Week in Review: June 22–26

Neanderthal-human hybrid discovered; the neurobiology of fear behavior; and an insulin patch that responds to high glucose levels in mice

By | June 26, 2015

Neanderthal-human descendent sequenced

SVANTE PAABOA 40,000-year-old human carried 6-9 percent Neanderthal DNA in its genome, according to a study published this week (June 22) in Nature. This is about twice as much as all non-African humans harbor in their genomes today. Some of the Neanderthal DNA in the ancient human was found in three large chromosomal segments, suggesting an interbreeding event between modern humans and Neanderthals that occurred just four to six generations back.

“I think the conclusions are quite clear, and it’s really quite remarkable that they were lucky to find a hybrid that was so recent to be able to date it to a few generations back,” Rasmus Nielsen, a University of California Berkeley population geneticist who was not involved with the work, told The Scientist.

The neurobiology of fear

WIKIMEDIA, RAMAResearchers mapped the neural activity of mice exposed to an approaching object and found the nervous signal travels from the cells in the retina that perceive the threat to the superior colliculus of the midbrain. There, neurons expressing the calcium-binding protein parvalbumin (PV) relayed the signal to the parabigeminal nucleus (PBGN), which leads to the amygdala. Stimulation of the PV neurons in the superior colliculus or of the PBGN were sufficient to reduce a fear response—the mouse first attempted to escape but quickly froze. The researchers published their results in Science this week (June 25).

“To me that was a surprise—that [the neural signals] take so many stages to arrive at the fear place [the amygdala],” said Botond Roska of the Friedrich Meischer Institute for Biomedical Research in Basel, Switzerland, who was not involved in the study. “I thought that this pathway would be a more direct and specific connection because it must be [processed] very fast.”

“One of the big challenges in neuroscience is to understand the relationship between molecules, cells, [and] synapses on one hand, and microcircuit function and behavior on the other,” said neuroscientist Peter Jonas of the Institute of Science and Technology in Klosterneuburg, Austria, who was also not involved in the work. “It is nice to bridge these different levels and . . . this paper provides a nice example of how this is becoming possible.”

Smart insulin control

YANQI YEA microneedle patch containing nanoparticles that release insulin in response to high glucose levels in mice could one day help diabetic patients better manage their blood sugar levels, according to a study published this week (June 22) in PNAS. In a mouse model of type I diabetes, the patches kept glucose levels within a normal range for several hours.

“Our microneedles are smart microneedles. They can respond to glucose levels and respond at the right time,” study coauthor Zhen Gu, a biochemical engineer at the University of North Carolina at Chapel Hill (UNC), told The Scientist. “We are trying to mimic the function of the pancreatic beta cells.”

The nanoparticles coating the microneedles release insulin as a result of an enzyme called glucose oxidase, which consumes oxygen when activated in the presence of high glucose, and a compound called 2-nitroimidazole, which changes from hydrophobic to hydrophilic as oxygen levels drop. “[This approach] kind of opens up a new avenue,” said Danny Chou, a biochemist at the University of Utah who has also worked on insulin patches.

Other news in life science:

Ebola Drug Trial Terminated

Early analysis of TKM-Ebola-Guinea offers discouraging results, causing sponsors to end the Phase 2 trial.

Extra DNA Base Discovered

An epigenetic variant of cytosine is stable in the genomes of living mice, suggesting a possible expansion of the DNA alphabet.

Edible Marijuana Labels Wrong

The dosage information on 83 percent of 75 edible marijuana products legally sold in Seattle, San Francisco, and Los Angeles was incorrect.

Senate Panel OKs NIH Budget Boost

The $2 billion increase in federal funding for the National Institutes of Health would be the biggest in more than a decade.

Ravenous Invasive Worm Now in U.S.

Researchers have found the New Guinea flatworm, one of the world’s most invasive species, in Florida, putting native ecosystems at serious risk.

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