Adapted from University of British Columbia

Researchers at the University of British Columbia and Vancouver Coastal Health Research Institute have discovered that the genetic mechanism which destroys brain cells is responsible for early development of Alzheimer's Disease in people with Down Syndrome and for development of Alzheimer's Disease in general population—providing a potential new target for drugs that could forestall dementia in people with either condition.

The research, led by Dr. Weihong Song, Canada Research Chair in Alzheimer's Disease and a professor of psychiatry in the UBC Faculty of Medicine, found that excessive production of a protein, called Regulator of Calcineurin 1 (RCAN1), sets in motion a chain reaction that kills neurons in the hippocampus and cortex in people with Down Syndrome and Alzheimer's Disease. The findings were published online recently in the Journal of Biological Chemistry.

"Neuronal death is the primary reason for the memory loss and other cognitive impairments of Alzheimer's Disease, and it's the main reason people with Down Syndrome develop Alzheimer's Disease long before most people, usually in their 30s," says Song, a member of the Brain Research Centre at UBC and the Vancouver Coastal Health Research Institute (VCHRI), and Director of Townsend Family Laboratories at UBC. "By looking for the common elements of both conditions, we were able to pinpoint how and why the deterioration occurs."

People with Down Syndrome have an extra copy of the gene that produces RCAN1, thus leading to its excess production. The resulting neuronal death—with symptoms that mirror those of AD patients—is one of the prime reasons for the shortened lifespan of people with DS.

The research team discovered that some AD patients have similarly elevated levels of the RCAN1 protein, despite having two copies of the responsible gene. It's still unknown why, though Dr. Song speculates that the gene's overexpression might be triggered by stroke, hypertension or the presence of a neurotoxic protein, called beta amyloid, which typically collects into clumps in the brains of people with AD—what he describes as a "vicious cycle" in which one destructive factor exacerbates another. But now that the culprit gene and protein have been identified, "we can develop therapies that interfere with the gene's ability to produce that protein, and hopefully short-circuit the destruction of brain cells," Dr. Song says.

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