Rat Nurture Affects DNA of "Children"

Guys... This is potentially very important research! I have read some research reports in which environment seemed to become part of the genetic inheritance of organisms. This is another such account.

Might the Nature vs Nurture vs Genetics battle continue at cocktail parties everywhere in the world until the end of time!

Pooch

STROKE the belly of a newborn female rat for a few hours a day and chemical "caps" will appear on its DNA that make its brain look more like that of a male.

This extraordinary finding suggests that some biological differences between male and female brains may not be decided during fetal development, but instead appear after they are born.

According to traditional thinking, sex-specific differences in mammals are determined in the womb by genes on the X and Y chromosomes, with the prenatal hormones the fetus is exposed to also playing a role.

Recently, however, it has become clear that the behaviour of a mother rat towards her offspring can cause sex-specific changes. For example, mother rats spend more time licking and grooming their sons, which previous studies suggest is necessary for their genitalia to form properly.

To see if a mother's touch might also cause sex-specific changes in rats' brains, Anthony Auger at the University of Wisconsin, Madison, and colleagues stroked baby female rats, giving them the attention normally reserved for males. They found that the number of oestrogen receptors in the hypothalamus of stroked females was lower than in unstroked females, and similar to levels found in males.

When the team examined the brains more closely, they noticed that the pattern of chemical caps called methyl groups that sit on DNA resembled that found in males, with more caps on the gene that codes for oestrogen receptors. As the caps reduce gene expression, this higher number of methyl groups is likely to be responsible for the decrease in oestrogen receptors.

As methylation is often permanent, the methylation patterns caused by a mother's stroking may also be long lasting, says Auger, who presented the findings at the Society for Neuroscience meeting in Washington DC in November.

Methylation is "a short cut, a way for organisms to reduce the amount of information they have to encode in their genome," says Julie Markham of the University of Maryland School of Medicine in Baltimore.

This is the first time that "epigenetic" influences outside of the womb have been linked to sex differences in mammals.
http://www.newscientist.com/article/mg20126903.300-mums-behaviour-may-make-young-rats-more-butch.html?DCMP=OTC-rss&nsref=life

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