Epigenetics and the Health of Future Generations
By Dr. Janine A. Clayton
We typically learn in school how parents pass along their genes to their children, and how those genes can influence their children’s characteristics. Statements like — "She has her mother’s eyes" and "He has his father’s dimples" — are not uncommon.
Certain aspects of genetics, such as passing genes to future generations, are fairly straightforward and well known, at least generally. A less well-known concept is that of "epigenetics." Whereas genetics involves genes inherited from parents, grandparents, and so on, epigenetics concerns how changes in those genes can be generated by the environment, age, and lifestyle.
One can think of it this way: genetics concerns "which" genes a child gets while epigenetics concerns "changes" to those genes. Two siblings may have the same gene but due to epigenetics the gene might express one way in one child and a different way in the other.
The study of epigenetics is not new, but in the 1990s, David Barker, M.D., a British physician and epidemiologist, presented an interesting idea which at the time was controversial but now is widely accepted. He proposed that some chronic diseases, such as cancer and heart disease, are not always a result of purely genetics or an unhealthy lifestyle. Dr. Barker believed that the mother’s nutrition during pregnancy, and the exposure of children to infection after birth, could also contribute to certain conditions later in the child’s life.1
In the past, researchers have studied the growth and nutrition of children while in the mother’s belly as well as soon after birth, and how these factors might contribute to adult disease. Two important studies include those done in The Netherlands and China. During the Second World War, the Dutch experienced a famine. At the height of the famine, daily food rations were estimated to be less than 500 calories daily per person.2
Dutch researchers found that children carried by pregnant women during the famine were twice as likely to develop schizophrenia later in life when compared to children who were not exposed to the famine.2 A study of a Chinese famine that occurred in the 1950s found similar results.2 This showed a clear link between the health of the child during pregnancy and the risk of disease later in life.
A separate study funded by the National Institutes of Health and conducted by the University of Pennsylvania showed that the sex of the offspring – that is, whether the offspring is male or female – can also have an impact in epigenetics. The study involved adult rats, their ingestion of cocaine, and its effect on the memory of the offspring.
In this study male rats consumed cocaine prior to impregnating female rats. The research showed that only the male offspring of rats consuming cocaine had impaired long-term memory.3 The female offspring, as it turned out, did not have impaired memory even if the parent consumed cocaine.
Scientists also found that the brains of male mice offspring were different than those of the females. Certain brain regions in the male offspring where anatomically different due to the expression of genes that are important for memory formation.3
The Office of Research on Women’s Health (ORWH) supports research focusing on sex differences, including epigenetic research. An example of this is ORWH’s Specialized Centers of Research Excellence (SCORE) on Sex Differences which support established scientists across the country.
One such investigator supported is Tracy Bale, Ph.D., a researcher formerly with the University of Pennsylvania. As a professor of neuroscience, Dr. Bale focuses her research on the role of stress and disorders arising from the abnormal development of the brain at an early age.
Researchers like Dr. Bale are now exploring how epigenetic changes can affect future generations. For example, her research has shown that parental lifetime stress exposure in mice could cause epigenetic changes that are passed on to future generations and which may be a factor in making future generations vulnerable to PTSD.4
This and other types of research are important to better understand how epigenetic changes can affect future generations. ORWH supports epigenetic research because the results can help us both as a society and individuals to take action to reduce the susceptibility of individuals to a lifetime disease.
References
1. Cooper, C. (2013, September 11). David Barker Obituary. The Guardian. Retrieved from http://www.theguardian.com/society/2013/sep/11/david-barker
2. Brown, S.A. & Susser, E.S. (2008). Prenatal nutritional deficiency and risk of adult schizophrenia. Schizophrenia Bulletin, 30 (6):1055-1063. PMID: 18682377
3. Wimmer M.E., Briand L.A., Fant B., Guercio L.A., Arreola A.C., Schmidt H.D., … Pierce R.C. (2017). Paternal cocaine taking elicits epigenetic remodeling and memory deficits in male progeny. Molecular Psychiatry, 22. PMID: 28220045
4. Rodgers, A. & Bale, T. (2015). Germ cell origins of PTSD risk: The transgenerational Impact of parental stress experience. Biological Psychiatry 78(5): 307–314. PMID: 25895429