Tuesday, January 16, 2007

Gene linked to Alzheimer’s identified

BruneiDirect.com: Scientists said on Sunday they have pinpointed a new gene linked to Alzheimer’s disease, the incurable brain disorder that is the top cause of dementia in the elderly.

Abnormalities in a gene called SORL1 increased the risk for the disease, and this finding could help scientists develop new treatments, the researchers reported in the journal Nature Genetics.

The researchers looked at DNA samples from 6,000 people from four ethnic groups: Caribbean-Hispanics, North Europeans, black Americans and Israeli-Arabs. They found certain variations of SORL1 more often in people with late-onset Alzheimer's disease than in healthy people.

The late-onset form, affecting people age 65 and up, represents about 90 percent of Alzheimer's cases. The rarer early-onset form affects people from about age 30 to 65.

Only one other gene, called ApoE4, has been identified as a risk factor for late-onset Alzheimer's. It was identified in 1993.

Several genes are linked with early Alzheimer's, and study of both types might lead to better understanding of how the disease begins and how to tackle it.

Many scientists think Alzheimer's begins with the buildup in the brain of a gooey material called amyloid that clumps together to form plaques. That material stems from a protein called amyloid precursor protein, or APP.

SORL1 controls the distribution of APP inside nerve cells of the brain. When working normally, the gene prevents APP from being degraded into a toxic byproduct called amyloid beta peptide. When SORL1 is deficient, it allows more of the bad amyloid beta peptide to accumulate, fostering amyloid plaques.

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