Alzheimer’s and Offspring Part 2

Writer: Prahalad Srinivasan

Editors: Brianna Viets and Vijaya Varadarajan

Hello, and welcome to part 2 of our blog examining how Alzheimer’s could be passed onto offspring, where we are aiming to answer the question many Alzheimer’s patients have about whether or not their children will inherit the condition. If you missed part 1 of this blog and would like to catch up, click the following link to access it.

Last week, we established that there are 2 major contributing factors to the passing down of Alzheimer’s: lifestyle factors and genetic factors. There, we dove deeper into lifestyle factors that could influence the passing down of Alzheimer’s to offspring, specifically highlighting how maintaining a healthy diet and exercise routine is crucial in ensuring that one does not experience the condition. We understood that this forms an indirect connection with the passing down of the disease, as these lifestyle factors are often influenced strongly by parents. 

This week, we will examine the second of the contributing factors, genetics. This will help us understand the more direct inheritance patterns of Alzheimer’s, specifically how the passing of specific genes increases the probability of offspring having Alzheimer’s in their lifetime. 

Genetics of Alzheimer’s

As many of you already know, Alzheimer’s is not a genetic disease; it is not directly inherited and rather develops in people throughout their lifetime through buildups in the brain. However, this does not mean that genetic influences do not play a role in Alzheimer’s. Human beings have over 20,000 genes, each of which is influential in different ways. However, Alzheimer’s cannot be traced back to one specific gene. Rather, over 80 unique genetic areas could potentially influence the development of Alzheimer’s. Variations in these genes could increase (or decrease) the likelihood of a patient developing the condition in their lifetime. One such gene is the apolipoprotein E (APOE) gene, which is responsible for making a protein used to carry fats throughout the body. The APOE gene can be expressed in 1 of 3 alleles: APOE ε2, APOE ε3, and APOE ε4. Each person inherits 1 allele from each parent. Each allele’s effect on Alzheimer’s development is listed below:

APOE ε2: provides some amount of protection against Alzheimer’s, meaning patients with this allele would typically be diagnosed with Alzheimer’s late in their life if they ever are diagnosed with the condition

APOE ε3: has a neutral effect on the disease and is the most common allele

APOE ε4: highly increases the risk of Alzheiemer’s, and could lead to the development of the condition much earlier than expected

Inheriting 2 APOE ε4 alleles from your parents could significantly increase your chances of developing Alzheimer’s in your lifetime. However, this inheritance pattern is relatively rare, with only about 2-5% of people having both alleles. Also, inheritance of this combination does not guarantee that one will develop Alzheimer’s. Rather, it can be inferred that they have a higher chance of developing the condition, with researchers proving that having APOE ε4 alleles is linked with Alzheimer’s. Along with the APOE gene, many other genes could also affect Alzheimer’s development, such as mutations on chromosomes 21, 14, and 1. These could also increase the risk of Alzheimer’s, but researchers have identified the APOE gene as the most impactful in terms of developing the condition. 

Figure 1: An illustration of the 4 alleles of the APOE gene

Conclusion

Now that we understand the driving factors in passing down Alzheimer’s to offspring, we can finally develop an answer to the initial question posed. If you develop Alzheimer’s, it does not mean that your children will also develop the condition. However, based on lifestyle and genetic factors, there is a chance that they are at a greater risk for Alzheimer’s.  

Works Cited: 

“Alzheimer’s Disease Genetics Fact Sheet.” National Institute on Aging, U.S. Department of Health and Human Services, www.nia.nih.gov/health/genetics-and-family-history/alzheimers-disease-genetics-fact-sheet. Accessed 17 Dec. 2023. 

“Genetics by the Numbers.” National Institute of General Medical Sciences, U.S. Department of Health and Human Services, www.nigms.nih.gov/education/Inside-Life-Science/Pages/Genetics-by-the-Numbers.aspx#:~:text=20%2c000 Text=That's%20the%20 approximate%20number%20of,on%20how%20to%20make%20 proteins. Accessed 17 Dec. 2023. 

“Alzheimer Disease Stratified by Apoe Genotype.” Labmedica.Com, LabMedica International, 27 June 2019, www.labmedica.com/molecular-diagnostics/articles/294778461/alzheimer-disease-stratified-by-apoe-genotype.html.