The Same Psychiatric Gene Affects The Brain Differently At Different Ages

A new study demonstrates how the very same gene may have opposite effects on the brain at different ages and life stages. b lah

The awkward teen years, a time in our lives characterized by poor decision-making and out-sized emotions, may be the simple result of a still developing brain, the latest scientific research tells us.

Among the key factors influencing brain development is our genome, which is responsible for producing the proteins that regulate how individual brain cells function. But does this genetic impact on our brains change throughout our lives? One group of researchers says “yes.” Their new study demonstrates how the very same gene may have opposite effects on the brain at different ages and life stages. “A gene that has positive effects during puberty can be bad for us in adulthood,” explained Dr. Lukas Pezawas, a professor at the Medical University of Vienna and study leader.

Genes Influence How We Move, Think, Feel, and Behave

Our genes decide the color of our eyes and the shape and strength of our hands. What many of us don’t think about is how our genes are also responsible for producing the proteins that coordinate all the complex biological processes of our bodies, including carrying out thousands of chemical reactions within and among cells. For the most part, every cell in our body contains exactly the same set of genes — approximately 20,000 different genes in total.

However, different cells have different purposes, so which of those genes become active (expressed) inside them and which do not is determined by each individual cell. In fact, each cell turns on only a fraction of its genes and silences the rest. Interestingly, at least a third of the genes that make up the human genome are active in the brain, more than any other part of our bodies.

What it means for a gene to be active or expressed is it is able to produce proteins. However, some genes are only expressed during the early months of human development, and then are silenced after that. What, then, do scientists know about this process? By looking at a gene’s DNA sequence, they understand which protein a particular gene will make. But what they do not yet understand is the amount of protein that will be made, when it will be made, or what cell in a group of similar cells will make it. 

To learn more about genetic influences on the brain, scientists continue to explore specific regions, specific genes, and specific outcomes, as is this case in the current study.

Psychiatric Risk Gene

To begin the study, an international collaboration of scientists enlisted the help of 200 participants and then scanned their brains using MRI technology. After collecting the MRI data, the scientists then analyzed how the COMT gene interacts with the brain at different ages. COMT is a gene that produces the proteins involved in dopamine metabolism. Dopamaine, a neurotransmitter, orchestrates the activity of neurons in the forebrain, the region of our brain where planning and action, concentration, attention, and memory occur. Dopamine also helps regulate movement and emotional responses, as well as pleasure and reward. 

Interestingly, the level of dopamine in our brains is not constant throughout our lifetimes. It rises until we reach adolescence and then falls to a much lower level by the time we reach early adulthood. Scientists believe this is why certain mental illnesses usually start around the period of transition into adulthood. If specific brain functions collapse as a result of irregular dopamine levels, researchers theorize, attention deficit hyperactivity disorder (ADHD), depression, or even schizophrenia may be the result.

In the study, then, the scientists wanted to understand how COMT, the gene connected to dopamine, might affect the networks in the forebrain. What did they discover? The MRI scans of teens, when compared to those of adults, showed very different effects resulting from the COMT gene.

"Our age has a crucial influence on the effects of psychiatric risk genes," Pezawas explained. “Our results also show that there are fundamental differences in the dopamine system between adolescents and adults, which we need to take into account in future treatments.”

In other words, the same drug would affect a teen's brain differently than an adult's brain. 

Source: Meyer BM, Huemer J, Rabl U, et al. Oppositional COMT Val158Met Effects on Resting State Functional Connectivity in Adolescents and Adults. Brain Struct Funct. 2014.