Researchers find link between genetic variation and alcohol dependence

Virginia Commonwealth University School of Medicine researchers have discovered a biological clue that could help explain why some drinkers develop a dependence on alcohol and others do not.

The findings move researchers closer to identifying those at risk for addiction early and designing better drug treatments to help people stop drinking.

About 18 million people in the United States have an alcohol use disorder, according to National Institutes of Health statistics. The vast majority go untreated.

"There are few and inadequate pharmacological treatments to help people who want to stop drinking, because this is a terrifically difficult human genetics problem," said Jill C. Bettinger, Ph.D., associate professor in the Department of Pharmacology and Toxicology, VCU School of Medicine. "If we can better understand the molecular effects of alcohol, we can design more rational treatments and even warn people who are more susceptible to developing a dependence."

Bettinger is the senior author of a paper, "SWI/SNF Chromatin Remodeling Regulates Alcohol Response Behaviors in Caenorhabditis Elegans and is Associated With Alcohol Dependence in Humans," published Feb. 23 in the journal Proceedings of the National Academy of Sciences.

The paper describes how researchers examined the role of a protein complex - called switching defective/sucrose nonfermenting (SWI/SNF) -- in determining the behavioral response of roundworms to alcohol.

Alcoholism and Genetics

Alcoholism can be passed down from parent to child, but not in the same way as Alzheimer's or cancer. How exactly is it passed on?

In biology class, most of us were taught to believe that specific traits are passed on through our genes: if I have the “Alzheimer’s gene” or the “breast cancer gene,” there’s a probable chance that my son or daughter will carry that gene. However, what about more “complex” diseases like depression, or alcoholism? While alcoholism does tend to run in families - and has a genetic component - how exactly is it passed on?

In recent years, more and more studies are showing that there is another level of inheritance at work: epigenetics. Literally “above the genome,” epigenetic marks are chemical “tags” that can be put on or taken off DNA, and their purpose is to control the expression of genes. Some tags turn genes on, while others turn genes off. These tags come in the form of molecules called methyl groups or acetyl groups, and they can also appear on the outside of the DNA strand. In the nucleus of every cell, the very long strands of DNA coil around proteins called histones; these histones can be more “open” or “closed,” depending on what tags reside on the surface.

These “tags” can be helpful and are very important for many biological processes. For example, in the development of an embryo into a baby, epigenetics plays a huge role in making sure embryonic cells differentiate at the right time and place. Ever wonder how a small handful of cells become heart and lung and brain cells, and all the other cells in our bodies? Since every single cell contains all of our DNA, some genes have to be turned off, while others left on, in order for there to be different types of cells.