Epigenetics is the study of heritable changes in gene expression (which genes are expressed and which are not) that do not involve changes in the DNA sequence, i.e., a change in phenotype without a change in genotype, but rather in the way cells read genes.
Epigenetic change is a regular and natural change, although it can also be influenced by various factors, such as age, environment, and lifestyle. Epigenetic modifications can manifest as commonly as the way cells differentiate terminally to become skin, liver, brain, etc. cells. Or, epigenetic change can have more harmful effects that can result in diseases such as cancer.
There are at least three systems known to regulate epigenetics:
- DNA methylation
- Histones
- And gene silencing associated with non-coding RNAs (ncRNAs)
The history of epigenetics
The first studies in this field date back to the 1940s, when, even before it was called that, Conrad H. Waddington and Ernst Hadorn began extensive research focused on combining genetics with developmental biology. As a result of this study, Waddington was the first person to coin the term epigenetics in 1942, which derives from the Greek word “epigenesis,” which originally described the influence of genetic processes on development.
During the 1990s, there was a renewed interest in this field of science, which led to the consolidation of the molecular basis of Conrad Waddington’s observations that environmental stress caused the genetic assimilation of certain characteristics in Drosophila melanogaster, the fruit fly. Since then, research efforts have focused on unraveling the epigenetic mechanisms related to these types of changes.
Currently, DNA methylation is one of the most widely studied epigenetic modifications. Studies on this topic began in 1969 with research conducted by Griffith and Mahler, who suggested that DNA methylation may be important in long-term memory function.
Other important modifications include chromatin remodeling, histone modifications, and non-coding RNA mechanisms. Renewed interest in epigenetics has led to new findings on the relationship between epigenetic changes and a range of disorders, including various cancers, disorders associated with mental retardation, immune disorders, neuropsychiatric disorders, and pediatric disorders.
Epigenetics and environment
The field of epigenetics is growing rapidly, and with it the understanding that both the environment and individual lifestyle can also interact directly with the genome to influence epigenetic change. These changes can be reflected at various stages throughout a person’s life and even in subsequent generations. For example, epidemiological studies in humans have provided evidence that early prenatal and postnatal environmental factors influence the risk of adults developing various chronic diseases and behavioral disorders.
Several studies have shown that children born during the Dutch famine of 1944 to 1945 have higher rates of coronary heart disease and obesity after maternal exposure to famine during early pregnancy compared to those who were not exposed to famine. Lower DNA methylation of the insulin-like growth factor II (IGF2) gene, a well-characterized epigenetic locus, was found to be associated with this exposure. Similarly, adults who were prenatally exposed to famine conditions have been reported to have a significantly higher incidence of schizophrenia.
Research has also shown that a mother’s exposure to pollution could affect her child’s susceptibility to asthma, and her vitamin D intake could change DNA methylation, which influences placental function. However, it does not stop with the mother, as subsequent studies support the idea that the father also influences his child’s health and epigenetic marks.
Lifestyle and epigenetics
Although our epigenetic marks are more stable during adulthood, they are still believed to be dynamic and modifiable by lifestyle choices and environmental influences. It is becoming increasingly clear that epigenetic effects occur not only in the womb, but throughout the course of human life, and that epigenetic changes could be reversed. There are numerous examples of epigenetics showing how different lifestyle choices and environmental exposures can alter the marks on top of DNA and play a role in determining health outcomes.
The environment is being investigated as a powerful influence on epigenetic tags and disease susceptibility. Pollution has become a major focus in this area of research, as scientists are discovering that air pollution could alter methyl tags on DNA and increase the risk of neurodegenerative disease. Interestingly, B vitamins can protect against the harmful epigenetic effects of pollution and can combat the harmful effects that particular matter has on the body.
Diet has also been shown to significantly modify epigenetic tags. The field of nutriepigenomics explores how food and epigenetics work together to influence health and well-being. For example, one study found that a high-fat, low-carbohydrate diet could open chromatin and improve mental capacity through HDAC inhibitors. Other studies have found that certain compounds within the foods we consume may protect against cancer by adjusting methyl marks on oncogenes or tumor suppressor genes. Ultimately, an epigenetic diet can guide people toward the optimal eating regimen, as scientific studies reveal the underlying mechanisms and impact that different foods have on the epigenome and health.
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