By Sue Goetinck Ambrose for the Dallas Morning News. Thanks to
Robert J. Krakow
While the human DNA code is at the root of all body processes,
scientists are starting to appreciate that the code is coated with extra
biological instructions. Although studies involving this extra layer
information are in their infancy, there are tantalizing hints that this
emerging science of epigenetics may reach into many aspects of human life
and disease.
Some scientists believe that nutrition, cancer, in vitro
fertilization – even autism – may be among the arenas where epigenetics
plays a role.
Reported incidence rates have been rising for autism, a neurological
disorder that impairs communication and other social skills. Researchers
do not know the reason for the rise, but because autism runs in families, scientists have concluded that genes play a role in the disease.
But genetics may not tell the whole story.
Researchers at the Baylor College of Medicine in Houston and their
colleagues are proposing that epigenetic information -chemical changes
layered on top of the genetic code -may also be a factor.
The epigenetic idea centers on chemical flags, called methyl groups,
which cells attach to their DNA. These flags signal cells to activate or
silence genes.
Folic acid, a supplement found in prenatal vitamins and added to
flour, bread and other grain products, aids in adding these methyl groups
to DNA.
Folic acid supplements decrease the risk for neural tube defects in
developing babies. A report scheduled for presentation this week at the
annual meeting of the American Society of Human Genetics proposes that too
much folic acid in a pregnant woman’s diet may increase the risk for
autism.
The scientists, led by Baylor geneticist Dr. Arthur Beaudet, have proposed
that in autism, a gene on human chromosome 15 may not acquire the
appropriate pattern of methyl group flags.
This gene has been previously linked to Angelman syndrome, a
condition marked by mental retardation, certain traits of autism and other symptoms.
Other researchers stress that the Houston team’s idea is only a
hypothesis.
“I think it’s a very interesting idea,” said James Sutcliffe, a
human geneticist at Vanderbilt University in Nashville.
But, he noted, “it’s an intellectual construct right now for which
there’s really not much proof.”
Dr. Sutcliffe said he favors the idea that autism occurs when
someone inherits a set of genes that, together, increases the risk for the
condition.
Nonetheless, other research has hinted at a link between autism and
epigenetic problems, he said.
For instance, about 2 percent of children with autism inherit an
extra copy of a particular stretch of DNA from their mother. This stretch is
saddled with epigenetic information that influences how cells read the
DNA.