Malleable Genetics

Richard Hill

 

Published in The Neuropsychotherapist Issue #1

 
Just when we thought our knowledge base had expanded exponentially with the introduction of brain plasticity, a new topic enters the conversation—genetics. We used to think the brain was immutable, and until recent years, so went the thinking on DNA. In fact it is turning out that genes are as capable of modification as the brain. Both have some level of fixation along with plasticity that allows wiring pathways and gene expression to change with experience over time. It can be seen quite pointedly in genetically identical twins who have common DNA-driven similarities, yet differences develop over time in response to their personal experience (Kaminsky et al., 2009).

DNA, the molecule that acts as long-term storage for our genetic information, is also capable of regulating its own use. The vast majority of our DNA is not dedicated to protein production. Sometimes called “junk DNA”, we are now slowly discovering the details of non-protein coding DNA that gives rise to various factors and RNA strands acting to regulate, stimulate, and disrupt the activity of protein production. Much of this is an epigenetic response, or a response that is specific to the nature of the individual’s experience within the context of environmental conditions. This represents an enormous breakthrough in the understanding of our malleable biology.

Epigenetics involves heritable changes being made to the process of gene expression without changes being made in the underlying DNA sequence (Levenson & Sweatt, 2005). In other words, only a well defined portion of the genetic possibilities within the DNA are expressed and the rest are permanently, temporarily or semi-permanently turned off. In the language of geneticists, the universal DNA genotype is epigenetically changed to a cell-specific phenotype. The detail of epigenetic action is complex, but the principles are quite straightforward. By adding or subtracting chemicals, it is possible to “silence” a gene or make it impossible for that gene to be expressed in that cell or any of its daughter cells. This is not exactly the same process we talk about when referring to turning genes on and off, which is more about utilising genes that are readily available only in relation to particular needs at the time. Genes that are epigenetically silenced are taken completely out of the picture.

One way that a gene is silenced is when chemical alterations are made to tiny chemical tails that emerge from each of the eight histones. Addition or subtraction of these chemicals allows or disallows the transcription factors to attach to the promoter region, the most discussed process being acetylation. If we just look at the acetylation process, we see that when a histone tail is acetylated, the difference in ionic (electrochemical) charge between the histone and the section of DNA wrapped around it is neutralised. The larger the difference in charge between objects, the stronger the electromagnetic attraction. The effect of acetylation in neutralising this difference is that the DNA is looser and therefore accessible to transcription factors. When the histone tail is deacetylised, the difference in charge increases, which causes the DNA to wrap tightly around the histone, making it impossible for transcription to occur (Grunstein, 1997).

Another entirely different silencing mechanism is a change added onto the DNA code itself. In particular positions, usually near the promoter region in the gene (at what is described as CpG nucleotides), the cytosine “letter” of the DNA code is methylated, which blocks the transcription factor from binding to the promoter region and, again, stops gene expression (Comb & Goodman, 1990). The crucial point here is that through a series of intricate and elegant processes that might evoke impressions of a symphony, the information in our genes is constantly being brought into activity or silenced.

Brain plasticity has revolutionised our thinking about our capacity to make positive changes in our lives. Epigenetics is one of the ways that the body “writes down” and memorises our ongoing life experience. What we do, when we do it, and how we feel about it while we are doing it contribute to the way experience utilises the building materials in our DNA to construct the person that we see in the bathroom mirror and in the mirror of our friends, family, and loved ones.

Brain plasticity has revolutionised our thinking about our capacity to make positive changes in our lives. Epigenetics is one of the ways that the body “writes down” and memorises our ongoing life experience. What we do, when we do it, and how we feel about it while we are doing it contribute to the way experience utilises the building materials in our DNA to construct the person that we see in the bathroom mirror and in the mirror of our friends, family, and loved ones.



Richard Hill, MA, MEd, has had an eclectic and fascinating journey to become an internationally recognised speaker and educator on the mind, the brain, psychosocial genomics and the human condition. Richard is a practicing psychotherapist, author and developer of the Curiosity Oriented Approach. He is also the creator and host of the online interview program, MindScience TV.

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