You may have heard of the human genome. That’s the complete collection of DNA that makes each of us unique. DNA is the molecule in our cells that structures our genes. Genes are capsuled in chromosomes that are located in the center of the cell (called a nucleus) and carry the instructions for how our body works and develops. Genes also aid in how our cells become organs, bones and muscle.
Scientists have been studying the human genome and our DNA for years. Part of the research includes exploring the epigenome — the many chemical compounds and proteins that tell the genome what to do.
Epigenome chemicals and compounds make changes to our genome by attaching to DNA and turning genes on or off, controlling the activity of proteins in specific cells.
When these epigenomic compounds attach to DNA and turn genes on or off, we say they’ve marked the genome. The marks don’t change the DNA sequence, but they do change the way cells use the DNA’s instructions.
Cells are different from one another because different sets of genes are turned on or off in those cells. For example, specialized cells in the eye turn on genes that make proteins that can detect light. Specialized cells in red blood cells turn on proteins that carry oxygen to the rest of the body.
Our cells mostly have the same genome, but the epigenome instructs the cells which genes to turn on and off, also called “gene expression,” and this makes the difference in what the cell goes on to do or become.
Even though the cells in the body hold essentially the same genome, our epigenome can change due to our lifestyle choices and environmental exposures that can include smoking, diet, stress and infectious disease. Some diseases are caused by malfunctions in the proteins due to influences on the epigenomic marks.
Until recently, scientists thought that human diseases were typically caused by changes in the DNA sequence, bacteria and virus infections, or environmental agents. We can now add epigenomic errors to the list of issues that can lead to some forms of cancer and other diseases.
For example, changes in the epigenome can switch on or off genes that are involved in cell growth or the body’s immune response. These changes can result in uncontrolled cell growth, a characteristic of cancer, or lead to a failure of body’s immune system to destroy tumor cells.
Research has also found a connection between inherited genetic errors and a higher risk for certain health conditions, including some that can impact an unborn child. Research is ongoing to discover how much of the epigenome is inherited. Historically, it was believed that the epigenome was restarted every generation, allowing the epigenome to be influenced by new (or old) environmental factors leading to potentially different outcomes than the generation before.
Due to the complexities of these (and other) genetic processes, the fields of genetic testing and genetic counseling have become more utilized. These fields help people understand potential genetic changes and address their risks and/or other health implications. Results of genetic testing can inform individuals and their health care professionals of potential disease risks so increased screening, prevention or other special medical interventions can be employed before the onset of the disease (or help lower the effects of an on-going disease). Genetic counselors can help explain the intricacies of genetics and genetic testing for high-risk pregnancies, children and adults.
A better scientific understanding of how changes in the genome and epigenome contribute to the development of cancer and other diseases may give researchers new ways to prevent, diagnose and treat these diseases.
To support these efforts, the National Institutes of Health’s Cancer Genome Atlas Network is compiling a list of possible epigenomic changes that might lead to disease development. Researchers are comparing the genomes and epigenomes of normal cells with those of cancer cells to see at a cellular level how they differ.
According to the National Institutes of Health and National Institute of Child Health and Human Development, a number of diseases and disorders are linked to epigenetic changes. So far, science has linked these diseases to epigenetics:
The study of our genomes and epigenomes will expand our understanding of the human body and how activity in our cells can lead to different outcomes — sometimes the right outcomes — and sometimes the wrong ones.