March 8 (UPI) -- How a child behaves and the decisions they make as they grow up may be influenced by a complex interaction between genes inherited from both parents, a study published Tuesday by Cell Reports found.
Although most genes are inherited in pairs, with one copy from each parent, parents exert their genetic influence in different ways, each with a unique impact on hormones and other chemical messengers that control mood and behavior in their offspring.
Based on experiments in mice, certain groups of brain cells rely exclusively on the mother's copy of a gene that is needed to produce essential chemical messengers called neurotransmitters, according to the researchers.
In these cells, the father's copy of the gene remains switched off, they said.
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Conversely, in a different organ, the adrenal gland, certain cells favor the father's copy of the same gene, which produces the stress hormone, adrenaline.
This unexpected switch in parental control of a single gene has consequences for behavior, affecting sons and daughters differently. Certain decisions in sons were controlled by their mother's gene, whereas fathers had control over some decision-making in daughters, according to the researchers.
"We're really intrigued that there is this untapped area of biology that controls our decisions," study co-author Christopher Gregg said in a press release.
Gaining a clearer picture of the genetic factors that shape behavior could help improve the diagnosis and treatment for psychiatric disorders, said Gregg, an associate professor of neurobiology at the University of Utah in Salt Lake City.
Previous studies have shown that reducing stress in childhood can lower future risk for mental health disorders.
For this study, Gregg and his colleagues focused on a gene called dopa decarboxylase, which neurons need to manufacture dopamine, serotonin and noradrenaline.
These are all neurotransmitters, or communication cells within the brain, involved in regulating mood and movement, among other functions.
Both parents' copies of the dopa decarboxylase gene are active in the brain, but neurotransmitters appear to prefer the mother's, according to the researchers.
To investigate whether that preference occurred in particular cells or brain regions, the researchers genetically engineered mice to attach a fluorescent tag to the dopa decarboxylase enzyme that showed red if it was produced using a gene inherited from mom or blue if a gene from dad had been used.
With this tag, they could simply look under a microscope to see which parent's copy of the gene was active.
After examining the entire mouse brain, they found 11 brain regions that contained groups of neurons that use only the mom's copy of the dopa decarboxylase gene.
Dopa decarboxylase is also used in the adrenal gland, where it helps produce the adrenaline hormone that triggers "flight or fight" responses to danger or stress.
In the adrenal gland, researchers found groups of cells that relied exclusively on the dopa decarboxylase gene copy inherited from dad.
The findings are a first step toward understanding how a parent's genes may affect more routine behaviors and related health conditions in people, from mental illnesses and addiction to cancer and Alzheimer's disease, the researchers said.
"The brain-adrenal axis is a very important part of mammalian biology that controls behavior and affects stress, mood, metabolism and decision-making," Gregg said.
"I dream of this new field of decision genetics, where we systematically uncover the parental gene copies that control specific decisions and actions in particular contexts," he said.
