When Cooperation Counts

Everybody knows the shortest distance between two points is a straight line, and now Harvard researchers have evidence that sperm have been taking the familiar axiom to heart.   Though competition among individual sperm is usually thought to be intense, with each racing for the chance to fertilize the egg, Harvard scientists say that in some species, sperm form cooperative groups that allow them to take a straighter path to potential fertilization.

A new study, conducted by Heidi Fisher, a postdoctoral student working in the lab of Hopi Hoekstra, the Alexander Agassiz Professor of Zoology in the Museum of Comparative Zoology, and postdoctoral student Luca Giomi, who works with L. Mahadevan, the Lola England de Valpine Professor of Applied Mathematics, professor of organismic and evolutionary biology, and of physics, shows that in Peromyscus maniculatus, a species of deer mouse known to be promiscuous, sperm clump together to swim in a more linear fashion. The study is described in a July paper in Proceedings of the Royal Society B.  “We generally think that each individual sperm cell swims its little heart out to get to the egg. But it had been discovered that, in at least a handful of organisms, sperm will cooperate and swim as a group,” said Hoekstra, who is also a professor of organismic and evolutionary biology.

The new paper builds on a 2010 study conducted in Hoekstra’s lab, which found that sperm cells preferentially clump with those produced by the same male. Spurred by that earlier paper, Mahadevan approached Hoekstra with the idea of creating a mathematical model to understand whether and how sperm received an advantage by forming groups.

Read the full article here.

Now Your Food Has Fake DNA In It

Like many novel technologies in this age of TED Talks and Silicon Valley triumphalism, synthetic biology—synbio for short—floats on a sea of hype. One of its founding scientists, Boston University biomedical engineer James Collins, has called it “genetic engineering on steroids.” Whereas garden-variety genetic engineers busy themselves moving genes from one organism into another—to create tomatoes that don’t bruise easily, for example—synthetic biologists generate new DNA sequences the way programmers write code, creating new life-forms.

It may sound like science fiction, but synbio companies have already performed modest miracles. The California-based firm Amyris, for example, has harnessed the technology to make a malaria drug that now comes from a tropical plant. In order to do this, company scientists leveraged the well-known transformative powers of yeast, which humans have used for millennia to turn, say, the sugar in grape juice into alcohol: They figured out how the wormwood tree generates artemisinic acid—the compound that makes up the globe’s last consistently effective anti-malarial treatment—and programmed a yeast strain to do the same thing.  And there could be more innovations on the horizon. In 2011, Craig Venter, the scientist/entrepreneur who spearheaded the mapping of the human genome, vowed to synthesize an algae that would use sunlight to unlock the energy in carbon dioxide. If successful, this attempt to replicate photosynthesis could transform CO2 from climate-heating scourge into a limitless source of energy. Synthetic biologists also aim to conjure up self-growing buildings, streetlight-replacing glowing trees, and medicines tailored to your body’s needs. No wonder the market for synbio is expected to reach $13.4 billion by 2019.

Read the full article here. 

Strongest Evidence Yet That Pygmies’ Short Stature Is Genetic

It’s not another tall tale: Evolutionary biologists have developed a new understanding of the genetic basis of short stature in humans. Also known as the pygmy phenotype, a study published Monday in the Proceedings of the National Academy of Sciences shows that this trait has evolved several times over the course of human history.

“We have found the strongest evidence yet that the pygmy phenotype is controlled by genetics,” said Luis Barreiro of the University of Montreal and the senior author of this recent study. Although height is a tremendously variable trait among humans, several rain forest-dwelling populations in Asia and Africa have been noted for their unusually short stature. The average height among Batwa men (60.1 inches, 152.9 centimeters) and women (57.4 inches, 145.7 centimeters) is significantly lower than in neighboring Bakiga men (65.1 inches, 165.4 centimeters) and women (61.0 inches, 155.1 centimeters).

Barreiro and colleagues gathered genetic data from the Batwa and Baka peoples, as well as from three neighboring agricultural groups of average height. When they scanned different regions of the genome, they found significant genetic differences among the Batwa and Baka in an area of the genome that is known to code for the receptors for human growth hormones. When the researchers looked more closely, they found that these genetic differences weren’t just random chance and that the first Batwa and Baka people just happened to be short. Instead, these genetic differences were somehow benefiting the individuals living in these rain forest environments. It’s an example of convergent evolution, Barreiro says, in that the same trait (short stature) evolved independently in several different populations.

The results will help provide an understanding not just of the pygmy phenotype, but also of the evolution of the tremendous amount of diversity in our species.

Read the full article here.

A Record Number of Out-of-State Students Brings Windfall for UC System

Human Biology and Society student featured in a recent LA Times article



Spread of Genes Implicated in Post-traumatic Stress Disorder

Most people gradually recover from trauma, but a small fraction of individuals develop post-traumatic stress disorder (PTSD) — prompting scientists to look for the biological underpinnings of this extreme response to traumatic situations such as warfare, car accidents and natural disasters. Research published on 11 August in Proceedings of the National Academy of Sciences identifies up to 334 genes that may be involved in vulnerability to post-traumatic stress in rats.

Most animal studies of stress use intense stimuli such as electric shocks, designed to produce large, group differences between exposed and unexposed animals. But Nikolaos Daskalakis and his colleagues tried a subtler approach to elicit a wide range of individual responses in rats that had all experienced the same trauma — more closely mimicking the variability of human responses to disturbing events. “We wanted to capture the differences between a susceptible individual and one that is not susceptible to the same experience,” says Daskalakis, a neuroendocrinologist at the Icahn School of Medicine at Mount Sinai in New York.

To probe the mechanisms that control trauma susceptibility, the researchers used DNA microarray technology to screen 22,000 genes in samples from the blood, and the amygdala and hippocampus — brain areas that are involved in fear and memory. In males and females, and across the different tissues, anywhere from 86 to 334 genes showed changes in expression levels that appeared to relate to extreme or minimal responsiveness. “It gives us insight into a genetic marker for PTSD susceptibility and potential treatments targeting activation of the glucocorticoid receptor as a part of therapy,” says David Diamond, a behavioural neuroscientist at the University of South Florida in Tampa. Finding better indicators for trauma susceptibility could help researchers to develop and monitor treatments, he says.

Read the full article here.

Can A New Species of Frog Have A Doppelganger? Genetics Say Yes

Recently, Malaysian herpetologist Juliana Senawi puzzled over an unfamiliar orange-striped, yellow-speckled frog she’d live-caught in swampland on the Malay Peninsula. She showed the frog to Chan Kin Onn, a fellow herpetologist pursuing his doctorate at the University of Kansas. They wondered—was this striking frog with an appearance unlike others nearby in the central peninsula an unidentified species?

Extensive genetic analysis performed in the lab of Rafe Brown, curator of herpetology at KU’s Biodiversity Institute, would determine whether the Malaysian frog was indeed new to science—genetically distinct from its doppelgänger on Siberut Island. “The lab is very high-tech and is able to run a number of different types of genetic analyses,” Chan said. “It’s also able to run the latest in cutting-edge genetic analysis called Next Generation Sequencing, which a lot of researchers are currently utilizing. We also have a very powerful bioinformatics lab that can analyze extremely large and computationally expensive datasets. The great thing about the lab is that we have the equipment and expertise to run everything from initial DNA extractions to the final data analyses without having to rely on any outsourcing.”

When testing was complete, the first hunch of the Malaysian team proved right: “Sure enough, results from Rafe’s genetic analysis showed that the frog from Peninsular Malaysia was genetically too distant from the Siberut Island Frog to be considered the same species, so we decided to describe it as a new species.”

Read the full article here.

Human Brain Subliminally Judges ‘Trustworthiness’ of Faces

The human brain can judge the apparent trustworthiness of a face from a glimpse so fleeting, the person has no idea they have seen it, scientists claim.

Researchers in the US found that brain activity changed in response to how trustworthy a face appeared to be when the face in question had not been consciously perceived. Scientists made the surprise discovery during a series of experiments that were designed to shed light on the the neural processes that underpin the snap judgments people make about others. The findings suggest that parts of our brains are doing more complex subconscious processing of the outside world than many researchers thought. Jonathan Freeman at New York University said the results built on previous work that shows “we form spontaneous judgments of other people that can be largely outside awareness.”

The study focused on the activity of the amygdala, a small almond-shaped region deep inside the brain. The amygdala is intimately involved with processing strong emotions, such as fear. Its central nucleus sends out the signals responsible for the famous and evolutionarily crucial “fight-or-flight” response.

“The social cues for trustworthiness are considerably more subtle and complex than a simple, fearful expression on a clearly emotional face. It suggests that the amygdala’s processing of social cues outside awareness may be more extensive than we thought ,” Freeman said.

Read the full article here.

How Do You Make a Bird? Shrink a Dinosaur for 50 Million Years

Large flesh-eating dinosaurs evolved into small flying birds, but it did not happen overnight.

An international team of scientists on Thursday described an extraordinary evolutionary process that unfolded over a period of 50 million years in which a lineage of carnivorous dinosaurs shrank steadily and acquired numerous traits that led to the first appearance of birds.

The researchers, using techniques developed by molecular biologists to reconstruct virus evolution, examined 1,500 anatomical traits in 120 different dinosaurs from the theropod group. These bipedal meat-eaters included giants like Tyrannosaurus rex and Giganotosaurus as well as the lineage that produced birds. “Our study measured the rate of evolution of different groups of theropod dinosaurs,” said lead researcher Michael Lee, a paleontologist at the University of Adelaide and the South Australian Museum. “The fastest-evolving group also happened to be ancestral to birds. So, ultimately, the most adaptable dinosaurs proved to be the best long-term survivors, and surround us today in their feathered splendor,” Lee explained.

Read the full article here.