The Implications of Environment & Epigenetics on Reproductive Health
Vidita Shah
Epigenetics is an emerging field in modern biology. Epigenetics is the study of how behavior and environment can affect gene expression. Epigenetic changes can be contrasted to genetic mutations. Genetic changes are permanent and cannot be reversed naturally. On the other hand, rather than directly changing DNA, epigenetic modifications change what DNA is used and how much it is used. DNA, or the genetic information of a cell, provides the “recipe” or “blueprint” for a cell to make proteins. Proteins are composed of amino acids and are the machinery of cells [3]. Epigenetic changes impact the way proteins function and are produced.
There are three primary ways that epigenetic changes occur within a cell. The first method is DNA methylation. DNA methylation is one way that epigenetics works in cells. It involves placing small chemical tags on pieces of DNA. These tags, called methyl groups, prevent the cell from turning DNA into RNA; in other words, the cell can’t copy the “recipe” from the DNA The next method for changes to the epigenome is histone modification. Histones are large proteins that DNA is wrapped around. DNA can be wrapped around histones tightly or loosely. When loosely wrapped, DNA can be used to create the recipe for proteins. When tightly wrapped, DNA cannot be transcribed. One form of epigenetic modification is changing how tightly DNA is wrapped around a histone in order to control the transcription of proteins. The final method of epigenetics is the usage of non-coding RNA. Non-coding RNA is RNA that does not code for proteins. This non-coding RNA can attach to coding RNA and mark it for destruction [2].
Epigenetics can change a wide variety of factors related to reproductive health. The early environment a child experiences can have long term consequences for their future reproductive health. For example, women in northern and western countries have higher reproductive hormone levels than women in eastern and southern countries. The amount of reproductive hormones in women affects the age at which they undergo puberty. Another example of the environment affecting reproductive health can be found within comparisons between Bangladeshi migrants in the UK and Bangladeshis from Bangladesh. Girls that came to Bangladesh at a young age had earlier puberty, like their British neighbors, compared to Bangladeshi girls raised in Bangladesh who had later periods. Bangladeshi girls raised in Bangladesh were found to have shorter reproductive periods and lower hormone levels compared to Bangladeshi girls who were raised in the UK. The age of puberty has long-lasting effects on health and even predisposition for cancer [1]. The community in which a girl grows up in can have severe impacts on her future health. This environmental influence is known as epigenetics
The nutritional status of a mother can also have a strong impact on the health of her offspring. When an embryo is formed by the combination of the female’s egg and the male’s sperm, the epigenetic markers of the parents are not passed on to the embryo. However, as the embryo continues to develop, it accumulates many epigenetic markers that can affect its wellbeing later in its life. Mothers with poor nutrition change the DNA methylation pattern of the fetus they’re carrying [4]. Female offspring of nutritionally stressed mothers have a smaller pool of germ cells (future eggs) than their counterparts whose mothers were not struggling with their nutrition. Women whose mothers were malnourished did not ovulate as often, which can impact their fertility. In Bolivia, the Aymara community was found to have chronically low levels of progesterone due to nutritional stress [1]. The wellbeing of a mother can severely impact the reproductive wellbeing of the next generation.
Puberty and ovulation are just two examples of parts of reproductive health that can be affected by epigenetics. Epigenetics can influence fertility, lengthen the menstrual cycles of women, lower hormone levels, and more. Given that community and environment can have such a strong impact on the reproductive health of a person, it is important that physicians use this knowledge when considering how to treat individuals from different backgrounds [4]. Epigenetic changes make the effect of the environment on health explicit. Further research into epigenetic changes can allow for a better standard of reproductive care that is more personalized and more effective for patients from a variety of backgrounds.
References
Bar-Sadeh, B., Rudnizky, S., Pnueli, L., Bentley, G. R., Stöger, R., Kaplan, A., & Melamed, P. (2020). Unravelling the role of epigenetics in reproductive adaptations to early-Life Environment. Nature Reviews Endocrinology, 16(9), 519–533. https://doi.org/10.1038/s41574-020-0370-8
Centers for Disease Control and Prevention. (2022, August 15). What is epigenetics?. Centers for Disease Control and Prevention. https://www.cdc.gov/genomics/disease/epigenetics.htm#:~:text=Epigenetics%20is%20the%20study%20of,body%20reads%20a%20DNA%20sequence.
U.S. National Library of Medicine. (n.d.). What is epigenetics?: Medlineplus Genetics. MedlinePlus. https://medlineplus.gov/genetics/understanding/howgeneswork/epigenome/
Lifestyle Choices Influence Reproductive Health Through epigenetics. This is Epigenetics. (n.d.). https://thisisepigenetics.ca/about-epigenetics/lifestyle-choices-influence-reproductive-health-through-epigenetics