Epigenetics: Holocaust trauma passed down the generations?

Genetic expression adjustments linked to stress and trauma may be inherited by children, a study has claimed. The findings may support the view that the effects of life experiences on gene expression could be passed on to the next generation. 

Researchers at the Mount Sinai Hospital, New York analysed a gene associated with stress hormones, and known to be affected by trauma, in 32 Jewish people who experienced the Holocaust and their children. They compared the results to Jewish families who were living outside Europe during World War Two and found methylation changes in the Holocaust survivors and their children that were not present in the control group.

After ruling out the possibility that the stress indicators in the children's genes could be caused by their own childhood trauma, the researchers concluded that they had inherited their parents' epigenetics changes. 'The gene changes in the children could only be attributed to Holocaust exposure in the parents,' said Professor Rachel Yehuda, who co-authored the study.

Environmental factors, such as diet, smoking and stress, can alter a person's genetic expression though chemical tags attached to DNA that turns genes on and off. While it is widely known that we inherit genes from our parents, these epigenetic changes may also be passed on and lead to changes in the way our DNA is expressed, impacting on the health of future generations, explains The Guardian.

Previous studies have shown how smoking before puberty could lead to men fathering heavier sons, indicating that early-life exposures can induce transgenerational effects in the next generation (see BioNews 749). Another study found that exposure to famine could be linked to schizophrenia in offspring.

'To our knowledge, this provides the first demonstration of transmission of pre-conception stress effects resulting in epigenetic changes in both the exposed parents and their offspring in humans,' said Professor Yehuda. 'It's a lot to wrap our heads around. It's certainly an opportunity to learn a lot of important things about how we adapt to our environment and how we might pass on environmental resilience.' The precise molecular mechanism for this remains unknown, however.

Some commentators have treated the findings with caution. Professor Jerry Coyne, of the Department of Ecology and Evolution at the University of Chicago, said that the study 'suffers from formidable problems that call its conclusions into question'. On his blog, Professor Coyne provides six additional problems with the conclusions drawn by the study.

Professor John Greally at the Albert Einstein College of Medicine, New York, agreed the study has its limitations. 'The story being told by the Holocaust study is indeed fascinating as a scientific possibility, and will no doubt prompt others to pursue similar studies. Unfortunately, the story is typical of many in the field of epigenetics, with conclusions drawn based on uninterpretable studies', he said.

However, Marcus Pembrey, emeritus professor of paediatric genetics at University College London's Institute of Child Health and a patron of the Progress Educational Trust, which publishes BioNews, told the Guardian that the study is a small step towards showing how intergenerational effects are not just transmitted by social influences or regular genetic inheritance (see also BioNews 817).

'[This] paper makes some useful progress. What we're getting here is the very beginnings of an understanding of how one generation responds to the experiences of the previous generation. It's fine-tuning the way your genes respond to the world', he said.