Tag Archives: Gene expression

The Nutcracker – or how experiences get under our skin

Walking along the shopping street near us we saw several man-high Nutcracker figures in the shop windows as Christmas decorations. They looked exactly as the Nutcracker costume used in the ballet we attended two years ago at the Budapest Opera House. Which is why my 11-year-old daughter started humming away on Tjajkovskij’s Nutcracker on our way home. She hummed the part when the rodents come out at night and try to steal the Nutcracker from the little girl. I remember that made a big impression on her.

Yet, my daughter neither knew which tune she was singing or where it came from. It was her brain that picked up one of its imprinted associations and had a little run about it.

That’s just how we learn – by association. It is a use it or lose it game in children and the younger they are, the more circuits the brain is capable of building up. Brain research in the past decade has clearly delivered its message: the more circuits the child builds up, the faster and broader its thinking goes, and the smarter the child becomes.

By age five the least advantaged children have been exposed to 30 million less words compared to children in the highest socioeconomic groups in Northern America. Consequently, the development of their language skills will differ. The PISA test results reflect this trend: in Australia a difference, equivalent to two-and-a-half years of schooling, separates the scores of students in the highest and lowest socio-economic groups.

But not only does the environment affect children’s brains and learning – it also gets under their skin. In fact, it modifies their genes in ways that we are only beginning to understand.


Photo: Fanni Sarkadi

I still remember a book my father gave me called The Double Helix, describing the discovery of the structure of our DNA. It was the story of Watson and Crick who were awarded the Nobel Prize for that discovery. I was fascinated: everything was coded in our genes and if only humanity got around to brake the code we would know all about human disease and what our futures might entail.

Through the human genome project the code was indeed described almost down to the last gene, just so that we would discover that things are not that simple. Genes can be turned on and off in a number of ways, interacting with each other and the environment – a phenomenon called epigenetics.

Through the chemical process of methylation, our DNA becomes modified as a result of environmental exposure. This means that molecules bind to the DNA, affecting its structure and the way it “acts” within the cell environment. The discovery of epigenetic processes marks a new era of genetics, as significant as the description of the double helix.

An example of what happens is demonstrated in a study of adults with posttraumatic stress disorder where those who have been exposed to childhood maltreatment showed specific epigenetic modifications to their DNA, very dissimilar to persons traumatised later in life. A recent study of twins suggests that not even twins share the same epigenetic programming: some pairs were already different in their methylation patterns at birth, some were similar, but became more different, while some followed the expected pattern of further increasing similarities over time.

Although the pathways through which epigenetic programming happens are not fully understood, if genes required for brain development do not activate as they should, the effects will be visible. MRI scans of the brains of children who have been exposed to poverty show less white and grey matter as well as less hippocampal volumes. The hippocampus is involved in associative memory and is very stress sensitive.

Now here comes the Christmas gift: effects of poverty on the hippocampus were mediated by parental care. Supportiveness decreased the effect, whereas hostility increased it. Thus, caring parents will always make a difference for their children in the face of adversity.

In terms of public policy this means that all children should be exposed to a loving and supportive environment, adequate stimulation, and a little Tjajkovskij to fend off delinquency