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article imageScientists discover how we pass on DNA changes caused by stress

By Elizabeth Cunningham Perkins     Jun 27, 2011 in Health
Scientists have theorized the effects of stress could be passed to future generations through changes in gene expression that leave basic DNA structures intact. A new study has revealed an underlying, molecular-level cause operating within stressed cells.
Geneticist Shunsuke Ishii and his colleagues at RIKEN Tsukuba Institute recently announced they shed light on a complex cellular mechanism underlying stress-caused epigenetic changes that are transmitted to future generations without altering the genes' original DNA backbone of Adenine, Guanine, Thymine and Cytosine molecule sequences, according to their article, published in the June 24 issue of Cell, outlining new experiments on fruit flies (genus Drosophila).
According to the article abstract and other materials provided by Cell Press:
Gene expression of encoded proteins depends upon how genes are chemically repackaged into more complex chromatin structures. But in some sections of the genome, genes are repackaged extra-tightly into heterochromatin structures that are passed intact to the next generation, usually without any active genes.
The researchers had discovered 20 years ago in studies of the unicellular organism yeast that a gene known as activation transcription factor-2 (ATF-2) must be present for the tightly-wound heterochromatin packages of suppressed genes to form.
But they found environmental stress, inflammation and oxidative stress activated protein kinases (enzymes that modify protein production by adding a phosphate group), altering ATF-2 and disrupting heterochromatin formation in yeast cells.
To test if this mechanism also activates in multicellular organisms, the researchers turned to fruit flies, because, like yeast cells and humans, these rapidly gestating insects (and favorite genetic test-subjects) carry the ATF-2 gene.
From the new tests, they found that the ATF-2 gene changes and heterochromatin disruption also occurred in the fruit fly embryos exposed to experimental stresses, and found that this mechanism released the inactive genes (that would have remained silent within heterochromatin "packages"), modifying the genomic structure of the organisms, introducing changes that were passed to future generations.
However, these changes were transmitted in a non-Mendelian mode, and the defective heterochromatin gradually reverted to normal over multiple generations.
On the basis of this new research, the scientists speculated similar epigenetic changes in humans could result in inherited impairments in cellular function, metabolism and behavior, and corresponding predispositions to "lifestyle diseases," such as diabetes and heart disease and psychological disorders, such as schizophrenia.
But they also noted that drugs have already been developed that target the formation of the enzymes that altered the ATF-2 genes in the stressed-out yeast cells and fruit flies.
According to ScienceDaily, a recent survey of epigenetic research by theoretical evolutionary biologist Eva Jablonka of Tel Aviv University suggested that molecular-level effects from "traumatized" -- but not mutated or otherwise obviously altered -- DNA could be playing roles in many chronic conditions and ailments.
More about Epigenetics, Stress, Damaged dna, DNA damage stress
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