Starving pregnant mice can cause changes in sperm of her son who apparently distort the health of her grandchildren children, according to a new study. The discovery provides some of the strongest evidence yet that the environment of the mother during pregnancy can alter the expression of the DNA in ways that are passed on to future generations.
A number of studies have suggested that environmental constraints in a parent can affect the health of future generations. For example, women who were pregnant during a famine in 1944 in the Netherlands known as the Dutch hunger winter had children and grandchildren who were abnormally small or prone to diabetes and the obesity. Animal studies have also found that stress to a parent, such as exposure of pregnant mice to toxic chemicals or slightly shocking mouse father to smell fear, may cause effects such as infertility or behavioral changes that persist for two generations or more can not be explained by genetic mutations.
Some scientists suspect that the effects are mediated by so-called epigenetic changes, chemical modifications of DNA that can turn genes on or off. A team led by geneticist Anne Ferguson-Smith of the University of Cambridge in the UK and diabetes researcher Mary-Elizabeth Patti of Harvard Medical School explored this idea by studying the DNA of two generations of mice descended from a mother undernourished.
researchers gave pregnant mice chow containing only half the calories they need during the last week of gestation, a time when crucial epigenetic patterns in the sperm of a male embryo is erased then reset. As the group of Patti had shown previously, this treatment resulted in the offspring and grandchildren who were underweight and prone to diabetes.
The group then examined the DNA of the sperm of the males born hungry mothers. Compared to control mice son, their semen had fewer chemical tags known as methyl groups on about 110 DNA segments. Often, methyl were missing the genes involved in the metabolism relatives who can play a role in obesity and diabetes. The expression of these genes was also altered in some body tissues.
However, although fetal tissues grandchildren mother mice also had similar changes in gene expression, surprisingly, the DNA in those tissues were not wearing these differences in methylation. This suggests that changes eventually disappear, the team announced today online Science . Ferguson-Smith thinks changes in methylation in the sperm son reflect the legacy of his under-nutrition in the womb, but because they do not persist, do not directly explain the disease grandchildren. Methylation brands "are not the long-term memory that connects one generation to the disease to another," she said.
"This is a beautiful study" linking the ancestral exposures epigenetic changes, "but I don 't say that the book is closed on how these things work," says epigenetics Oliver Rando researcher of University of Massachusetts Medical School in Worcester. to show that these methylation patterns cause the health effects observed in the son of men and their offspring, must artificially turn on or off the suspect genes and show that this leads to the same result he said. "Disrupting the epigenome is the great challenge for the field."
in addition, the study does not rule out that the DNA methylation patterns are inherited from generations because researchers are not looking for them in the sperm of small-son says Rando.
Some are skeptical. Columbia University geneticist Timothy Bestor has "a number of issues" with the study. of these is that instead of studying inbred mice that are genetically identical, the researchers used a strain in which each mouse genetically variable. While this may have made the most similar mouse to the human population, it raises the possibility that in the womb, only fetal mice with a specific genetic makeup may have survived famine. Because the genetic also shapes methylation patterns, these genetic differences could be the reason why their sperm DNA methylation patterns different from those of control mice, Bestor said not because malnutrition directly modified patterns.
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