‘Memories’ of stress can be passed down from one generation to the next by being transmitted from cell to cell, and so from mother to daughter, research finds.
It follows on from a mouse study which showed that fearful memories of a smell could be passed on from parent to child without the child ever having experienced the smell.
The process, known as ‘epigenetics’, does not mean that the genes themselves are changed by, say, stressful events; rather that there are changes in the way those genes are packaged and expressed.
The study, published in the prestigious journal, Science, provides evidence for a controversial theory, namely that ‘memories’ can be passed down through genetic code (Gaydos et al., 2014).
Many scientists are sceptical about the study of epigenetics, since the mechanism is unproven.
Nevertheless, there is some evidence that ‘memories’ of early life stress can be passed on epigenetically from parents to children, causing a higher rate of adult depression in their offspring (Caspi et al., 2003).
The study takes advantage of a chemical change called ‘methylation’ that takes place in a particular protein called histone H3, which has been well-studied in epigenetics.
The same protein is found in all multicellular animals, from humans down to the worms that were used in this study.
Professor Susan Strome, a biologist at the University of California at Santa Cruz who led the study, said:
“There has been ongoing debate about whether the methylation mark can be passed on through cell divisions and across generations, and we’ve now shown that it is.”
In their research, Professor Strome and colleagues bred worms that had the gene knocked out, which creates the methylation mark.
These were then bred with normal worms.
By following the chromosomes of normal and mutated worms as they divided and grew, the researchers were able to show the critical methylation mark moving from one generation to the next.
Professor Strome concluded:
“Transgenerational epigenetic inheritance is not a solved field–it’s very much in flux.
There are dozens of potential epigenetic markers.
In studies that document parent-to-child epigenetic inheritance, it’s not clear what’s being passed on, and understanding it molecularly is very complicated.
We have a specific example of epigenetic memory that is passed on, and we can see it in the microscope.
It’s one piece of the puzzle.”