Sperm passes dad’s trauma and poor diet to his kids: Study reveals how a father’s experience plays a key role in the way their child’s cells develop
- Researchers showed that gene markers carrying father’s experience are key to their offspring’s development
- If they deleted those markers in worms, the offspring were left infertile
Scientists have shown how a father’s poor diet, lifestyle and trauma is passed onto his children.
Sperm carries ‘epigenetic’ marks that inform how the baby’s germ cells develop, researchers at UC Santa Cruz have shown.
The study, published today in Nature Communications, is one of the first to explain how a parent’s genetic markers have a direct impact on their children.
It offers some explanation for a study that came out earlier this week, showing the sons of Union Army soldiers had a higher risk of early death if their fathers had been prisoners of war subjected to brutal conditions.
The study, published today in Nature Communications, is one of the first to explain how a parent’s genetic markers can impact their children
Research on epigenetics – the biological study of genes that switch on and off – has gained steam in the past few decades, but particularly in the last few years.
For a long time, scientists dismissed the idea that sperm could carry epigenetic information to their offspring, partly because it is so hard to identify. There are no genetic mutations, rather some genes are prevented from expressing themselves fully.
And yet, more and more studies show that a father’s behavior can be passed down to his children – be it stress, fear, or a slow metabolism from their dad’s poor diet.
However, recent studies on mice and humans have shown that 10 percent of epigenetic information is retained in sperm.
Now, testing roundworms, the lab of Dr Susan Strome has shown that this epigenetic information in sperm, known as ‘histone packaging’, directs the formation of the offspring’s cells.
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The lab focused on an epigenetic marker call H3K27me3, which has been shown to repress gene expression in multiple studies.
Once they removed that marker, the vast majority of the offspring were infertile, showing that the marker was clearer essential for the offspring’s development.
‘These findings show that the DNA packaging in sperm is important, because offspring that did not inherit normal sperm epigenetic marks were sterile, and it is sufficient for normal germline development,’ Strome said.
The next step for Dr Strome’s lab is to look at how a father’s life experience can affect the health of his descendants.
‘The goal is to analyze how the chromatin packaging changes in the parent,’ she said.
‘Whatever gets passed on to the offspring has to go through the germ cells. We want to know which cells experience the environmental factors, how they transmit that information to the germ cells, what changes in the germ cells, and how that impacts the offspring.’
A century ago, there was little to suggest that the impact of a person’s life experience lasted long at all. But that started to change within the field of psychology in the early- to mid-20th century.
First, 19th century French neurologist Jean Martin Charcot was the first to show that trauma caused mental illness, with the first ever study revealing hysteria was not a uterus disorder (commonly treated with hysterectomies) but stemmed from psychological suffering.
Soon after, researchers started to join the dots between trauma, mental illness and physical illness. Among other things, the two World Wars drove researchers to investigate the ramifications of pain and suffering.
Even today, most of us are inclined to see trauma as an immediate experience, perhaps leaving a last impact on people who endured particularly harrowing ordeals.
But now, the medical community broadly agrees that traumatic experiences – such as sexual assault, a tough upbringing, divorce, or the death of a loved-one – has a long-lasting impact on the sufferer’s health.
Trauma puts the body into defense mode, sending blood pumping to your major muscles ready to fight, driving up blood sugar levels, flooding the body with the stress hormone cortisol, with a rush endorphins so we can block out the pain.
That experience – whether it’s momentary or repeated – has an impact on cells.
For example, studies have shown trauma can have a lingering impact the brain, limiting the ability to create memories, and keeping the person on high alert.
It can also increase risks of high blood pressure, diabetes, and heart disease. Last month, Pitt School of Medicine showed sexual assault survivors have double the risk of hypertension. Another study, published in 2015 by Georgia Regents University, showed childhood trauma was linked to hypertension later in life.
As top PTSD researcher Bessel van der Kolk put it in his book The Body Keeps The Score: ‘In response to the trauma itself, and in coping with the dread that persisted long afterward, these patients had learned to shut down the brain areas that transmit the visceral feelings and emotions that accompany and define terror.’
Those changes Van der Kolk describes are the ones that appear to have a ‘transgenerational’ effect.
The mid-20th century gave rise to the relatively new field of epigenetics, the biological study of genes that switch on and off. A turning point for this area of research was the Dutch famine at the end of the Second World War, which led to two generations of smaller-than-average babies being born, and was later tipped as the first recognized example of ‘inherited trauma’.
Since, the field has gained weight, particularly in the last two decades.
A groundbreaking study in 2013 showed mice can inherit their grandparents’ and parents’ fears, and that that fear can even be triggered by the same smell – even if they didn’t experience the pain themselves. Crucially, the team at Emory University showed, this was not the result of a genetic mutation, but of a ‘chemical modification’ to DNA that blocked a gene’s expression, without altering it.
A study in 2017 showed the daughters of Finnish women separated from their parents during the Second World War had higher rates of psychiatric hospitalization.
Earlier this year, a Canadian study showed Indigenous women have a 20 percent higher risk of post-partum depression than white women, which was attributed to generations of trauma and suffering.
Some have even suggested that the staggering, historic rates of poor health in the south, while driven by inactivity and poor diet, could also be tied to the history of trauma suffered in that region.
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