DNA differences start in the womb

Newborn twins may share DNA, but they could have different epigenetic profiles. Image: Tish1/Shutterstock

Australian researchers demonstrate the importance of your environment before birth.

Your genes may determine your characteristics, but your environment can affect these genes before you’re even born. Scientists from Murdoch Childrens Research Institute have shown for the first time that the environment experienced while in the womb can have a greater effect on our health in the future than previously thought.

Dr Jeff Craig and his colleagues mapped the epigenetic markers (which tell our genes to switch on or off) of 22 pairs of identical twins and 12 pairs of fraternal twins. Twins were the ideal candidates for this study, which was published in Genome Research, as they share the same mother and, in the case of identical twins, the same DNA, but they have different umbilical cords and amniotic sacs.

By comparing the differences between these markers in identical and non-identical twins, Craig and his colleagues were able to estimate how genes and environment in the womb both contributed to the babies’ epigenetic profiles. And while there were slightly greater differences between the fraternal twins, the researchers have also shown for the first time that identical twins may have the same DNA sequence, but they can have different epigenetic profiles at birth.

This demonstrates that the unique environment in the womb plays a critical role in the development of this profile, according to Craig. “This must be due to events that happened to one twin and not the other whilst in the womb and shows that the experiences in the womb are important in defining the epigenetic profile we are born with,” he says.

One of the events that may play an important role is the amount of the placenta that the twins have access to. “One twin can get the lion’s share of the placenta and the other twin can lose out,” Craig says. “Smaller twins with smaller placentas are generally not as healthy as twins with larger placentas.”

Each twin also has a separate umbilical cord, which may take a different route to get to the placenta to the developing embryo. And the amniotic sacs, which hold the babies until shortly before birth, may also contain slightly different environments.

These variations could have implications for our health later in life, as some of the genes affected by birth weight have also been linked to our growth, metabolism and diseases such as diabetes and heart disease. “We’re starting to get clues about (how) some of these environments in the womb can affect health,” Craig explains.

Knowing our epigenetic profile when we’re born could help us track diseases or modify the risks early in life. “Knowing the result for each of us at birth could help predict and better manage our future health.”

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