Genetics of Alzheimer’s

As the number of Canadians with Alzheimer’s increases along with our aging population, the push is on for scientists to better understand this devastating condition and develop effective treatments for it.

While there is still much work to be done, some progress is being made in learning more about the genetics involved with this disease.

We now suspect there are multiple factors influencing the onset of Alzheimer’s Disease including both environmental and lifestyle components. Genetics also play a role in both early and late onset Alzheimer’s disease.

Early onset Alzheimer’s affects people between the ages of 30 and 60 and is responsible for less than five percent of all cases of the disease. This form of Alzheimer’s has a very strong genetic link – most cases are caused by an inherited change in one of three genes. Specific, single-gene mutations on chromosomes 21, 14 and 1 cause abnormal proteins to be formed and the disease progresses from there.

Researchers are working to study families with early-onset Alzheimer’s to observe brain changes that may occur before any symptoms appear. It is hoped we may gain insight.

In late-onset Alzheimer’s – by far the more common form – causes are not yet completely understood. We have yet to find a specific gene that directly causes this form of the disease, but there is one known gene that seems to be implicated – called apolipoprotein E (APOE) on chromosome 19. APOE comes in several forms and affects Alzheimer’s risk in different ways.

APOE2 is relatively rare and may have a protective effect against the disease. APOE3 is the most common variation and has a neutral effect on Alzheimer’s, neither increasing nor decreasing a person’s risk. Finally, APOE4 increases risk for Alzheimer’s disease.

A person can have zero, one or two APOE4 alleles. The more APOE4 alleles the person has, the higher their risk of developing Alzheimer’s.

While this is identified as a risk factor for the disease, it is not a guarantee - a person with APOE4 will not definitely develop Alzheimer’s.

Still, this is a promising start. We have identified one specific gene variant that is implicated in the most common form of Alzheimer’s. More research will undoubtedly lead to a better understanding of how this variant works in combination with other factors and could eventually be important in the development of an effective treatment.

APOE status can be determined by specific testing. At this time, it is not recommended except for research purposes.

At Okanagan Clinical Trials, we are currently participating in many Alzheimer’s studies some of which examine APOE4 and its role in the disease. For one such study we are looking for participants who are homozygous for the APOE4 allele. This means they have two copies of this allele and are therefore at a higher risk for the development of Alzheimer’s disease as they age. If you happen to know your APOE4 status because of previous genetic testing we would be very interested in having you participate in this research so please call us at 250-862-8141 and speak to one of our researchers.

 

 

 

 

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