Chemotherapy is poison that happens to kill cancer cells faster than it kills healthy cells; that it wreaks havoc on the bodies of patients is unsurprising. But chemo may also affect their unborn children. According to a new study in PNAS, the offspring of mice treated with chemotherapy have higher rates of mutation, even though the offspring themselves were never exposed to the drugs.
The results suggest that these mutations arise from genome destabilization caused by exposure to chemo, rather than just mutated sperm from the treated father. Male mice in the study were exposed to one of three common anticancer drugs—cyclophosphamide, mitomycin C, or procarbazine—and then allowed to mate with untreated females. After sequencing a small piece of DNA from the offspring, the researchers found that mice with treated fathers had mutation rates up to twice that of mice with untreated fathers. Notably, these mutations were present in DNA inherited from both the treated father and untreated mother.
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What’s the News: We’ve long had signs that when it comes to inheritance, DNA isn’t the be-all, end-all. Trees that have the exact same genes but were raised in different greenhouses behave differently. Worms with genes that impart long life can pass on that longevity to their progeny—even if they don’t pass on the genes. Both of these phenomena, we’ve discovered, come from epigenetic changes in tags attached to DNA that control whether genes get expressed.
But every now and then we get a whiff of other possible routes for inheritance, even stranger than that. A new paper in Cell reports that worms whose grandparents had the ability to fight viruses using a fleet of tiny RNA molecules retain these molecules even when they don’t have the genes for them. They can pass these molecules down for more than a hundred generations.
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Nematode worms live longer if their grandparents had particular genes.
But they don’t need to receive the genes themselves to feel the effects.
What’s the News: Scientists have discovered that worms who’ve been given mutated genes that let them live longer pass on their longevity to their descendants—even when the descendants don’t receive the genes. How does it work?
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RNAs from rice can survive digestion and make their way into mammalian tissues, where they change the expression of genes.
What’s the News: It’s no secret that having lunch messes with your biochemistry. Once that sandwich hits your stomach, genes related to digestion have been activated and are causing the production of the many molecules that help break food down. But a new study suggests that the connection between your food’s biochemistry and your own may be more intimate than we thought. Tiny RNAs usually found in plants have been discovered circulating in blood, and animal studies indicate that they are directly manipulating the expression of genes.
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Children of older mothers, scientists have long known, are at higher risk for certain genetic disorders such as Down syndrome. But the father’s age is matters, too. As a father’s age increases, research shows, so does his child’s risk of mental illness, schizophrenia and autism in particular. In Scientific American, Nicole Grey explores the link between a father’s age and his child’s health, as well as the tricky questions about what mechanisms are behind the that link: genes, epigenetic changes, environment, or some combination of the three.
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All clones are not alike.
What’s the News: Foresters have long noticed that trees with the exact same genes, when raised in separate nurseries, have very different responses to drought. While one shoots up through lean times, the other droops. Why the divergence?
Scientists have now found that twin trees raised separately are, just like human twins, expressing different genes. In other words, nurture is affecting nature.
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What’s the News: While you may be able to hide your age with makeup and plastic surgery, don’t think that your deception is foolproof. Researchers have now developed a technique to ascertain your age to within five years using only your saliva. The new method, published in the journal PLoS One, could someday be used by forensic experts to pinpoint the age of crime suspects.
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What’s the News: Researchers have known for decades that what a woman eats during her pregnancy can impact her child’s weight later in life. Now, a new study shows a possible mechanism for how mom’s diet affects baby’s weight: Epigenetic changes—changes that can increase or decrease the expression of a particular gene but don’t alter the genetic sequence—to a gene involved in fat metabolism can be passed from mother to child during pregnancy.
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Smoke is in the air again. Well, smoking, rather. The newest report by the Surgeon General (yes, they’re still doing those) came out this week, and the 30th installment of this institutional dispatch ratcheted up the message. It’s not just a lot of smoking that will kill you; the Surgeon General’s office is now pushing the idea that even one cigarette is one too many—serious damage can start immediately, says the report.
Thursday’s report says there’s no doubt that tobacco smoke begins poisoning immediately — as more than 7,000 chemicals in each puff rapidly spread through the body to cause cellular damage in nearly every organ. “That one puff on that cigarette could be the one that causes your heart attack,” said Surgeon General Regina Benjamin. [AP]
It’s not exactly a revelation that smoking is risky and get riskier the more you do it. However, this is the first in the long line of these reports to really press the points that have turned up in recent research, like epigenetic changes or immediate risk to the cardiovascular system.
The root of the problem is that even small amounts of the chemicals in cigarette smoke cause rapid inflammation in the endothelium, or lining, of blood vessels and in the lungs. Inflammation is increasingly blamed by researchers as a key promoter of blood vessel plaques and clots and in obstructive lung diseases like emphysema. “The evidence on the mechanisms by which smoking causes disease indicates that there is no risk-free level of exposure to tobacco smoke,” the report concludes. [WebMD Health News]
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Scientists knew that overweight mothers tend to have more overweight children. But is the same true for fathers? This week in Nature, Margaret Morris and her team demonstrated this effect in male rats, the first time it’s been shown to work in males. The findings are another example of how non-genetic factors, like how much a parent eats, can have a biological impact on offspring.
The researchers put one of their two groups of male rats on a high-fat diet, the other on a normal one. Unsurprisingly, the high-fat rats put on a lot of weight and began to show symptoms of type II diabetes, like insulin resistance and struggles with metabolizing glucose. And then there were their kids:
The real surprise came when Morris’s team went on to examine the obese rats’ female offspring. These too had problems regulating insulin and glucose levels. The healthy fathers, however, had correspondingly healthy daughters. Whether similar defects emerge in sons remains to be seen. [Nature News]
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What does it take to be a long-living queen? Change your gene expression, say researchers who analyzed both worker ant and queen ant genes in two ant species–making the humble bug the second social insect (after the bee) to get sequenced.
Their results appear today in Science and suggest that epigenetic changes–molecular switches that alter gene expression–may mean the difference between the queen’s long life, and the workers’ short one. Epigenetic changes don’t actually modify the underlying genetic code, instead they’re carried out by mechanisms that act like on and off switches for genes. That could explain how a queen and worker ant can have the same genetic blueprints but very different lives.
“Ants are extremely social creatures and their ability to survive depends on their community in a very similar way to humans,” says [co-author Danny] Reinberg, who is also a member of the NYU Cancer Institute. “Whether they are workers, soldiers or queens, ants seem to be a perfect fit to study whether epigenetics influences behavior and aging.” [Arizona State University]
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Addiction researchers constantly wade through the ways that drugs like cocaine change your brain, and a new study in Science has pointed to a new epigenetic factor. Cocaine, the researchers say, can scramble the way genes turn on and off in a key brain region associated with pleasure and reward.
Ian Maze said his team gave one group of mice repeated doses of cocaine and other group repeated doses of saline with just one blast of cocaine at the end to study the differences. The team paid particular attention to a protein called G9a, whose behavior in the nucleus accumbens region of the brain seems to be altered by cocaine use. The role of the protein appears to be to shut down genes that shouldn’t be on. One-time use of cocaine increases levels of G9a. But repeated use works the other way, suppressing the protein and reducing its overall control of gene activation [TIME]. The researchers found that the overactive genes caused brain cells in the region to grow more connections to each other. The growth of such neural connections can reflect learning. But in the case of addiction, that may involve learning to connect a place or a person with the desire for more drugs [TIME].
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Victims of child abuse may bear chemical marks on their genomes that alter the way they respond to stress as adults, according to a small study. Researchers say they detected changes, almost like genetic scars, to a region of the genome that either promotes or tamps down the expression of a certain gene involved in stress responses. This could help explain why childhood abuse, such as sexual abuse or neglect, can cause depression, other mental health effects and suicide, and could some day lead to treatments to help victims overcome their abusive childhoods [Reuters].
Researchers studied 36 brain samples from the Quebec Suicide Brain Bank: 12 from suicide victims who had been abused as children, 12 from suicide victims that suffered no known abuse, and a final 12 who died suddenly in accidents. They found that only the brains of abuse victims showed the changes.
The results are the latest exciting findings in the young field of epigenetics, the process by which environmental factors can alter the expression of genes. In epigenetic changes, the DNA sequence itself isn’t altered, but other mechanisms change certain genes’ activities. Psychiatrist Jonathan Mill says of the new study: “Whilst these results obviously need to be replicated, they provide a mechanism by which experiences early in life can have an effect on behaviour later in adulthood. The exciting thing about epigenetic alterations is that they are potentially reversible, and thus perhaps a future target for therapeutic intervention” [BBC News].
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