Your genes determine much about you, but environment can have a strong
influence on your genes even before birth, with consequences that can last a
lifetime.
In a study published online in
Genome Research, researchers have for the first time shown that the environment
experienced in the womb defines the newborn epigenetic profile, the chemical
modifications to DNA we are born with, that could have implications for disease
risk later in life.
Epigenetic tagging of genes by a
chemical modification called DNA methylation is known to affect gene activity,
playing a role in normal development, aging, and also in diseases such as diabetes,
heart disease, and cancer. Studies conducted in animals have shown that the
environment shapes the epigenetic profile across the genome, called the
epigenome, particularly in the womb. An understanding of how the intrauterine
environment molds the human epigenome could provide critical information about
disease risk to help manage health throughout life.
Twin pairs, both monozygotic (identical) and
dizygotic (fraternal), are ideal for epigenetic study because they share the
same mother but have their own umbilical cord and amniotic sac, and in the case
of identical twins, also share the same genetic make-up. Previous studies have
shown that methylation can vary significantly at a single gene across multiple
tissues of identical twins, but it is important to know what the DNA
methylation landscape looks like across the genome.
In this report, an international
team of researchers has for the first time analyzed genome-scale DNA methylation
profiles of umbilical cord tissue, cord blood, and placenta of newborn
identical and fraternal twin pairs to estimate how genes, the shared
environment that their mother provides and the potentially different
intrauterine environments experienced by each twin contribute to the epigenome.
The group found that even in identical twins, there are widespread differences
in the epigenetic profile of twins at birth.
"This must be due to events
that happened to one twin and not the other," said Dr. Jeffrey Craig of
the Murdoch Childrens Research Institute (MCRI) in Australia and a senior
author of the report. Craig added that although twins share a womb, the
influence of specific tissues like the placenta and umbilical cord can be
different for each fetus, and likely affects the epigenetic profile.
Interestingly, the team found
that methylated genes closely associated with birth weight in their cohort are
genes known to play roles in growth, metabolism, and cardiovascular disease,
lending further support to a known link between low birth weight and risk for
diseases such as diabetes and heart disease. The authors explained that their
findings suggest the unique environmental experiences in the womb may have a
more profound effect on epigenetic factors that influence health throughout
life than previously thought.
Furthermore, an understanding of
the epigenetic profile at birth could be a particularly powerful tool for
managing future health. "This has potential to identify and track disease
risk early in life, said Dr. Richard Saffery of the MCRI and a co-senior author
of the study, "or even to modify risk through specific environmental or
dietary interventions."
More information: Gordon L, Joo JE, Powell
JE, Ollikainen M, Novakovic B, Li X, Andronikos R, Cruickshank MN, Conneely KN,
Smith AK, Alisch RS, Morley R, Visscher PM, Craig JM, Saffery R. Neonatal DNA
methylation profile in human twins is specified by a complex interplay between
intrauterine environmental and genetic factors, subject to tissue-specific
influence. Genome Res doi:
10.1101/gr.136598.111
Provided
by Cold
Spring Harbor Laboratory
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