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Unzipped chromosomes pass on parental stress
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Stress is inherited via faulty DNA zip stressed cell. If that cell happens to be an egg or sperm, the altered chromatin will end up in every cell in any offspring. Ishii pinpointed this mechanism by altering fruit flies to give them a gene for red eyes. The gene was positioned so that it would be active only if chromatin was unzipped, making it easy to spot whether ATF-2 had been detached and the chromatin had been altered. Ishii put one generation of mutated fruit flies under stress by heating the eggs from which they hatched, or exposing the eggs to salty water. After they had matured to adulthood, he mated them with healthy flies and found that the unzipped chromatin – and red eyes – passed to the second, but not third generation. But when Ishii put both the first and the second generations under stress, the effects were
MUTANT fruit flies have helped solve one of the biggest puzzles in genetics: how the damaging effects of stress can pass down the generations to children and grandchildren. Stress is thought to cause “epigenetic” changes to genes, which do not alter the sequence of their DNA but instead leave chemical marks that dictate how active genes are. If mice are stressed for two weeks after birth, for example, their offspring will show signs of depression and anxiety, despite enjoying the –Poorer health for grand kids too– usual levels of maternal care. There is mounting evidence that common health problems including diabetes, obesity, mental illness and even feeling fear could be the result of stress on parents and grandparents. Until now no one has been able to identify changes in inherited “Once the protein is DNA that might explain how detached, the chromatin these effects are passed on. structure opens, activating Shunsuke Ishii at the Riken genes that were hidden” Tsukuba Institute in Ibaraki, Japan, and colleagues have now identified a plausible process. “We more prolonged, influencing not believe we can convince many just one but three subsequent sceptics by clarifying the generations (Cell, DOI: 10.1016/ mechanism,” says Ishii. j.cell.2011.05.029). His team discovered that He says that mammals have a chemical or environmental counterpart to ATF-2 called ATF-7. What do octopus and mammal eyes tell us stress detaches a protein called Last year, his team found that activating transcription factor 2 psychological stress could alter about repeated patterns in evolution? (ATF-2) from chromatin, the ATF-7 in mice, leading to changes What about hummingbirds and sunbirds? densely packed DNA that makes in chromatin. Ishii’s team still To find out visit www.mapoflife.org and up chromosomes. needs to do experiments to see if explore amazing cases of biological convergence ATF-2 behaves as a kind of these changes are heritable. zipper, keeping the chromatin “What’s really exciting is from throughout the living world. tightly bound. Once it is detached, that this study shows a clear the chromatin structure opens, molecular mechanism that activating genes that would responds to stress,” says Moshe normally stay hidden. Szyf, who researches the Crucially, the unzipped implications of epigenetics chromatin is inherited by all for cancer therapy at McGill C. CYRUS-KENT K. PETERS J. DERK OPOTERSER A. PINGSTONE descendants of the original University in Montreal, Canada. n Llimchiu 2008
C. Michael Hogan
Mdf 2006
MAP OF LIFE Jens Petersen
CONVERGENT EVOLUTION ONLINE
www.mapoflife.org
A. THORNTON
Eugene Richards/getty
Andy Coghlan
14 | NewScientist | 2 July 2011
Stress is inherited via faulty DNA zip stressed cell. If that cell happens to be an egg or sperm, the altered chromatin will end up in every cell in any offspring. Ishii pinpointed this mechanism by altering fruit flies to give them a gene for red eyes. The gene was positioned so that it would be active only if chromatin was unzipped, making it easy to spot whether ATF-2 had been detached and the chromatin had been altered. Ishii put one generation of mutated fruit flies under stress by heating the eggs from which they hatched, or exposing the eggs to salty water. After they had matured to adulthood, he mated them with healthy flies and found that the unzipped chromatin – and red eyes – passed to the second, but not third generation. But when Ishii put both the first and the second generations under stress, the effects were
MUTANT fruit flies have helped solve one of the biggest puzzles in genetics: how the damaging effects of stress can pass down the generations to children and grandchildren. Stress is thought to cause “epigenetic” changes to genes, which do not alter the sequence of their DNA but instead leave chemical marks that dictate how active genes are. If mice are stressed for two weeks after birth, for example, their offspring will show signs of depression and anxiety, despite enjoying the –Poorer health for grand kids too– usual levels of maternal care. There is mounting evidence that common health problems including diabetes, obesity, mental illness and even feeling fear could be the result of stress on parents and grandparents. Until now no one has been able to identify changes in inherited “Once the protein is DNA that might explain how detached, the chromatin these effects are passed on. structure opens, activating Shunsuke Ishii at the Riken genes that were hidden” Tsukuba Institute in Ibaraki, Japan, and colleagues have now identified a plausible process. “We more prolonged, influencing not believe we can convince many just one but three subsequent sceptics by clarifying the generations (Cell, DOI: 10.1016/ mechanism,” says Ishii. j.cell.2011.05.029). His team discovered that He says that mammals have a chemical or environmental counterpart to ATF-2 called ATF-7. What do octopus and mammal eyes tell us stress detaches a protein called Last year, his team found that activating transcription factor 2 psychological stress could alter about repeated patterns in evolution? (ATF-2) from chromatin, the ATF-7 in mice, leading to changes What about hummingbirds and sunbirds? densely packed DNA that makes in chromatin. Ishii’s team still To find out visit www.mapoflife.org and up chromosomes. needs to do experiments to see if explore amazing cases of biological convergence ATF-2 behaves as a kind of these changes are heritable. zipper, keeping the chromatin “What’s really exciting is from throughout the living world. tightly bound. Once it is detached, that this study shows a clear the chromatin structure opens, molecular mechanism that activating genes that would responds to stress,” says Moshe normally stay hidden. Szyf, who researches the Crucially, the unzipped implications of epigenetics chromatin is inherited by all for cancer therapy at McGill C. CYRUS-KENT K. PETERS J. DERK OPOTERSER A. PINGSTONE descendants of the original University in Montreal, Canada. n Llimchiu 2008
C. Michael Hogan
Mdf 2006
MAP OF LIFE Jens Petersen
CONVERGENT EVOLUTION ONLINE
www.mapoflife.org
A. THORNTON
Eugene Richards/getty
Andy Coghlan
14 | NewScientist | 2 July 2011