2.5) Epigenetics

Epigenetics is the study of how your behaviors and environment affect the way your genes function. Epigenetics literally means “above” or “on top of” genetics. It acts like switches that tell the genes to turn on or off, or to adjust like a dimmer up or down based on the signals received.

Unlike your DNA code which does not change, your epigenetics do change. It is the mechanism that affects how cells “read” the genes. They change how your body reads a DNA sequence and how the genes express themselves. 

This means that what you do impacts your DNA. The type of decisions you make about health and the way you choose to live your life directly determines health and impacts longevity. This is what makes the study of DNA so exciting. Your DNA code gives you a roadmap for your body. But your lifestyle steers the course.

Epigenetics involves changes that affect gene activity and expression. Effects on cellular and physiological traits may result from external or environmental factors or be part of normal development.

Each of your cells expresses, or turns on, only a fraction of its genes. The rest of the genes are repressed or turned off. Genes are turned on and off in different patterns during development to make a brain cell look and act different from a liver cell or a muscle cell, for example.

Gene regulation also allows cells to react to changes in their environments.

Figure 2-9 Identical twins have the same DNA code. External or environmental factors effect cellular and physiological traits.

Your actions change how your genes are expressed, your gene expression. The study of changes caused by modification of gene expression rather than alteration of the genetic code itself is called epigenetics. Your DNA code is your lifetime blueprint. How you live your life – the materials you use and the quality of craftmanship you employ – determine how that blueprint becomes your house – or rather your body. Diet, exercise, stress, sleep, environment, and more play an essential role in how your DNA is expressed.

Epigenetic changes can last generations

One of the most interesting and emerging discoveries is that epigenetic changes don’t stop with you. Epigenetic changes can be passed from one generation to the next, sometimes for several generations, without changing a single gene sequence.

Most epigenetic changes only occur within the course of one person’s lifetime; however, research is showing that epigenetic changes can be transmitted to offspring through transgenerational epigenetic inheritance. This means the health decisions you make may not only affect you, but may affect your children, your grandchildren and your great-grandchildren.

Mother’s diet affects the epigenome of children

A study observing genetic predispositions in children found that those born from an overweight mother were more likely to be epigenetically programmed to build unhealthy amounts of adipose tissue (Li et al., 2010). Additional findings showed that when mothers had poor diets, children were more likely to be overweight throughout their lifetime. A further study found that the maternal diet could alter the epigenome of children and modify disease susceptibilities. (Lillycrop & Burdge, 2015).

Studies like this show the importance of managing health for both the current generation and future generations. This applies to both the father and the mother as both can pass on epigenetic traits.

Modes of epigenetic modification

Some well-characterized modes of epigenetic modification include DNA methylation, chromatin remodeling and histone modification.

DNA methylation is a biological process by which methyl groups are added to the DNA molecule. Methylation can change the activity of a DNA segment without changing the sequence. DNA methylation is essential for normal development and is associated with key processes including genomic imprinting, X-chromosome inactivation, repression of transposable elements, aging, and carcinogenesis.

Chromatin remodeling is the modification of chromatin architecture to allow access of the condensed genomic DNA to the regulatory machinery of your cells, and thereby control gene expression. It plays a regulatory role in key biological processes including DNA replication and repair; cell death; chromosome segregation and development and differentiation of cell types.

Histones are subject to post translational modification. Such modifications include methylation, acetylation and phosphorylation. This affects their function of gene regulation. In general, genes that are active have less bound histone.

Figure 2-10 Epigenetic changes can change the expression of genes. Epigenetic mechanisms are affected by factors including early development, environmental chemicals, drugs and pharmaceuticals, aging, diet and fitness. They can turn genes up or down, on or off.

While these epigenetic DNA modifications do not change the DNA sequence, they can affect gene activity. Your DNA is your blueprint, but it is not your destiny. Environmental influences including your diet and exercise, stress and wellness, development and aging, exposure to pollutants and pharmaceuticals impact the epigenome. 

Patterns of epigenome modification vary between individuals, among different tissues within an individual, and even between different cells from the same tissue. Emerging evidence suggests that gene function, modulated by epigenetic modification of histones (acetylation and methylation) and DNA methylation can affect development. Both genetic and epigenetic factors interact to make you unique!

Figure 2-11 A model for the interactions of genetic and environmental factors in the predisposition to and development of alcoholism. Emerging evidence suggests that gene function can be modulated by alcohol-induced epigenetic modification of histones (acetylation and methylation) and DNA methylation, which can lead to the development of alcoholism. Both genetic and epigenetic factors may interact in the underlying mechanisms of alcoholism. (Starkman et al., 2012)

Father’s lifestyle habits impact epigenetic outcomes in children

Toxins found in cigarette smoke are associated with many types of cancer. They can trigger the expression of cancer-causing genes and/or the suppression of genes that protect against cancer. If a father smokes and it creates an epigenetic alteration, that epigenetic risk can be passed down to his children, even if the child is a healthy non-smoker. (Zong et al., 2019)