ANTH 331: Culture and the Individual EPIGENETICS

What Is Epigenetics? All genetic modifications excluding changes in the actual DNA sequence. Modifications include adding molecules, like methyl groups, to the DNA. This changes the appearance and structure of DNA which alters how that gene can interact with the transcribing molecules in the cell’s nucleus. “epi” means on top of, hence epigenetics – “on top of genes”

Epigenetics and the Epigenome Epigenetics is a system of chemical commands for genes (DNA sequences) that turn genes on, off, down or up in their function. There are four known methods for giving chemical commands to genes, including chromatin remodeling, histone modifications, non-coding RNA and methylation. Methylation is the best understood epigenetic modification. A methyl group consists of 1 carbon atom attached to three hydrogen atoms. Methylation is the addition of methyl groups to specific segments of DNA. The response can be inherited, but once the stressor is taken away, the marks will fade and the DNA code will go back to its original programming. The epigenome is the total inventory of chemical changes that can be made to all genes. We are in the infancy of the study of our epigenome.

Ascribed Epigenetic Inheritance Epigenetic modifications are part of the normal function of cellular DNA in all cells in our bodies. All cells have a complete set of DNA, but only use the genes that are relevant to their job in the body. For example: Epigenetic modifications turn on the instructions for particular cell types, e.g.skin cells, and turn off all other instructions in skin cells. Epigenetic modifications mark genes that are inherited from your mother and genes that are inherited from your father.

Acquired Epigenetic Modifications Epigenetic chemical changes also occur through exposure to environmental triggers that add chemical instructions (pollution, diet, disease, abuse). These changes affect an individual’s gene expression over their lifetime. These kinds of epigenetic modification are transmitted from parents to children over generations, but eventually disappear if subsequent generations are not exposed to the environmental trigger. The number of generations that are affected before the epigenetic changes disappear varies in ways we do not yet understand.

Known Human Parents’ Epigenetic Effects A mother’s exposure to pollution impacts offspring’s asthma susceptibility. Mothers with excessive levels of vitamin D can experience placental malfunction. Pregnant women with high maternal anxiety are known to have children more likely to have asthma. Parental abuse markers are passed to children who then cannot manage stress adequately.

Known Parental Epigenetic Effects (con’t) People who aren’t well-fed as a child are known to have children and grandchildren with higher risks for diabetes and cardiovascular disease. The rise in peanut allergies may be because of baby lotions containing peanut oil. Little kids who are kept very clean are at higher risk for eczema. Men who smoke before puberty tend to have sons who can’t produce sperm, have higher body mass indexes and shorter life expectancies. Fathers are known to epigenetically pass high blood sugar to offspring Fathers are known to epigenetically pass an increased risk of breast cancer to their daughters.

Fathers and Epigenetic Affects on Offspring Exposure to phthalates that are endocrine disruptors found in plastics, personal care products like shaving cream, and in the environment that surrounds us can lead to programing for obesity disruption of hormones linked to changes in male reproduction including androgen levels and quality of semen Exposure to bisphenol-A disrupt fetal development lead to permanent and disruptive changes to the methylation of fetal DNA Low folate levels birth defects and low fertility Fast food diets diabetes Diet with large amounts of methionine, folic acid, betaine, choline, vitamin B12, and zinc. offspring did not perform well in memory tests

Animal Examples of Evidence for Epigenetics When fruit flies are exposed to geldanamycin, they get rough growths on their eyes. This trait is passed on for approximately 13 generations even when generations 2-13 were not exposed to the drug. A pregnant rat was exposed to a chemical that can alter reproductive hormones. It had generations of sick offspring. Smoking and over-eating in rats can make the genes for obesity over- express themselves and the genes for longevity under-express themselves.

Sweden Study In Norrbotten, Sweden in the 19th century there were very few people. If they had a bad harvest, people went hungry. In 1800, 1812, 1821, 1836, & 1856 crops failed and faced starvation. In 1801, 1822, 1828, 1844 & 1863 the crops were bountiful and people ate well. Pregnant women who ate poorly tended to have children with a higher risk for cardiovascular disease. Children who experienced fluctuating food security/ insecurity were known to have children and grandchildren with far shorter lives. When certain socioeconomic variations were controlled the lives osf subsequent generations were shortened by an average of 32 years.

The Future The new evidence for epigenetic inheritance extends the span of evolutionary thinking and is adding to our information on heredity, showing that acquired traits can be heritable. Scientists are learning to manipulate epigenetic markers and are making drugs that will turn off bad genes and turn on good ones. Scientists are hoping to develop epigenetic drugs to treat diabetes, cancer, Alzheimer’s, schizophrenia, autism, and other illnesses/conditions. Epigenetics may shed light on why one identical twin can suffer from asthma or bipolar disorder and the other one doesn’t, or why autism is four times more likely in a boy than a girl.