Study of Holocaust survivors finds trauma passed on to children's genes

Genetic changes stemming from the trauma suffered by Holocaust
survivors are capable of being passed on to their children, the clearest
sign yet that one person’s life experience can affect subsequent
generations.
The conclusion www.biologicalpsychiatryjournal.com/article/S0006-3223%2815%
led by Rachel Yehuda stems from the genetic study of 32 Jewish men and
women who had either been interned in a Nazi concentration camp,
witnessed or experienced torture or who had had to hide during the
second world war.
They also analysed the genes of their children, who are known to have
increased likelihood of stress disorders, and compared the results with
Jewish families who were living outside of Europe during the war. “The
gene changes in the children could only be attributed to Holocaust
exposure in the parents,” said Yehuda.


Her team’s work is the clearest example in humans of the transmission
of trauma to a child via what is called “epigenetic inheritance” - the
idea that environmental influences such as smoking, diet and stress can
affect the genes of your children and possibly even grandchildren.
The idea is controversial, as scientific convention states that genes
contained in DNA are the only way to transmit biological information
between generations. However, our genes are modified by the environment
all the time, through chemical tags that attach themselves to our DNA,
switching genes on and off. Recent studies suggest that some of these
tags might somehow be passed through generations, meaning our
environment could have and impact on our children’s health.
Other studies have proposed a more tentative connection between one generation’s experience and the next. For example, www.hongerwinter.nl/item.php?id=32&;amp;language=EN
who were pregnant during a severe famine at the end of the second world
war had an above-average risk of developing schizophrenia. Likewise, www.nature.com/ejhg/journal/v22/n12/full/ejhg201431a.html has showed that men who smoked before puberty fathered heavier sons than those who smoked after.



The team were specifically interested in one region of a gene
associated with the regulation of stress hormones, which is known to be
affected by trauma. “It makes sense to look at this gene,” said Yehuda.
“If there’s a transmitted effect of trauma, it would be in a
stress-related gene that shapes the way we cope with our environment.”

They found epigenetic tags on the very same part of this gene in both
the Holocaust survivors and their offspring, the same correlation was
not found in any of the control group and their children.Through further genetic analysis, the team ruled out the possibility
that the epigenetic changes were a result of trauma that the children
had experienced themselves.
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Advertisement“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 Yehuda, whose
work was published in www.biologicalpsychiatryjournal.com/article/S0006-3223%2815%.
It’s still not clear how these tags might be passed from parent to
child. Genetic information in sperm and eggs is not supposed to be
affected by the environment - any epigenetic tags on DNA had been
thought to be wiped clean soon after fertilisation occurs.
However, www.ncbi.nlm.nih.gov/pubmed/26046444
that some epigenetic tags escape the cleaning process at fertilisation,
slipping through the net. It’s not clear whether the gene changes found
in the study would permanently affect the children’s health, nor do the
results upend any of our theories of evolution.
Whether the gene in question is switched on or off could have a
tremendous impact on how much stress hormone is made and how we cope
with stress, said 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 impact of Holocaust survival on the next generation has been
investigated for years - the challenge has been to show
intergenerational effects are not just transmitted by social influences
from the parents or regular genetic inheritance, said Marcus Pembrey,
emeritus professor of paediatric genetics at University College London.
“Yehuda’s paper makes some useful progress. What we’re getting here
is the very beginnings of a 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.”





www.theguardian.com/science/2015/aug/21/study-of-holocaust-s