What would Stuart Little make of it? Mice have been created whose brains are half human. As a result, the animals are smarter than their siblings.
The idea is not to mimic fiction, but to advance our understanding of human brain diseases by studying them in whole mouse brains rather than in dishes.
The altered mice still have mouse neurons – the “thinking” cells that make up around half of all their brain cells. But practically all the glial cells in their brains, the ones that support the neurons, are human.
“It’s still a mouse brain, not a human brain,” says Steve Goldman of the University of Rochester Medical Center in New York. “But all the non-neuronal cells are human.”
Goldman’s team extracted immature glial cells from donated human fetuses. They injected them into mouse pups where they developed into astrocytes, a star-shaped type of glial cell.
A battery of standard tests for mouse memory and cognition showed that the mice with human astrocytes are much smarter than their mousy peers.
In one test that measures ability to remember a sound associated with a mild electric shock, for example, the humanised mice froze for four times as long as other mice when they heard the sound, suggesting their memory was about four times better. “These were whopping effects,” says Goldman. “We can say they were statistically and significantly smarter than control mice.”
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