Smart mice with half-human brains created

LONDON: Researchers have created mice whose brains are half-human, making the animals smarter than their peers.

The altered mice still have mouse neurons – the “thinking” cells that make up around half of all their brain cells but all the glial cells in their brains, the ones that support the neurons, are human, researchers said.

“It’s still a mouse brain, not a human brain. But all the non-neuronal cells are human,” said Steve Goldman of the University of Rochester Medical Center in New York.

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.

Within a year, the mouse glial cells had been completely usurped by the human interlopers. The 300,000 human cells each mouse received multiplied until they numbered 12 million, displacing the native cells.

A battery of standard tests for mouse memory and cognition showed that the mice with human astrocytes are much smarter than their mousy peers, ‘New Scientist’ reported.

In another experiment, Goldman injected immature human glial cells into mouse pups that were poor at making myelin, the protein that insulates nerves.

Once inside the mouse brain, many of the human glial cells matured into oligodendrocytes, brain cells that specialise in making the insulating material, suggesting that the cells somehow detected and compensated for the defect.

This could be useful for treating diseases in which the myelin sheath is damaged, such as multiple sclerosis, said Goldman.

He has already applied for permission to treat MS patients with the glial progenitor cells, and hopes to start a trial in 12 to 15 months.

To explore further how the human astrocytes affect intelligence, memory and learning, Goldman is grafting the cells into rats, which are more intelligent than mice.

Goldman cautioned that the added cells do not provide the animals with additional capabilities that could in any way be ascribed or perceived as specifically human.

“Rather, the human cells are simply improving the efficiency of the mouse’s own neural networks. It’s still a mouse,” he said. — PTI