Epigenetics: Are Genes The New Brains?

Neuroskeptic iconNeuroskepticBy NeuroskepticSep 26, 2013 4:13 PM


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Over at the Pacific Standard, David Dobbs writes on: The Social Life of Genes

It's an excellent piece about epigenetics and gene expression - the process by which particular parts of our DNA are 'switched on', or off, within cells:

Genes can vary their level of activity, as if controlled by dimmer switches. Most cells in your body contain every one of your 22,000 or so genes. But in any given cell at any given time, only a tiny percentage of those genes is active.

This is well-established biology; what's new is the idea that:

The environment could spin the dials on “big sectors of genes, right across the genome” - and that an individual’s social environment might exert a particularly powerful effect. Who you hung out with and how they behaved, in short, could dramatically affect which of your genes spoke up and which stayed quiet - and thus change who you were.

For instance, comparing socially isolated people to others, researchers Cacioppo and Cole found that:

Of roughly 22000 genes in the human genome, the lonely and not-lonely groups showed sharply different gene-expression responses (in leukocytes) in 209 genes. That meant that about one percent of the genome - a considerable portion - was responding differently depending on whether a person felt alone or connected... Whole sectors of genes looked markedly different in the lonely and the socially secure. And many of these genes played roles in inflammatory immune responses...

Good stuff, and there's plenty more detail (including some remarkable studies of bees) in Dobbs' piece. But while reading the article I felt an odd sense of deja vu. Why? I don't know much about genes. I'm a brains guy. But then I realized, that was it - I'd heard this kind of thing before about brains. Here's a bit from near the end of the article, where Dobbs is in conversation with epigeneticist Steven W. Cole. I've just made a little adjustment:

We were in fact skirting the rabbit hole that is the free-will debate. Yet he wanted to make it clear he does not see us as slaves to either environment or brains. "You can’t change your brain. But if we’re even half right about all this, you can change the way your brain behaves - which is almost the same thing. By adjusting your environment you can adjust your brain activity. That’s what we’re doing as we move through life. We’re constantly trying to hunt down that sweet spot between too much challenge and too little. "That’s a really important part of this: To an extent that immunologists and psychologists rarely appreciate, we are architects of our own experience..."

Cole was talking about genes, but couldn't he almost have been discussing brains? I'm thinking here of the recent discussionsaboutneuroplasticity, the idea that the environment can alter brain structure and function. The story is the same: "We used to think that biology determined our lives, but now we know that life can influence biology." There's a lot of truth in that, in both cases. However, if genes are the new brains, then epigeneticists will need to be careful not to fall into the same traps that neuroscientists are only just learning to avoid. One thing we've learned that it's easier to measure brain activity than to interpret it. Brain activity-behaviour correlations are ten a penny, but the mere fact that the brain is activated by something, or activated differently in two groups of people, tells us nothing. Working out what causes what, what's important and what's trivial, is the goal, and it's not an easy one to achieve. There are 22,000 genes; there are some 20,000 voxels in the average fMRI scan of the brain, so even the statistics of analyzing their activations are quite similar. Finally, it seems I'm not the first to spot the parallels here, because three years ago Greg Miller wrote a piece called The Seductive Allure of Behavioral Epigenetics. This was surely an allusion to The Seductive Allure of Neuroscience Explanations, the famous 2008 paper about fMRI.

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