Baby Mice Can Inherit Fear of Certain Smells From Their Parents

Epigenetics has become something of a buzzword these days. Researchers have long studied how changes in an organism's DNA sequence affect how genes behave, but epigenetics looks at how environmental factors, like diet or lifestyle, can change gene activity in a way that passes from generation to generation. There's interest in how epigenetics might be connected to conditions ranging from cancer to kidney disease to autism. Yet scientists struggle to pin down the specifics of this phenomenon. As the New Scientist explains:

Previous studies have hinted that stressful events can affect the emotional behaviour or metabolism of future generations, possibly through chemical changes to the DNA that can turn genes off and on – a mechanism known as epigenetic inheritance.

However, although epigenetic changes have been observed, identifying which ones are relevant is a bit like searching for a needle in a haystack. That's because many genes control behaviours or metabolic diseases like obesity.

Now, a new study published in Nature Neuroscience provides "some of the best evidence yet" that behaviors can indeed be passed from one generation to another, the New Scientist says.

In an experiment reminiscent of A Clockwork Orange, researchers trained male mice to fear a cherry blossom-like scent called acetophenone by inducing slight electric shocks every time the smell wafted into the animals' cages. After ten days of this treatment, whenever cherry blossoms were in the air, they report, the mice trained to fear it went on edge. The researchers found that those mice developed more smell receptors associated with that particular scent, which allowed them to detect it at lower concentrations. Additionally, when researchers examined those males' sperm they found that the gene responsible for acetophenone detection was packaged differently compared to the same gene in control mice.

After imprinting those males with a fear of acetophenone, the researchers inseminated females with the scared mice's sperm. The baby mice never met their father, but those sired by a blossom-hating dad had more acetophenone smell receptors. Compared to pups born of other dads, most were also agitated when acetophenone filled the air. This same finding held true for those original males' grandpups.

Information transfer from one generation to another, outside experts told the New Scientist, may play a role in human diseases such as obesity, diabetes and psychiatric disorders. But researchers are far from pinning down the mechanism by which this may be possible, how long these sensitivities may last or whether these seemingly inherited behaviors affect anything more than smell in mice.

In other words, epigenetics is a field still largely obscured by unanswered questions. As Virginia Hughes summarizes at National Geographic, about all we can know for certain is this: "Our bodies are constantly adapting to a changing world. We have many ways of helping our children make that unpredictable world slightly more predictable, and some of those ways seem to be hidden in our genome."

More from Smithsonian.com:

The Toxins that Affected Your Great Grandparents Could Be in Your Genes
These Decapitated Worms Regrow Old Memories Along with New Heads  

Rachel Nuwer | | READ MORE

Rachel Nuwer is a freelance science writer based in Brooklyn.