In the United States, more than 5.8 million people are living with Alzheimer’s disease (AD), a progressive neurological disorder that is the leading cause of dementia.
Scientists have found some genetic variations that make people more likely to get Alzheimer’s.
The AAPOE ε4 allele is the most well-known of these for people over the age of 65. Approximately 60% of patients with Alzheimer’s who are of European ancestry contain this genetic mutation, compared to just 26% of the general population, suggesting that additional genes may contribute to the genetic basis of the illness.
Researchers from the Boston University School of Medicine (BUSM) and the University of Chicago have found a new gene called MGMT that raises the risk of Alzheimer’s in women. The findings of this study were published this week in Alzheimer’s Disease & Dementia: The Journal of the Alzheimer’s Association.
Using several techniques, the researchers carried out a genome-wide association study (GWAS) for Alzheimer’s in two separate datasets.
One strategy centered on dementia in a sizable extended family of Hutterites, a pioneering group with central European ancestry who arrived in the country’s mid-west. Because Hutterites live in small, isolated communities, their gene pool is small, which makes it easy to study how genes affect the disease. All of the study’s Alzheimer’s patients were female.
Based on evidence that Alzheimer’s and breast cancer are linked, the second method looked at genetic information from a national group of 10,340 women who didn’t have APOE ε4. In both sets of data, MGMT was strongly linked to developing AD.
According to Lindsay Farrer, PhD, director of biomedical genetics at BUSM and a senior author of the study, “this is one of a few and perhaps the strongest associations of a genetic risk factor for Alzheimer’s that is specific to women.”
The author adds: “This finding is particularly robust because it was discovered independently in two distinct populations using different approaches. While the finding in the large dataset was most pronounced in women who don’t have APOE ε4, the Hutterite sample was too small to evaluate this pattern with any certainty.”
Then, the researchers looked at MGMT in more depth using different kinds of molecular data and other AD-related traits found in human brain tissue.
After a lot of research, they found that epigenetically regulated gene expression (one of the ways cells control gene activity without changing the DNA sequence) of MGMT, which helps fix DNA damage, is strongly linked to the development of amyloid-β and tau, two proteins that are characteristic of Alzheimer’s disease, especially in women.
The study’s main author, Carole Ober, PhD, chair of human genetics at the University of Chicago, remarked, their findings underline “the value of founder populations for genetic mapping studies of diseases like Alzheimer’s.”
“The relatively uniform environment and reduced genetic variation in Hutterites increases our power to find associations in smaller sample sizes than required for studies in the general population. The validation of our findings in the larger dataset used by the Boston University group was enormously gratifying and ultimately led to supportive epigenetic mechanisms that connected both sets of GWAS results to the MGMT gene.”
The researchers claim that this study highlights the value of looking for genetic risk factors for AD that can be gender-specific. To fully understand why MGMT increases AD risk more in women than in males, more research is required.
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