Hybrid brains were created from rat and mouse cells

For the first time, two teams of scientists have created hybrid brain tissue using cells from mice and rats. Although these two rodents may seem very close from the outside, they are actually two different species and therefore incompatible a priori.

Brains of mice and mice hybrids: what method is used?

Previous experiments have shown that it is possible to replace the pancreas in a mouse using rat stem cells, using a method called “Blastocyst complement. Using this technique, stem cells from one species are injected into a very small embryo (or “blastocyst”) of another species, where they develop and take on a lost function.

Based on this first experiment, scientists wanted to see if the same could work with brain tissue.

To do this, a team led by Professor Jun Wu developed a system capable of identifying the genes responsible for the development of different types of brain tissue. They then discovered that a gene called “Hesx1” was essential for proper development of the forebrain in mice, and thus blastocysts lacking this gene were produced. They then injected mouse stem cells into the blastocyst and were able to close the gap. The mouse brain then developed normally.

Although mice's brains are larger than mice's, this did not pose a problem. The hybrid brains grew at the same rate and size as the brains of non-hybrid mice, and the rat- and mouse-derived neurons were able to transmit signals to each other as if they both belonged to the same species.

Meanwhile, another research team led by Christine Baldwin used blastocyst supplements to restore neural circuits in the mouse's olfactory system.

Once again, the mice's brains developed correctly and at the usual rate. “You can see rat cells in almost the entire mouse brain, which was quite surprising to us.” Baldwin said. “This tells us that there are few barriers to input, and suggests that many types of neurons in mice can be replaced with similar neurons in mice.”

Rat-mouse hybrid brains: why?

These hybrid brains could ultimately be a tool in the search for new treatments against neurological diseases in humans.

“Our ambition now is to enrich pig organs with a certain percentage of human cells, with the aim of improving outcomes for organ recipients. There are still many technical and ethical challenges we must overcome before we can test this clinically.” Trials, concludes John Woo.

Both reports are posted in the cell.