Can epigenetic changes be manipulated?

In the opening story, you saw how epigenetic changes in cytosine methylation of a gene encoding a receptor resulted in behavioral changes in people’s response to stress. In Investigating Life: Gene Expression and Behavior, you learned that epigenetic changes underlie the differences between worker and queen bees. Both examples involve changes in DNA that were triggered by the environment and resulted in altered gene expression.

As in bees, nutrients in the diets of mammals (including humans), such as folic acid and SAM-e (S-adenosyl methinione), contain methyl groups that can participate in reactions that modify DNA. Experiments with mice have shown that feeding young animals a diet enriched with these nutrients causes changes in epigenetic patterns and gene expression that remain throughout life. A new field with the name nutriepigenomics (could you have guessed the name?) has developed to investigate the possibility of altering gene expression in mammals by diet.

Future directions

In addition to the altering of DNA methylation by diet, specific drugs have been developed that target the enzymes involved in this phenomenon. In cancer, gene expression can be altered in many ways, such as by mutation (as you saw in Chapter 11). Cancer cells can alter gene expression though epigenetic mechanisms as well. For example, in some colon cancers, the expression of an important tumor suppressor gene involved in DNA repair is silenced by extensive DNA methylation at the promoter, resulting in uncontrolled cell division. The nucleotide analog 5′-azacytidine blocks DNA methyltransferase and can be employed to combat some cancers, by reducing DNA methylation and halting uncontrolled cell division. Other drugs are being used to block histone modifications that in the tumor cell result in gene expression changes.