As a publisher of children’s books that help explain a donor or surrogate, we are fascinated by the world of epigenetics and the unfolding awareness of the extent of the impact a non-genetic parent has on their child.
At some point we’ve all wondered why someone we know is like they are – is little Jonny such hard work because he’s been overindulged by his parents or is it just his strong personality inherited from his genetic father? Is Sophie brilliant at piano because of her hours of practice or is it inherited musicality?
The discussion used to be ‘nature vs nurture’. Nowadays we know it’s a combination of both nature and nurture; but we are now learning that we are also deeply affected by what genes the nurture ‘turns on’ or not.
This article on twin studies sums this up perfectly: “Twin studies used to be almost the only way to compare the influence of genes against the environment on personality and behaviour. Recent advances in genetics, however, suggest that opposing ‘nature’ to ‘nurture’ is misleading. Genes combine with the environment to produce complex human traits.”
It goes on to say: “Genes influence such traits and behaviours as height, weight, manic-depressive psychosis, alcoholism, cognitive development, reading skills, parenting style, rate of accident occurrence in childhood, television-viewing habits, peer-group selection, timing of first sexual intercourse, marital disruption, and educational and economic attainment.”
But we know our environment can influence most (or even all?) of these too. The question is, just how much of an influence does our upbringing / environment have?
Parents who conceived their child with the help of a donor egg, sperm or embryo find it rewarding that their parenting, and the environment they are creating, has a truly significant role in more than their child’s behaviours.
So what is Epigenetics?
Your genes play an important role in your health, but it is obvious that so do your behaviours and environment, such as what you eat and how physically active you are. It doesn’t matter how athletic your genetic parents; if you lounge around eating potato crisps all day long you are risking coronary heart disease. But it is interesting that your behaviours and environment can actually cause changes that affect the way your genes work – the study of this is Epigenetics.
Dr Emma Meaburn, Senior Lecturer, Birkbeck, University of London explains: “DNA is the set of instructions we are born with that we inherit from our parents that contain all the information needed to build a human. And the DNA sequence contains a code of four letters A, G, C and T. The human DNA code is about three billion of those letters long and it lives in the nucleus of all our cells. It is the information that’s used in our DNA that helps our body grow, function and develop.”
Emma goes on to explain that scientists have slightly different ideas of how Epigenetics is defined, but that broadly, “. . . it can be thought of as an additional layer of information that sits above the DNA, and it regulates how the information contained in our DNA is accessed and used. It regulates that DNA and tells it what molecules it should make when and at what levels – that process is known as gene expression. Importantly, epigenetic marks don’t change the DNA sequence itself. Rather, they are chemical tags or modifications of DNA, and they also change how the DNA is packaged in the cell. It’s this chemical signposting and packaging that helps regulate how the information in DNA is accessed and used and ultimately helps control cell function.”
Similarly, Courtney Griffin, Ph.D., Oklahoma Medical Research Foundation, in this much viewed TED Talk shows Epigenetics as a third and equally important component sitting alongside Nature and Nurture. It is Epigenetics that explains how one identical twin brought up in the same home environment (i.e. with the same nature (DNA) and virtually the same nurture) gets asthma, or autism or bipolar disorder when the other does not.
Courtney explains that Epigenetic marks are small chemical tabs that sit on our chromatin [Chromatin = our DNA (and the genes encoded therein) which is wrapped around clusters of proteins called histones] and help instruct it whether to compact or decompact. These instructions can then affect how the cell reads the underlying genes encoded in the DNA. Some Epigenetic marks can help condense chromatin, obscuring the underlying genes, preventing the cell from being able to read them, effectively turning those genes off. Other Epigenetic marks can help decompress the chromatin, making the gene accessible to the cell so it can turn that gene on. And it is this that makes cells with the same DNA become either, for example, a heart cell, nerve cell, or skin cell.
A cell’s DNA is made up of genes. Epigenetic marks instruct which genes are turned on and which are turned off. And this in turn determines what kind of cell it will be.
Courtney goes on to say: “So, when does all this Epigenetic information get laid down on our chromatin? The answer is during our embryonic development. As the cells begin to divide and receive signals and information from surrounding cells the Epigenetic marks begin to accumulate and then the genes begin to get turned on or off.”
In the world of assisted reproduction this timing of the Epigenetic effects is of real interest – both to families that used a surrogate (how much influence does the surrogate have) and to mothers that carry a baby conceived by donor egg (how much impact does the ‘actual carrying’ have?).
Courtney explains that Epigenetic marks can be influenced by the environment – not just from the surrounding cells, but the food the carrying person eats, the vitamins she takes or the stresses she encounters can all be transmitted as chemical signals though her bloodstream to her developing foetus where they can get laid down as Epigenetic marks that affect the foetus’ own genes and long-term health.
Intergenerational epigenetic effects
Dr Emma Meaburn goes on to explain how far reaching this effect is: “When the embryo is developing in the uterus the epigenetic information for the developing embryo is essentially reset and relayed down. The child’s epigenome is being reset for the child to go on and develop their own epigenetic patterns. The developing embryo’s germ cell lines are also developing at the same time and are also having their epigenetic marks laid down. So, when the embryo is developing inside the womb, if the embryo is exposed to an environmental effect so is its germ cells and it’s those germ cells that will go on to make the third generation – the grandchildren.”
But it doesn’t stop in the womb
The CDC website states: “Your Epigenetics change as you age, both as part of normal development and aging and in response to your behaviours (such as diet and exercise) and environment.”
Whilst only scientifically proven in rats (due to the challenge of studying gene receptors in live humans!), behaviour and environment continues to affect us after our birth. In Courtney’s TED talk (skip to time stamp 12.35 or see note 1 below) she talks us through a study where a mother rat, through licking and grooming her babies, removes the effect of a silencing Epigenetic mark from a gene, effectively turning the gene back on. This gene helps rats cope with stressful situations. The gene then remains ‘on’ throughout their lives.
Further, unlike genetic changes, Epigenetic marks / changes are reversible. As they don’t change your DNA sequence, but how your body reads a DNA sequence, fresh Epigenetic triggers can affect changes – an early lack of licking and grooming can be rectified! Scientists are making terrific progress in designing drugs that can reverse toxic Epigenetic marks to help combat certain diseases.
Epigenetics continues to have an impact post birth. Behaviours and environment can turn genes on or off. And this can continue throughout our lives.
‘Life course epigenetic research’ is still in its infancy, and the focus of the research is on identifying patterns that link early adverse life experiences, to changes in epigenetic patterns, to later health outcomes.
Courtney highlights that there are things we can do now to positively influence our epigenome – eating healthier foods, avoiding cigarettes, cocaine (surprisingly specifically mentioned!) and stress.
So, this brings us back to how much impact can a non-genetic parent actually have?
In this blog we are particularly interested in what degree a mother can positively influence her newborn.
We now know that it is likely that behaviours like hugging and stroking our child could possibly turn an Epigenetic marker on / off – a marker that could potentially help our child better cope with, for example, stress later in life. The mystery of course is what actions trigger which markers and how can we best help our children?
Lindsay Elise Blount recently interviewed Dr Tim Jenkins, Assistant Professor, Cell Biology and Physiology, BYU College of Life Sciences. In the video she asked him if a non-genetic mother could affect how her child will look. He answered that things like how tall you are and basic facial structures can only be determined by the genetic parents. But, especially in early childhood development, babies stare at you while you talk and smile, and it is very likely they will mimic those things – the way your mouth and face move for example. Thus, it is likely you and your child could have a similar smile for example – through real change in the muscle formation in the cheeks. This of course isn’t a change in the genome, but it does result in a real change in some of the features.
So, whilst a mother or father of a donor conceived child may not be able to affect the colour of their hair or eyes; a grumpy resting face or a head thrown back in laughter might well be attributable to them. But more importantly, through Epigenetic impacts, they can potentially have a much more profound impact on, for example, their child’s ability to cope with stress, likelihood to take up smoking, obesity or even their ability to fight diseases.
Olivia Montuschi, Co-founder of the Donor Conception Network, makes an important point in this article in BioNews that we should be mindful of: “The fallacy most commonly associated with classical genetics has been ‘genetic determinism', where more is ascribed to genes that they can truthfully account for. We may see a new fallacy of ‘epigenetic determinism', where epigenetics is used in the same way – for instance to overstate the influence of the recipient mother and impugn the contribution of the donor. Or conversely, we could see a fallacy of ‘epigenetic relativism' where the complexity of epigenetics is used as a pretext to dismiss all claims of genetic influence, which would allow people to dismiss the genetic contribution of the donor as effectively unknowable and therefore irrelevant.”
All this highlights that the egg, sperm or embryo donor and the person carrying the baby and the mother and/or father all have a truly significant role in a child’s life.
The study of Epigenetics, especially as it pertains to donor conceived children, is clearly in its infancy. We do not know to what extent our parenting affects our children. But what a brilliant thought to hold on to: we have the power to positively impact our genes and the genes of our children and their future children. And it’s not a two-way street – they can impact our genes too. So, eat right, sleep long, and avoid stress where possible. Make the changes in your own life and do your best for your child. Not always easy, but worth aiming at!
Note 1: Rats contain a gene called the glucocorticoid receptor and this gene can be expressed, or read, in a certain region of the rat’s brain. When it is, it helps the rat cope with stressful situations. So, the more receptor that the rat has in this region of the brain, the better it will handle stress. There are studies that have shown that interactions between a rat mother and her pups during the first week of their life can have long term consequences for how much glucocorticoid receptor those pups will grow up to have in their brains and therefore how well they will handle stress. When rat pups are born their glucocorticoid receptor gene is surrounded by a number of silencing Epigenetic marks. This effectively turns the gene off. Yet, if a rat mother extensively licks and grooms her pups, basically takes good care of them during the first week of their life, those Epigenetic silencing marks can be removed from the gene. This allows the glucocorticoid receptor gene to turn back on, and it stays on in those pups’ brains throughout their lives. So they grow up to be well-adjusted animals who deal well with stress. If a rat mother ignores her pups, the glucocorticoid receptor gene will maintain those silencing Epigenetic marks, they won’t go away, and they’ll stay in those pups’ brains throughout their lives. These rats will grow up to be very anxious in stressful situations.
Note 2: The image is taken from Wikipedia https://commons.wikimedia.org/wiki/File:DNA_methylation.jpg#/media/File:DNA_methylation.jpg Christoph Bock, Max Planck Institute for Informatics. This image shows a DNA molecule that is methylated on both strands on the center cytosine. DNA methylation plays an important role for epigenetic gene regulation in development and cancer.