For millennia, scientists and philosophers have pondered what separates man from animal. Whether it was utilizing the mirror recognition test, examining ancient weapons and tools, or even looking into our own choices and decisions, we have always wondered what makes us so different.
So far, we have never displayed a trait that truly separates us from every animal. Ed Lein, an investigator at the Allen Institute for Brain Science, however, begs to differ. He believes that new advancements in biotechnology have given us the ability to look for differences in the human body, invisible to the naked eye.
“Studying the differences at the level of cells and circuits is a good place to start, and now we have new tools to do just that,” Lein said in a press release.
In a new study published in the journal Nature Neuroscience, Lein and his colleague Gábor Tamás, a neuroscientist at the University of Szeged in Szeged, Hungary, looked into cell environment and discovered a new type of human brain cell that has never been seen in mice or other well-studied laboratory animals.
The premise of the study was surprisingly simple. In the study, researchers used brain tissue samples from two 50-year-old men who had previously donated their bodies to research and examined the top layer of the cortex. The cortex is a part of the brain responsible for human consciousness and represents a distinct aspect of human anatomy that differs from other animals.
“It’s the most complex part of the brain, and generally accepted to be the most complex structure in nature,” Lein said when explaining why they chose this part of the body.
The two researchers did not initially work together. Tamás’ research lab in Hungary studied the human brain classically, by examining cell shapes and their electrical properties. Meanwhile, at the Allen Institute, Lein studied the brain through comparison, by exclusively focusing on what made human brain cells unique in comparison to mice brain cells. The two met at the Allen Institute, when Tamás was invited to present his research on different brain cells. Tamás and Lein quickly realized that they had in fact both discovered the same cell but in two completely different ways.
“We realized that we were converging on the same cell type from absolutely different points of view,” Tamás said, in the same interview with Science Today.
With this realization, the two decided to work together.
In collaboration, the two research teams found that “rosehip cells,” the unique brain cell in question, turn on a specific set of genes not found in other well researched animals. More specifically, the rosehip neuron has the ability to control information flow in a very specific way.
Tamás explained this phenomena by relating the cell to a car.
“This particular cell type — or car type — can stop at places other cell types cannot stop,” Tamás said. “The car or cell types participating in the traffic of a rodent brain cannot stop in these places.”
Tamás and Lein have used this information to see if the mouse is truly the best animal to test on in research. If rosehip neurons are potentially responsible for specific human brain disorders, then perhaps mice might not be the best candidates for research in brain disorders.
Dr. Trygve Bakken, a Senior Scientist at the Allen Institute for Brain Science and one of the authors of this study, addressed this rising concern by pointing out that human brains are not completely identical to mouse brains.
This may prove that attempting to replicate a human system in an animal system is harder than scientists previously believed.
