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Alzheimer’s genes identified

alz graph.bmpThree new genes associated with Alzheimer’s have been discovered, to the delight of researchers in the field.

In two papers published in Nature Genetics, two teams describe how they compared the genomes of sufferers to healthy controls to identify potential gene variations leading to the disease. Philippe Amouyel’s team identified variants within CLU and CR1, while Julie Williams and her team also identified CLU and added PICALM to the mix.

“If we were able to remove the detrimental effects of these genes through treatments, we could reduce the proportion of people developing Alzheimer’s by 20%,” Williams, of Cardiff University in Wales, told a press conference. “In the UK alone this would prevent just under 100,000 people developing the disease. So the significance of these results in truly meaningful.”

Amouyel’s group used a genome-wide association study, comparing 2,032 French citizens with Alzheimer’s and 5,328 controls. Williams used 3,941 cases and 7,848 controls. Her team also confirmed the association of the disease with apolipoprotein E (APOE), the most important link to Alzheimer’s yet discovered.

To date, four genes have been definitively associated with Alzheimer’s, write Williams et al, but only APOE has been linked with the most common form. Amouyel’s paper notes:

Twin studies suggest that genes may have a role in more than 60% of Alzheimer’s disease susceptibility and that APOE may account for as much as 50% of this genetic susceptibility. More than 550 other genes have been proposed as candidates for Alzheimer’s disease susceptibility, but thus far none have been confirmed to have a role in Alzheimer’s disease pathogenesis.

APOE’s role was discovered in the early 90s, leading these papers to be hailed as “the most significant such discovery in 15 years” and “a leap forward for dementia research”.

Writing in the Independent, Neil Hunt, chief executive of the Alzheimer’s Society, says, “It is not very often that scientists are prepared to stick their necks out and refer to research results as a ‘breakthrough’. This is one of those very rare occasions when it is a word that really does fit the bill.”

Image: Scatter-plot from Williams paper with chromosomal position on the x axis and the statistical significance of the genome-wide association study on the y axis. The red line shows the threshold for significance, above which are APOE, CLU, and PICALM.


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