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Mouse study fingers potential cause of fertility problems, proposing obesity and egg quality link.

When a person dies from cancer, the culprit is usually not the original tumor but rather the cancerous cells that spread throughout the body and replicate in distant organs, a process called metastasis. Researchers have long known that metastasizing cancer cells slip their bonds and avoid immune detection by altering the sugars on their surfaces. They've even come up with a would-be drug to prevent such sugar alterations. But that compound interferes with needed sugars on normal cells, too, with lethal results in animals. Now, Dutch researchers report that they've packaged the drug in nanoparticles targeted exclusively to cancer cells, and they've shown that this combination prevents cancer cells from metastasizing in mice.  

Human-engineered microbes are workhorses of the pharmaceutical and chemical industries, churning out biofuels, drugs, and many other products. But they can cause big problems if they become contaminated by other microbes or viruses or escape into the environment. Now, a new type of microbe that can survive only on artificial nutrients promises better security against such mishaps. The strategy, described in two papers in this week's issue of Nature, might ultimately be used to control genetically engineered plants or other organisms released into the wild to create products or clean up pollution.

The United States is now experiencing what promises to be one of the worst outbreaks of measles since the virus was declared eliminated from the country in 2000.  It began in early January at Disneyland Resort in Anaheim, California, and has since spread to 14 states and infected 84 people, according to the U.S. Centers for Disease Control and Prevention (CDC). Measles, caused by a paramyxovirus from the genus Morbillivirus, is one of the most contagious diseases in the world, infecting more than 90% of susceptible hosts that come in contact with an afflicted individual. In the absence of widespread vaccination, the average person with measles will infect an average of 12 to 18 other people; in contrast, Ebola is typically transmitted to 1.5 to 2.5 people.

Nearly all U.S. senators agreed today on a measure affirming that climate change is real and not a hoax-including, to the surprise of many observers, Senator James Inhofe (R-OK), the man who once declared global warming a hoax. Meanwhile, although two other measures stating that humans are contributing to climate change won a majority of votes from the 99 senators present, they failed to garner the 60 votes needed to be adopted by the Senate.

Life on Earth is intimately connected to the natural cycles of light and dark that make up a 24-hour day. For plants, animals, and even bacteria, these circadian rhythms control many biological functions. Humans can overrule their body clocks, but at a price: People whose circadian rhythms are regularly disrupted-by frequent jet lag or shift work, for example-are more vulnerable to diabetes, obesity, cardiovascular disease, and cancer. There are various theories to explain these associations, and researchers now have a new player to consider: the bacteria that live in the digestive tract. According to a study in mice and a small group of human volunteers, the internal clocks of these gut microbes sync up with the clocks of their hosts. When our circadian rhythms get out of whack, so do those of our bacteria.

In the animal kingdom, humans are known for our big brains. But not all brains are created equal, and now we have new clues as to why that is. Researchers have uncovered eight genetic variations that help determine the size of key brain regions. These variants may represent "the genetic essence of humanity," says Stephan Sanders, a geneticist and pediatrician at the University of California, San Francisco, who was not involved in the study. These results are among the first to come out of the ENIGMA (Enhancing Neuro Imaging Genetics through Meta-Analysis) collaboration, involving some 300 scientists from 33 countries. They contributed MRI scans of more than 30,000 people, along with genetic and other information, most of which had been collected for other reasons. "This paper represents a herculean effort," Sanders says.

When it comes to charting the tree of life, the most important difference between humans and sharks isn't limbs versus fins or even lungs versus gills. It all comes down to our skeletons. Sharks' skeletons are made of cartilage, placing them along with rays and skates in a group of jawed vertebrates called cartilaginous fish. Humans-along with most other living vertebrates-belong to the same group as bony fish, whose skeletons are made of bone. Scientists knew that these groups diverged more than 420 million years ago, but what the last common ancestor looked like remained a mystery. Now, new discoveries inside the head of a small fossil fish from Siberia may provide some clues.

2014 was a banner year for making automotive fuel from nonfood crops, with a series of major new production plants opening in the United States. However, producing this so-called cellulosic ethanol remains considerably more expensive than gasoline. So researchers are always on the lookout for new ways to trim costs. Now they have a new lead, a microbe that can use abundant nitrogen gas as the fertilizer it needs to produce ethanol from plants.

Call it a scientific oddity-or a medical miracle. A girl who grew up with a serious genetic immune disease was apparently cured in her 30s by one of her chromosomes shattering into pieces and reassembling. Scientists traced the woman's improvement to the removal of a harmful gene through this scrambling of DNA in one of her blood stem cells-a recently identified phenomenon that until now had only been linked to cancer.

When scientists first made contact with an isolated village of Yanomami hunter-gatherers in the remote mountains of the Amazon jungle of Venezuela in 2009, they marveled at the chance to study the health of people who had never been exposed to Western medicine or diets. But much to their surprise, these Yanomami's gut bacteria have already evolved a diverse array of antibiotic-resistance genes, according to a new study, even though these mountain people had never ingested antibiotics or animals raised with drugs. The find suggests that microbes have long evolved the capability to fight toxins, including antibiotics, and that preventing drug resistance may be harder than scientists thought.

Its accuracy has made DNA evidence virtually unassailable. A landmark report published by the National Research Council in 2009 dismissed most forensics as unproven folk-wisdom but singled out DNA as the one forensic science worthy of the name. Yet in recent years Hampikian and other geneticists have begun to question the technology. Thanks to a series of advances-including the polymerase chain reaction, which can multiply tiny amounts of DNA-it's now possible to detect DNA at levels hundreds or even thousands of times lower than when DNA fingerprinting was developed in the 1980s. Investigators can even collect "touch DNA" from fingerprints on, say, a glass or a doorknob. A mere 25 or 30 cells will sometimes suffice. This heightened sensitivity can easily create false positives

Gut microbes-the collection of bacteria and other organisms that inhabit our intestines-have been shown to play a role in a wide variety of conditions from asthma to obesity. But researchers still don't know precisely how they contribute to obesity. To gain a better understanding, a team led by physiologist Mirko Trajkovski from the University of Geneva in Switzerland has been following up on any leads he can to learn about the link between these microbes and metabolism. Trajkovski knew from past research that getting rid of some gut bacteria in mice makes them less able to maintain their internal body temperature in the cold. He wondered whether there might be a connection between gut microbes, external temperature, and weight control.

Men, your sperm know how heavy you are. A new study reveals that sperm carry different chemical tags on their DNA depending on whether their owner is lean or obese. The findings suggest that men may be able to pass information about the availability of food in their environment down to their offspring, which could influence their child's odds of being overweight.

Why are millions of people allergic to peanuts or pollen, but hardly anyone seems to have a reaction to rice or raisins? Because only some of these things carry molecules similar to those found in parasites that send our immune systems into hyperdrive, according to a new study. The advance could help researchers predict what other foods might cause allergies.

The war against malaria has a new ally: a controversial technology for spreading genes throughout a population of animals. Researchers report today that they have harnessed a so-called gene drive to efficiently endow mosquitoes with genes that should make them immune to the malaria parasite-and unable to spread it. On its own, gene drive won't get rid of malaria, but if successfully applied in the wild the method could help wipe out the disease, at least in some corners of the world. The approach "can bring us to zero [cases]," says Nora Besansky, a geneticist at the University of Notre Dame in South Bend, Indiana, who specializes in malaria-carrying mosquitoes. "The mosquitos do their own work [and] reach places we can't afford to go or get to."

In just 15 years, the lizards' heads have grown larger-an adaptation that allows them to eat a wider assortment of insects made available by the dam's creation. The find may portend other rapid evolutionary changes across the globe as humans continue to dramatically alter the natural landscape.  

Almost 80% of all antibiotics in the United States aren't taken by people. They're given to cows, pigs, and chickens to make them grow more quickly or as a cheap alternative to keeping them healthy. These drugs could give rise to superbugs-bacteria that can't be treated with modern medicine-and things are only getting worse. In 2013, more than 131,000 tons of antibiotics were used in food animals worldwide; by 2030, it will be more than 200,000 tons. In a paper published today in Science, epidemiologist Thomas Van Boeckel of the Swiss Federal Institute of Technology in Zurich and colleagues outline the growing threat-and what can be done about it. Boeckel spoke to us about his team's work. This interview has been edited for clarity and length.