A Prenatal Link to Alzheimer's?

New research at Genentech Inc. is challenging conventional thinking about Alzheimer's disease, providing a provocative theory about its cause and suggesting potential new targets for therapies to treat it.

The researchers propose that a normal process in which excess nerve cells and nerve fibers are pruned from the brain during prenatal development is somehow reactivated in the adult brain and "hijacked" to cause the death of such cells in Alzheimer's patients.

The dominant view of Alzheimer's disease today is that it is caused by deposits called beta amyloid that accumulate in the brain because of bad luck or other unknown reasons, degrading and destroying nerve cells and robbing victims of their memory.

The new findings offer evidence that "Alzheimer's is not just bad luck, but rather it is the activation of a pathway that is there for development purposes," says Marc Tessier-Lavigne, executive vice president, research drug discovery, at Genentech. "It suggests a different way of looking at Alzheimer's disease."

The report, being published Thursday in the journal Nature, is based on laboratory and mouse experiments, and further study is needed to validate the hypothesis.

Genentech, a South San Francisco, Calif., biotech company, says it has identified potential drug candidates based on the findings, but even if they prove promising, it would take several years for any potential treatment to be developed.

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