How nurture changes nature

I attended the Society for Neuroscience 2008 annual conference for work, as a member of the media. Although I didn't formally write anything up, I did attend two press conferences. One of which Tiptoe wrote about here on addiction and impaired insight (via press release, which was accurate to what was said during the conference), and one that I'm going to summarize here.

In some sense, your genes are your genes. You're born with 'em, you die with 'em. Other than in cases like cancer, they don't change. Clearly, however, our environment effects us. When fair skinned people stand out in the sun, they get tan (or they burn). When we diet, our metabolisms slow. If we keep dieting, they stay slow. And, researchers are finding out, traumatic experiences early in life can permanently change the brain.

The body can turn genes on and off via different environmental cues by adding and subtracting methyl groups (teensy little molecules) that they attach to the DNA. Because DNA is super-long, it has to coil around itself like a huge ball of yarn. But if a gene is going to make a protein, it can't be in the tightly wound part, or else all of the other proteins in the cell can't get to the gene. Adding a methyl group (among other things) alters the ability of the cell to read the gene, literally silencing it and preventing access to the protein-making machinery of the cell.

This whole process is known as epigenetics. Some genes that have been epigenetically changed during fetal development (and therefore before the formation of the sex cells) can be inherited. Most aren't.

And it turns out that trauma in early life can prevent a specific gene (BDNF- brain derived neurotrophic factor) from ever turning on. BDNF is one of the big master switches in the brain. Among other things, BDNF is active in areas of the brain responsible for learning, memory and higher thinking. Abused rats showed decreased levels of BDNF long after abuse and neglect had stopped, and they also showed many anxiety traits. These epigenetic changes were primarily found in the amydala, the center of the brain that controls anxiety and fear.

For a full summary click here and scroll down to page two.

Earlier, unrelated research on the brains of people who had died by suicide found numerous epigenetic changes in the GABA genes when compared to those who had died from other causes. GABA is a neurotransmitter linked to mood regulation.

Writes Peter Kramer in his blog, In Practice:

"...in the face of adversity, certain genes in the brain will be methylated, effectively shutting them down. Once they occur, these changes are difficult to reverse, creating stable disabilities, perhaps for the remainder of a life. Bad experience gives mammals a different genetics and different brains."

Childhood abuse is generally thought of as a HUGE risk factor for pretty much any sort of mental illness. It has also been tentatively linked to bulimia and bulimic behaviors. These studies, among many others, only help to emphasize that a biologically-based illness can be influenced by the environment. And with this research, they're finding out how it might happen at the biochemical level, and how these changes might one day be reversed.

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4 comments:

seeleelive (for the love of peanut butter) said...

Hi.....Just found your blog.... I had time to read a little bit of it but i have an 830 am class tomorrow. I look forward to spending more time and going through the rest of your posts. your header is beautiful, and wow. nourishment is key, i am totally with you on that one. I am 8 months into recovery from anorexia and a freshman in college and blogging has really helped me. I hope you check mine out.
I want to inspire, educate, learn and grow. I want to be a motivational speaker, a writer, and stand up against the poisonous message of the media. Amen!

Anonymous said...

I'm so confused! At first, many years ago, I thought that my anxiousness and later anorexia might have been related to the fact that my mom was absent for several months when I was an infant; she had a very serious case of postpartum depression and was hospitalized. But then, I entered the phase in which things like that seemed to be "blaming the parent," which I don't want to do. But now, the research you describe makes me wonder again if my mom's absence could have been a "trauma" that turned off a gene! AT some level, it doesn't matter what the cause was, but does this mean I'm permanently screwed because the switch never went on?

Carrie Arnold said...

Anon,

Not necessarily. Because if environment can change the brain once, it can do it again. And environment this time can be therapy, recovery, etc.

And nor does your experiences mean that a gene was turned off or on. It's just saying that a traumatic experience CAN do these things. Certainly your mother's absense was difficult for you, but it didn't cause your eating disorder. But all of our life experiences do add up and we do ultimately have to deal with them.

ja said...

Great post. Thanks for the info.

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I'm a science writer, a jewelry design artist, a bookworm, a complete geek, and mom to a wonderful kitty. I am also recovering from a decade-plus battle with anorexia nervosa. I believe that complete recovery is possible, and that the first step along that path is full nutrition.

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nour·ish: (v); to sustain with food or nutriment; supply with what is necessary for life, health, and growth; to cherish, foster, keep alive; to strengthen, build up, or promote



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