Environment changes the genome in the womb

Even in the womb, the environment shapes the genome of the child

07/16/2012

Although the DNA determines the foundations of a human's development, the hereditary factors change as a result of the so-called epigenetic effect due to environmental influences. These changes seem to start in the womb, according to a study by Australian researchers from the Murdoch Childrens Research Institute in Melbourne.

Researchers led by Jeffrey Craig and Richard Saffery have studied the genetic makeup of "22 monozygotic twin pairs and 12 non-identical twin pairs" immediately after birth and "mapped their epigenetic markers," according to the Murdoch Childrens Research Institute. Surprisingly, they found that the identical twins already had marked differences in the expression of their DNA at birth - the so-called epigenetic profile. Obviously, the different environmental influences in the womb affect the methylation of DNA, turning certain genes on or off.

Epigenetics - Inheritance Theory of Environmental Influences
After the importance of DNA has been assessed to be almost deterministic for the development of a child in the meantime, it has meanwhile become accepted that the environmental influences via the effect of epigenetics have a greater share of development than previously assumed. The epigenetic effect determines which genes are activated or deactivated. This effect is conditioned biochemically by the so-called methylation of DNA. It forms methyl groups on certain genes, which can be passed on in cell properties to daughter cells that are not explicitly codified by the DNA. Since this has added an extra layer to heredity, scientists speak of epigenetics

In their study, the Australian researchers investigated when epigenetic changes begin in humans by analyzing the DNA methylation of twins immediately after birth. For the first time, their study "on a genome-wide scale shows that identical twins sharing the same DNA sequence can have different epigenetics at birth," the researchers report in the Murdoch Childrens Research Institute.

Environmental conditions change the genetic material
It has long been known that the environment can influence the genetic makeup of a person through the effects of epigenetics. The idea of ​​a fixed, immutable DNA is long outdated. Rather, numerous studies indicate that a person's way of life (eg, through eating, drinking, or exposure to environmental toxins) has a significant impact on DNA methylation. Thus, the hereditary changes in the course of life, but so far remained unclear whether the effect may begin already in the womb. The Australian researchers have now come to the bottom of this question with astonishingly clear results. At the epigenetic level, clear differences were found in the samples taken from the placenta, the umbilical cord and the umbilical cord blood, even in monozygotic twins. These are due to events that happened to a twin in the womb and not to the other, according to Craig and Saffery. "The study shows that the unique environment in the uterus plays a key role in building the epigenetic profile," said Jeffrey Craig in a news release from the Murdoch Childrens Research Institute.

Different environmental influences of twins in the womb
In fact, the environmental influences on the twins in the womb are by no means identical, because the embryos often have their own umbilical cord and, in more than 95 percent of cases, their own amniotic sac, "explained Jeffrey Craig. The environmental conditions are therefore quite different individually. The variable environmental influences mean that the epigenetic profile of identical twins can develop extremely differently in the womb. This finding has "potentially far-reaching effects on human health, as many diseases, such as diabetes, are likely to develop very early in life," the Australian researchers concluded.

Disease prediction using epigenetics
According to Craig and Saffery, epigenetics has a decisive influence on the development of various diseases, and it is important to "identify and track this potential." This would enable disease risk to be recognized early in life. It may also be possible to avoid individual epigenetic health threats through a "specific environment or dietary intervention," Australian researchers hope. Their statements are also corroborated by the observed epigenetic differences in twins with different birth weights. Because the lighter twins had "especially in genes that are predisposed to diseases that were previously associated with low birthweight" changes, the scientists report in the press release of the Murdoch Childrens Research Institute. (Fp)

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