Although previous studies have shown that identical twins do
have different sets of epigenetic markers, it was thought that the changes occurred
after birth, when the twins experience different environments. However, in this, the first analysis of the epigenetic profiles of newborn human babies, the team from Murdoch Children's Research
Institute, Australia show that differences are already apparent straight after
'Twins, like the rest of us, sit in their own amniotic sac
and have their own individual experiences', lead researcher Dr Jeffrey Craig told
International Business Times.
The study, published in Genome Research, suggests that
even small differences in womb environment, such as availability of nutrients or
the influence of the placenta and umbilical cord, could be responsible.
Dr Craig added: 'Sometimes one placenta could be in the best
place in the womb, while the other twin might be shunted off to the side
The results also showed that twins who shared a placenta
were even more likely to be epigenetically different, potentially because the
twins would have had to share the same source of nutrition, and so one would potentially get
more than the other.
The study, which analysed the umbilical cords, cord blood
and placentas from 22 identical and 12 non-identical pairs of twins, showed
that the epigenetic profiles of identical twins were more similar than those of
Additionally, differences in birth weight between the twins
corresponded to differences in epigenetic markers on genes known to be
associated with metabolism, growth and heart disease.
Dr Karen Lillycrop, an epigeneticist at the University of
Southampton, told Science News that current evidence suggests that 'in terms of
metabolism these epigenetic changes can have very long-term effects'.
Co-author Dr Richard Saffery hopes the work will add to our
understanding of how epigenetic changes influence future health: 'This has
potential to identify and track disease risk early in life, or even to modify
risk through specific environmental or dietary interventions'.