Fear can be inherited, mouse study finds

Mice that were conditioned to fear a specific smell passed
down this fear to their offspring, suggesting that traumatic events can affect
gene expression.

Adult male mice were trained to 'fear' the smell of
acetophenone, a chemical commonly used in perfumes for its sweet, floral fragrance,
by being given electric shocks. They then produced offspring that had the same
'startle' response and were seen to shudder when exposed to the smell.

The second-generation offspring — the 'grandchildren' of the
fear-conditioned mice — were also 'extremely sensitive' to the smell.

'Our results allow us to appreciate how the experiences of a
parent, before even conceiving offspring, markedly influence both structure and
function in the nervous sys­tem of subsequent generations', the researchers
from the Emory University School of Medicine, USA, wrote in journal Nature Neuroscience.

The researchers ruled out the possibility that the offspring
were taught to fear the smell, as pups raised by 'foster parents' that had not been
conditioned still showed a fear response.

The mice also showed differences in the parts of the brain
associated with smell. Their offspring had more neurons that produced an odour
receptor protein, Olfr151, which is specifically linked to the smell of
acetophenone.

Even pups born as a result of IVF responded to the smell,
suggesting that the sperm of the fear-conditioned mice was to blame. When the
researchers looked at the sperm DNA, they saw that the Olfr151 area showed epigenetic
changes, meaning that while the DNA itself had not been altered, the way that
the genes would be expressed had changed.

'These types of results are
encouraging as they suggest that transgenerational inheritance exists and is
mediated by epigenetics, but more careful mechanistic study of animal models is
needed before extrapolating such findings to humans', Professor
Wolf Reik from the Babraham Institute commented.

Professor Marcus Pembrey, chair of the Progress
Educational Trust, commented on the study. He said: 'It provides compelling
evidence of biological transmission of such a "memory", together with
associated brain changes, from shocked adult male mice to their sons and then
grandsons'.

'It is high time public health researchers took human
transgenerational responses seriously. I suspect we will not understand the
rise in neuropsychiatric disorders or obesity, diabetes and metabolic
disruptions generally without taking a multigenerational approach', added
Professor Pembrey.