Williams, Professor of Psychological Medicine at Cardiff University and chief scientific advisor to the Alzheimer's Research Trust, who led the British study, told the Times newspaper: 'If we can combat the detrimental effects of these two genes, we estimate it could reduce the chances of people developing Alzheimer's by almost 20 per cent. This research is changing our understanding of what might cause the common form of Alzheimer's disease and could provide valuable new leads in the race to find treatments.'

The British-led study involved scanning the genomes of 16,000 patients, 4,000 of which had Alzheimer's, each for a total of 500,000 gene variants, making it the largest of its kind conducted on Alzheimer's disease patients to date. The French-led study similarly looked at DNA samples from more than 14,000 affected and unaffected patients.

Alzheimer's disease is a progressive neurodegenerative disorder, characterised by loss of memory and personality changes, which eventually lead to death. Late-onset Alzheimer's is the most common form of the disease, and approximately 700,000 people in the UK are affected by it. APOEe4, which was discovered 15 years ago, is the only other gene variant linked to 'common' late-onset Alzheimer's disease.

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