Epigenetics and Olfactory Experience

Traumatic experiences dramatically effect neurological functioning and memories of the person that experienced the specific trauma. Although, how does this effect future generations? Surely a mother that experiences a trauma will nurture her children differently since she will likely have different behavior than a mother not exposed to a trauma. As mentioned earlier in this blog, a mother rat's parenting style greatly impacts the epigenome of her children such that neglected pups will have distinctly different epigenetic markers than rats with caring mothers. In turn the neglect causes anxious behaviors and that behavior is often passed down. In this way it is the nurture that effects the rats epigenome. However, it is also possible that the traumatic experience can cause a naturally hereditable fear in the epigenome.

Molecular formula for acetophenone

Researchers Brian Dias and Kerry Ressler investigated the idea of a fear in mice that could be hereditable, and published their results in Nature Neuroscience. Dias and Ressler subjected male mice to "odor fear conditioning" of the smell acetophenone. They paired the fruity smell along with a slight shock on the foot. The next two generations of mice, smelling the odor for the first time in their lives, "had an increased behavioral sensitivity to the F0-conditioned odor, but not to other odors" (Dias & Ressler, 2013). Upon looking at the brains of the subsequent generations the researchers found increased amounts of neurological receptors in the olfactory system that detect the smell of acetophenone.

In order to prove that this was epigenetically inherited rather than by how the pups were nurtured, the scientists harvested the sperm of the first generation and conducted in vitro fertilization, only to find the following generations still had the same odor fear as the father or grandfather. Therefore the sperm was determined to be the cause. Investigation showed an altered epigenetic methylation signature at the Olfr151 (M71) locus in the sperm to be the particular location for the heritable olfactory fear.

It seems strange that it might be evolutionarily deleterious to inherit the fears of a parent. In an interview with a National Geographic journalist Dias explains his supposition, "And why, evolutionarily, would a parent pass down such specific information? “So that when the offspring, or descending generations, encounter that environment later in life, they’ll know how to behave appropriately,” Dias said" (Hughes, 2013).  


Indeed, it seems that epigenetics is working as a plastic mechanism for evolutionary change. Olfaction is a key sense that humans as well as a myriad of animals rely on for awareness of their surroundings. This research identifies that epigenetics is the cause for a heritable fear and poses questions as to what other types of fears or information can be passed to future generations via the senses. Epigenetics is aiding in animals survival behaviors by allowing animals to give their children heightened awareness toward particular objects or surroundings. A recognition of a negative smell by mechanisms other than nurture enhances animals abilities to quickly adapt to situations in an instinctual manner. 



References:

Dias, B. G., & Ressler, K. J. (2013). Parental olfactory experience influences behavior and neural structure in subsequent generations. Nat Neurosci, 17(1), 89-96. doi: 10.1038/nn.3594

http://www.nature.com/neuro/journal/v17/n1/abs/nn.3594.html#supplementary-information

Hughes, V. (2013). Mice Inherit the Fears of Their Fathers. National Geographic Magazine(Only Human). 

Picture References: All pictures accessed on 21/05/15 and are referenced appearing from top to bottom of blog

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