American Scientist

In this roundup, digital features editor Katie L. Burke summarizes notable recent developments in scientific research, selected from reports compiled in the free electronic newsletter Sigma Xi SmartBrief. Online: https://www.smartbrief.com/sigmaxi/index.jsp

New Gene Editing Technique

The gene editing technique CRISPR has rapidly advanced genomic engineering, but one of its downsides is that it can be prone to cut DNA in the wrong place. A more complicated gene editing technique was recently proposed that avoids CRISPR’s proclivity for cutting and thus has more control over off-target effects.

The technique shows promise for treating the common genetic disorder thalassemia, which is characterized by low levels of hemoglobin in the bloodstream. The method could also work for other genetic disorders caused by a single mutant allele. Researchers used synthetic genetic material called peptide nucleic acids (PNAs) that were designed to bind to a particular section of mouse DNA where the faulty coding for hemoglobin resides. Once a PNA binds there, it forms a bumpy triple helix, an anomaly that a cell’s repair machinery will cut away. The second stage of the technique is to deploy a DNA patch with the correct hemoglobin code that the repair machinery can insert. The technique only worked in a handful of cells, but that was enough to cure thalassemia in mouse models. The next step is to check how it might perform in humans.

Bahal, R., et al. In vivo correction of anaemia in β-thalassemic mice by γPNA-mediated gene editing with nanoparticle delivery. Nature Communications 7:13304 (October 26)

Great Apes and False Belief

A new study that involved eye tracking of great apes watching videos of an actor in a gorilla suit indicated that these primates can predict another’s behavior even when they know it is misguided, which could indicate the ability to recognize in others a false belief. Such an ability is a stage in the development of a theory of mind, a stage previously thought to be unique to humans. The videos adapted a technique that has been used to study false belief in infants and that tests whether study subjects anticipate where someone will look for an object or individual. The videos showed high-stakes scenarios, such as the actor in a gorilla suit attacking a researcher, then hiding in one of two hay bales, then leaving after the researcher leaves the scene. When the researcher returns with a big stick to look for the wayward gorilla, eye tracking showed that the bonobos, chimpanzees, and orangutans who watched the video would spend time looking at the hay bale where it had been hiding, predicting where the researcher would mistakenly look for it. This study prompted a debate among primatologists about false belief and what conclusions were appropriate to draw from the study. Nevertheless, all seem to agree that it demonstrates the promise of eye tracking methods in animal behavior research and the potential for mental continuity between humans and their close relatives.

Krupenye, C., F. Kano, S. Hirata, J. Call, and M. Tomasello. Great apes anticipate that other individuals will act according to false beliefs. Science 354:110–144 (October 7)

Deep-Sea Viruses Kill Archaea

On the deep sea floor, bacteria are more abundant than archaea, but the latter suffer viral infections twice as often. Nearly all mortality of these microbes in the deep sea is due to viral infections. Because of the deep sea’s vast scale—it constitutes more than 65 percent of the world’s surface and more than 90 percent of its biosphere—these archaea–virus relationships could have large effects on global biogeochemical cycles. For example, deep-sea deaths of bacteria and archaea release between 0.37 and 0.63 gigatons of carbon per year. Although little is known about deep-sea ecosystems, this study is an important advance in understanding their uniqueness and significance.

Danovaro, R., et al. Virus-mediated archaeal hecatomb in the deep seafloor. Science Advances 2:e1600492 (October 12)

Intermediate Jaw in Fish Fossil 

A new fossil find of an ancient lineage of fish is rewriting what we know and will teach about jaw evolution in vertebrates. The fish fossil is from a group called placoderms that has long been thought to be an anomalous lineage of armored, “jawless” bony fish that died out as bony fish with modern vertebrate jaws emerged and gave rise to subsequent lineages. One of the ways that modern vertebrates can trace their evolution is the consistency in the jaw bones in everything from goldfish to lizards to humans. But this recent fossil find of a 423-million-year-old placoderm species, Qilinyu rostrata, as well as a placoderm fossil reported in 2013, Entelognathus primordialis, show that there were placoderms that had jaw bones ancestral to modern vertebrates. These finds demonstrate an intermediate form between the jawless, toothlike plates of earlier placoderms and the three-boned jaw (composed of a maxilla, premaxilla, and dentary) of modern vertebrates.

Zhu, M., et al. A Silurian maxillate placoderm illuminates jaw evolution. Science 354:334–336 (October 21)

Paralyzed Monkeys Walk

Monkeys with spinal cord injuries were able to walk again when a wireless implant was placed in their brains, stimulating electrodes in their legs that recreate signals recorded from their brains. The animals regained the ability to coordinate their legs and bear weight on them. Two people with spinal cord injuries are now undergoing an adapted version of this treatment.

Capogrosso, M., et al. A brain–spine interface alleviating gait deficits after spinal cord injury in primates. Nature 539:284–288 (November 10)