Brain Cells Actually Favor One Parent’s Genes Over the Other

Unbeknownst to your rational mind, you may be favoring one parent over another.

At least that’s what a new animal study on gene expression suggests. In short, the study reveals that your brain cells may be unsuspectingly preferential to one parent by expressing that parent’s gene more often than the other’s.

Each brain cell has a copy of two genes — one from your mother and one from your father. But the chances that your brain expresses both genes at the same time are somewhat haphazard, according to the study appearing in the journal Cell.

In the brains of newborn mice, researchers found that 85 percent of cells in a specific brain region tied to mood and emotion activated one parent’s gene or the other gene, while just 15 percent activated both genes simultaneously.

Ten days later, when the mice were considered to have juvenile brains, the opposite occurred — about 90 percent of the brain cells activated both genes at the same time.

What’s more, the researchers found that such discordant gene expression can occur in other parts of the body, including the liver and within muscles.

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The new study adds a wrinkle to the current understanding of genetics and may hold the answer to the cause and incidence of some brain disorders, report the study authors from the University of Utah.

“We usually think of traits in terms of a whole person, or animal. We’re finding that when we look at the level of cells, genetics is much more complicated than we thought,” said senior author Dr. Christopher Gregg, assistant professor of Neurobiology and Anatomy at the University of Utah.

When a Bad Gene Gets Expressed

The study suggests that when brain cells select one gene over the other, the risk of disease rises if the single copy being expressed has a genetic mutation. This may have implications for cognitive and neurological disorders, such as autism, schizophrenia and attention deficit disorder (ADD), note the researchers.

In their studies on mice, the researchers discovered that a preference for expressing a defective gene rather than a healthy one is exactly what happened — some brain cells in the mice expressed a gene with a mutation even when a defective-free gene was also present.

“It has generally been assumed that there is correlation between both copies of a gene,” said co-author Elliott Ferris.

The new study shows that such a correlation does not always occur. “Our new findings reveal a new landscape of diverse effects that shape the expression of maternal and paternal gene copies in the brain according to age, brain region and tissue type,” explained Gregg. “The implication is a new view of genetics, one that starts up close.”

The researchers are building off of previous research related to genetic preference and disease incidence. For example, scientists have found that a gene called DEAF1, which is tied to autism and cognitive disabilities, expresses a single gene copy more frequently in certain parts of the brain.

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Typically, having two gene copies serves as a form of insurance in the event that one gene is defective. However, when the brain cells opt to express the defective gene instead of the healthy one, it could disrupt normal cell behavior and lead to disease.

The variability of gene expression “can profoundly influence the genetic architecture of human disease and brain disorders,” report the authors in Cell.