Tuesday, March 24, 2009

Single Alzheimer’s Gene Protects People, Double Gene Does Harm

Single Alzheimer’s Gene Protects People, Double Gene Does Harm

By Elizabeth Lopatto

March 12 (Bloomberg) -- One copy of the mutant gene A673V, and a person is protected from Alzheimer’s disease. Two copies, and he or she is guaranteed to get it.

A group led by a researcher in Italy came to that conclusion after finding a man who was diagnosed with early-onset dementia at age 36. His sister has mild cognitive impairment, according to a study published in the journal Science. The scientists said both siblings had two copies of the A673V gene. Six of their relatives aged 21 to 88 had one copy of the mutation each, and didn’t have Alzheimer’s.
Alzheimer’s is most likely caused by beta amyloid, which clumps in the brain, choking neurons, Snyder said. Beta amyloid is created when another substance, amyloid precursor protein, is snipped in two places by enzymes.

After discovering the man and his sister, scientists led by Fabrizio Tagliavini of the Carlo Besta National Neurological Institute, in Milan, cultured cells from the patients who had no copies, one copy or two copies of the A673V mutation and studied how the genes affected live proteins.

Lab experiments showed that more beta amyloid proteins were created by the cells with two copies of the mutation, and the beta amyloid was also more likely to clump together. Cells with one copy of mutated A673V produced less beta amyloid clumps than those with no copies, the experiments showed.

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