Genetics and Genomics: Unraveling New Opportunities for Addiction Treatment and Education
Progress in the field of genomics has come a long way since 1865 when Mendel first discovered the laws of genetics. We have moved from understanding the sequence of a single strand of DNA to sequencing the entire human genome in 2003, and now international studies of genetic variations across multiple populations. With this ever growing knowledge about the human genome come limitless opportunities for utilizing this information for the treatment of addictions. In this editorial, we will give an overview of genomics, discuss the latest genomic findings as they relate to addictions treatment, the role of nurse educators in incorporating genomics into course curriculum, and social and ethical challenges involved with genomic medicine and research.
The human genome is estimated to contain 30,000 genes, and the functions are still unknown for over 50% of the genes that have currently been discovered. A gene is a segment of DNA containing all of the information needed to encode for a specific protein. The order of base pairs in a gene determines which protein it encodes for. While the process to translate genes to proteins occurs naturally in the body, sometimes mistakes can happen. Mutations in the genome can occur which can affect how the gene is expressed, by changing the corresponding protein and its function. Mutations called polymorphisms, considered to occur in at least 1% of the population, are largely responsible for determining risk for disease, and differences between how humans respond to treatment. The most common mutations are single nucleotide polymorphisms (SNPs) and copy number polymorphisms(CNVs) where there is loss, gain, or duplication of genes in certain regions (Mroziewicz & Tyndale, 2010).
Estimating the risk for addiction involves determining the inheritability accounted for by both genetics and the environment. A person may have a strong family history of addiction, but the genes for addiction may not be expressed and “penetrated” in certain individuals, while other people with the same family history become addicted almost immediately following their first use of a substance. Thus, no one is “born an addict” There are between 50 and 100 genes influencing addiction and variation in several genes each contribute a small amount of risk.
The study of epigenetics is critical to understanding the nature of addiction. Epigenetics has been aptly called the “ghost in your genes,” according to the NOVA television program on Epigenetics on PBS that aired in July 2007 (http://www.pbs.org/wgbh/nova/body/epigenetics.html), discussing, for example, how identical twins can be different, while the DNA structure does not change. Epigenetics provide the signals that genes receive from inside the cell, other cells and the environment that may contribute to addiction. Common environmental influences include pregnancy (e.g., nutrition of mother, infection, alcohol use, nicotine use, drug use), abuse, trauma, stress, and illness (Doehring, Geisslinger & Lotsch, 2011). If inheritability accounts for about 50% of the etiology of addiction, then epigenetics have equal influence. We understand then, that we inherit the risk for addiction, inheriting small contributions from many genes that interact with environmental stressors. Histone acetylation is an epigenetic mechanism, for example, that alters gene expression when cocaine is used, contributing to addiction (Renthal & Nestler, 2008).