We are starting to understand the fundamental biological changes which underlie fetal programming. Of particular importance is the field of epigenetics, which means ‘on top’ of genetics.

Epigenetic changes are modifications of DNA, which occur without any alteration in the underlying DNA sequence and can control whether a gene is turned on or off and how much of a particular message is made. Every cell in our body has the same DNA sequence but different genes are turned on or off to make our different tissues, such as muscle or liver.

Epigenetic changes can also be caused by the environment and lead to differences in individual characteristics. In the womb both the mother’s diet and her stress can cause epigenetic changes in the fetus.

The effects of maternal licking and grooming on the epigenetic regulation of GR expression in pups. (Image taken from Feder and Colleagues 2009)

The early emotional environment can lead to long lasting epigenetic changes in the brain. One of the first examples of this came from animal studies of maternal care. Rats pups who were licked and groomed a lot by their mother, showed reduced anxiety and lower stress responses in adulthood. These effects were due to epigenetic changes within the brain of the offspring, specifically at the receptor for the stress hormone cortisol (Weaver and Colleagues, 2004 ). Similar epigenetic modifications of the cortisol receptor were identified in the brain of rat fetuses whose mother’s were exposed to prenatal stress during pregnancy see Mueller and Bale, 2008

In human studies, child abuse has been shown to alter the epigenetic profile of the brain when examined post-mortem (McGowan and Colleagues, 2009), and maternal prenatal stress, caused by violence from the partner, promotes epigenetic changes in the DNA for this same cortisol receptor, in the blood of their adolescent children (Radtke and colleagues, 2011).

These epigenetic changes can be passed down from the mother or the father (see Franklin, 2010 and Champagne, 2008) and may even persist across multiple generations, being passed on from grandparents to grandchildren. Thus, acquired characteristics can sometimes be inherited. However, whilst certain epigenetic changes can last a lifetime, others are much more temporary, and a lot of research is currently being conducted to establish how epigenetic changes can be reversed.

The Molecular Basis of Epigenetics

The two main epigenetic mechanisms are shown below. These are termed DNA methylation and histone modification, and both determine whether the underlying DNA code can be read or not, and thus whether the DNA is able to make RNA. In particular, the methylation of target genes is usually associated with a dramatic reduction in their level of expression.

Two epigenetic mechanisms are described above, histone modifications and DNA methylation both of which determine whether the underlying DNA code can be read or not

The Agouti Mice

One example of the effect of epigenetic changes is shown in a special type of mouse called the Agouti mouse. These animals have the same genes, but have different epigenetic modifications to a single gene, which controls coat colour. During pregnancy, the mother of the smaller mouse with the brown coat was fed a diet rich in supplements, including folic acid. Folic acid serves as a methyl donor, and this allows the agouti gene to become methylated and switched off, resulting in brown fur.

However, the mother of the mouse with the yellow coat was not fed these supplements. As a result, the agouti gene remained unmethylated and expressed in all cells, leading to a yellow colouration of the fur, as well as adult-onset obesity, diabetes, and tumorigenesis. So these genetically identical mice look so radically different due to epigenetic changes, caused in the womb, by their pregnant mothers’ diet.

The Agouti mice above show the effects of different diets during pregnancy
The Agouti mice above show the effects of different diets during pregnancy

Why not take a look at our film for more information on epigenetics and how it relates to fetal programming

Click here to see the video

Posted in: The Science | 3 Comments »

3 Responses to Epigenetics

Extract from “Light on Parenting Conference” 5 May 2012, London – Notes. « Niteo Parent says:
May 10, 2012 at 17:29
Beginbeforebirth is a great resource to learn more about epigenetics, what it is, how it works and the ways in which stress during pregnancy may affect future child development.

Science & Sensibility » Begin Before Birth; Reproductive Researchers Reach Wide Audiences with New Interactive Website says:
September 28, 2012 at 20:36
[…] of the site breaks down the scientific and theoretical literature within study of evolution, epigenetics, placenta and fetal brain, and evidence from animal-based research. Citations are given throughout, […]

What happened to “Charlie” started in his mother’s womb « ACEs Too High says:
January 9, 2013 at 00:17
[…] site has a good section on epigenetics. You think the DNA you’re born with is your blueprint for life? Not quite. Your genes can be […]