APP Gene and Alzheimer’s

Animal models have been an invaluable resource for the study of human disease.  For Alzheimer’s disease, some common animals used to study the disease have been rats, mice, rabbits, and even fruit flies. Neurological diseases are a tricky bunch, however, and require researchers to think of creative ways to recreate the disease in an animal model.

Alzheimer’s disease has been especially challenging. Even one of our closest primate relatives, the chimpanzee, doesn’t decline with age like we do and has given us very little insight into the disease. Other models have proven what we already believed—that if we don’t get in front of this disease, it appears almost impossible to stop. In other words, we need to understand what causes Alzheimer’s, learn more about the risk factors involved, and come up more effective ways to diagnose it before symptoms show up.

Predicting the disease has proven to be equally perplexing. Reports have come up with about anything you can think of as being associated with a greater risk of Alzheimer’s disease, but no one thing has proven gold.

The good news: with the invention of genomic sequencing, researchers have been able to directly investigate human genetic biomarkers associated with Alzheimer’s, or, in the upcoming case, the lack thereof. Research released this week in Nature, to me, marks a solid step forward in the fight for our old age. Maybe we don’t have the entire picture on how Alzheimer’s develops, but scientists from the Icelandic company DeCODE think they may have found a gene that prevents it. A rare mutation in the gene APP, coined A673T, appears to prevent not only Alzheimer’s but also general age-related cognitive decline. In the study, people with this gene never developed Alzheimer’s.

This storyline of dementia-free people sounded vaguely familiar to me somehow, so I did a little more research into where this nostalgia was coming from. In the early 1990’s, Dr. Staffan Lindeberg and his team examined a population of indigenous people on the island of Kitava, Papua New Guinea. There he found a society of people which he claims were dementia-free. Lindeberg didn’t have the fancy imaging machines we have today, devices that can detect amyloid plaques, therefore definitive diagnosis would have been impossible. Lindeberg’s team proposed the Kitavan’s diet may have contributed to their dementia-free old age. But what if these individuals are carrying the rare APP mutation A673T? If I worked for DeCODE, I’d be sending some of my team to take some blood samples immediately.

–Elizabeth Weaver

Sources:

Brain Shrinkage: It's Only Human. Study Finds Chimpanzees, Our Closest Animal Kin, Aren't Affected by the Oddity of Aging; 'We Are Very Weird Animals'. Wall Street Journal. HEALTH INDUSTRY July 26, 2011. Robert Lee Hotz

Aging of the cerebral cortex differs between humans and chimpanzees. Chet C. Sherwooda, Adam D. Gordon, John S. Allen, Kimberley A. Phillips, Joseph M. Erwina, Patrick R. Hoff, and William D. Hopkins. PNAS. 2011.

The Kitava Study. Staffan Lindeberg.

A mutation in APP protects against Alzheimer’s disease and age-related cognitive decline. Thorlakur Jonsson et al. Nature. 2012.

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