Scientists Find Olfactory "Memory" Passed Between Generations In Mice 118
New submitter Raging Bool writes "The BBC is reporting that acquired phobias or aversions by mice can be passed on to subsequent generations. From the article: 'Experiments showed that a traumatic event could affect the DNA in sperm and alter the brains and behavior of subsequent generations. A Nature Neuroscience study shows mice trained to avoid a smell passed their aversion on to their 'grandchildren.''"
They did not pass "aversion" to their grandkids (Score:5, Informative)
The grandkids had enhanced receptors for that particular smell. They specifically did not test for, and point out in the paper that they do not claim that the AVERSION was passed on, only that F1 and F2 had structures in the brain that are enlarged compared to control, and that are associated with the sense of smell for the chemical that was used to prime the F0 generation.
Much better science-savvy writeup by my cousin on the Nat Geo blog:
http://phenomena.nationalgeographic.com/2013/12/01/mice-inherit-specific-memories-because-epigenetics/ [nationalgeographic.com]
Re:They did not pass "aversion" to their grandkids (Score:5, Informative)
The premise seems to be:
1. There is a gene associated with a brain pathway responding to the smell.
2. The more this gene is expressed, the more the stronger the pathway.
3. Brain functions that depend on this pathway have a feedback mechanism that result in hypomethylation of the gene in at least sperm cells (egg cells weren't mentioned). This increases expression in the descendants. From what I understand, hypo methylation does not entail any alteration of base pair sequences.
4. As the parent post mentioned, this doesn't mean passing on aversion/affinity, but potentially increased sensitivity which may aid in speed of learning these traits.
That's based on my reading of the abstract. The abstract didn't mention any kind of known or discovered chemical signal for the brain activity to result in the hypomethylation in the sperm. My question would be if anything else in the experimental protocol could have triggered this in a manner not directly caused by the brain activity. My next question would be if this work can be reproduced with a different chemical pathway.
DNA methylation (Score:5, Informative)
Although I don't have any evidence (this is /.), it seems clear that this is probably simply yet another manifestation of DNA methylation.
As I understand it, most of the genome is modulated and/or inactivated by DNA methylation of primarily CpG sites (aparently to prevent junk dna from running amok like in cancer, but also to control differentiation/specialization and). Although the mechanisms and pathways for this are currently not well understood, it seems likely that the proteins that governed the response to this stimulus was effectively coded in the DNA already, but inhibited by DNA methylation. By changing the methylation in the DNA of the gametes this response was able to be passed through to the offspring.
The bigger question is how the methylation is done. If it is done by environmental exposure (e.g, the brain and the gamete cells are over-exposed to the same stimulus from the bloodstream and respond the the same way by changing the methylation pattern to favor a response to that stimulus), that seems fairly straightforward. If, however, the brain can create simulation that causes specific methylation in the gamets, that is a whole nuther ball of wax...
In this experiment they targeted a specific olfactory pathway in the mice (Olfr151) and trained them with a behavior. Apparently, in later generations there was less methylation of the gene corresponding to this pathway providing a more enhanced response to this smell and apparently learned to distinguish this smell better. To me that isn't transferring a memory, it's really more like pre-conditioning to match a learned state.
The difference is subtle, but one way to look at it it like earning money vs inheriting it where the memory is the "how-to-make-money" part and the dna-methylation pattern is the "money". Although the offspring still have money, their behavior is not necessarily the same as the parents.