Mom's Care Can Alter DNA of Her Offspring
- Mellow or Stressed?
Mom's Care Can Alter
DNA of Her Offspring
Wall Street Journal Science Page
July 16, 2004
If anyone out there still believes that DNA is destiny and that
claims to the contrary are so much bleeding-heart, PC drivel (my
favorite is that parents' treatment of their children has no effect
on their character, beliefs, behavior or values), neuroscientist
Michael Meaney has some rats he'd like you to meet.
Since the 1990s, he and his colleagues at McGill University,
Montreal, have been documenting how mother rats affect their
offspring (dads don't stick around to raise the kids). Now they have
scored what neuroscientist Robert Sapolsky of Stanford University,
Palo Alto, Calif., calls "a tour de force": proof that a mother's
behavior causes lifelong changes in her offspring's DNA.
A decade ago Prof. Meaney noticed that newborn rats whose mothers
rarely lick and groom them grow up... well, there is a fancy
biochemical description for it, but let's just say that they grow up
a bit of a neurotic mess. Pups of attentive moms grow up less
fearful, more curious, mellower.
Prof. Meaney and his team then showed that this wasn't a case of
mellow moms having mellow kids and neglectful moms having maladjusted
kids, as the DNA-as-destiny crowd would have it. When the scientists
switch around the newborns so that rat pups born to attentive moms
are reared by standoffish moms, the pups grow up to be extremely
stressed out, nearly jumping out of their skins at the slightest
stress. Pups born to standoffish moms but reared by attentive ones
grow up to be less fearful, more curious, more laid-back, taking
stress in stride.
Rearing, it turns out, affects molecules in the brain that catch hold
of stress hormones. Licking and grooming increases the number of
these receptors. The more such receptors the brain has in the region
called the hippocampus, the fewer stress hormones are released; the
fewer the stress hormones coursing through its body, the mellower the
It turns out that all newborn rats have a molecular silencer on their
stress-receptor gene. In rats reared by standoffish mothers, the
silencer remains attached, the scientists will report in the August
issue of Nature Neuroscience. As a result, the brain has few stress-
hormone receptors and reacts to stress like a skittish horse hearing
But licking and grooming by an attentive mother literally removes the
silencer; the molecule is gone. Those baby rats have lots of stress-
hormone receptors in their brains and less stress hormone, and they
grow up to be curious, unafraid and able to handle stress.
"In the nature/nurture debate, people have long suspected that the
environment somehow regulates the activity of genes," says Prof.
Meaney. "The question has always been, how? It took four years, but
we've now shown that maternal care alters the chemistry of the gene."
The discovery overturns genetic dogma so thoroughly -- after all, how
mom treats the kids isn't supposed to alter something so fundamental
as their DNA -- that one researcher reviewing Prof. Meaney's
manuscript at a prominent American science journal said there is no
precedent for such a claim, asserted that he simply didn't believe
it, and recommended that the journal not publish it. The scientists
at Nature disagreed.
A key unanswered question is whether DNA can change even later in
life. That is, can rats who grow up to be skittish, because they were
reared by standoffish mothers, mellow out as the result of some
experience? And does parental care, or other experience, alter DNA in
It would be astonishing if it did not. Altering genes by adding or
removing silencing molecules is part of a new field called
epigenetics. If epigenetics were a film, it would be "Fahrenheit
9/11," the hot new release and one that is causing more than a bit of
consternation among traditionalists. This year's Nobel Symposium in
Stockholm featured epigenetics, as did the A-list annual conference
of the Cold Spring Harbor Laboratory in New York. Last month, the
National Institutes of Health announced a $5 million grant to Johns
Hopkins University School of Medicine, Baltimore, to establish the
Center for Epigenetics of Common Human Disease, the first of its kind.
Genetic changes are mutations in which one or more of the four
chemicals that make up the twisting double helix of DNA is,
typically, deleted or changed. Instead of ATTCTG, for instance, you
have ATTGTG; as a result, the gene no longer functions as intended.
Epigenetic changes, in contrast, leave the sequence of As, Ts, Cs and
Gs untouched. But the DNA acquires some new accessories, as it were:
Certain small molecules glom onto the DNA, and suddenly a gene that
was silent is active, or one that was active is hushed. That is what
happened to Prof. Meaney's rats: A previously silenced gene began
singing loud and clear.
The appeal of epigenetics is obvious to anyone who is or knows an
identical twin. Despite having the exact same sequence of DNA,
identical twins aren't identical, especially when it comes to
diseases such as cancers and mental illness. Something has altered
their DNA sequence so that disease-causing genes turn on or disease-
suppressing genes turn off. I'll explore epigenetics further in next
- Ok, first of all, the idea that experience shapes the brain
is not new. I posted http://www.violence.de on this list
years ago, for example. And you can go all the way back to
the Harlow monkey experiments.
Here's a book review that popped up recently:
Minding the baby
When researchers studied the brains of Romanian orphans -
children who had been left to cry in their cots from birth
and denied any chance of forming close bonds with an adult
- they found a "virtual black hole" where the orbitofrontal
cortex should have been.
Secondly: this writer seems confused about the meaning of
"epigenetic". As I understood it, what "epigenetic"
(ancient greek for "outside genetic") refers to is the
influence of the non-DNA material in the egg when it's
fertilized. In other words, the organism that you get is
not *just* the result of the DNA, but the result of the DNA
+ the rest of the egg. This writer seems to have confused
epigenic factors with gene *expression*. Genes control the
expression of other genes, so that depending on the
environmental circumstance, some genes may or may not be
expressed. One way this is done is by attaching other
molecules to the DNA (you could call them "silencers" but
I've never heard biologists use the term) which inhibit the
ribosomes from transcribing that section of the DNA.
On Mon, 19 Jul 2004 16:04:02 -0000, Michael Korns <mkorns@...> wrote:
> Mellow or Stressed?
> Mom's Care Can Alter
> DNA of Her Offspring
> Wall Street Journal Science Page
> July 16, 2004
- On Thu, 22 Jul 2004 Wayne Radinsky <waynerad@...> wrote
Subject: Re: Mom's Care Can Alter DNA of Her Offspring
I re-read the original article you posted. I also searched
Google news for more articles.
In the two articles (yours and the one I found on Google),
I did not see any evidence that the so-called "altered" DNA
affected the germline and was passed to offspring. I could
not find any evidence that the "epigenetic" factors -- the
"silencers" for "stress hormone receptor regulation" were
transported from the brain to the egg cells where they
could affect the offspring via epigenetic effects.
Therefore NO Lamarckian evolution is taking place.
Remember, to establish Lamarckian evolution, it is not
enough to show the mother's behavior affects the brain
development of the offspring. You must also show that those
changes are transmitted to the offspring's offspring.
You are right about the author's use of the term "epigenetic".
As for Lamarckian evolution taking place, we're getting closer.
Certainly, cloning is an example of indirect Lamarckian
evolution. The scientist's brain alters Dolly's genes and the
changes are passed on the Dolly's children. Furthermore, as
more experiments in somatic genetic treatments are successful,
the barriers to true Lamarckian evolution will be further
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