Mouse-rat hybrid has neurons of both species in its brain

Amazing stuff! This may have huge implications!

"Researchers in the US are the first to successfully create hybrid brains of 2 different species using a technique called blastocyst complementation. ...
the team has created mice that can sense odours with their rat neurons, which successfully integrated into part of the olfactory system. ..."

"... It is the first time that an animal has been able to use the sensory apparatus of another to sense and respond accurately to the world and is one indication of how flexible the brain can be in integrating outside brain cells. ..."

From the highlights and abstract:

"Highlights

• Rat stem cells develop in mouse blastocysts to broadly populate two-species brains

• Rat neurons develop synchronously and synapse with cognate mouse neurons

• Genetic models of circuit loss or silencing unveil rescue capacity of exogenous neurons

• Rat sensory neurons restore the primal behavior of food seeking to anosmic mice

Summary

A central question for regenerative neuroscience is whether synthetic neural circuits, such as those built from two species, can function in an intact brain. Here, we apply blastocyst complementation to selectively build and test interspecies neural circuits. Despite approximately 10–20 million years of evolution, and prominent species differences in brain size, rat pluripotent stem cells injected into mouse blastocysts develop and persist throughout the mouse brain. Unexpectedly, the mouse niche reprograms the birth dates of rat neurons in the cortex and hippocampus, supporting rat-mouse synaptic activity. When mouse olfactory neurons are genetically silenced or killed, rat neurons restore information flow to odor processing circuits. Moreover, they rescue the primal behavior of food seeking, although less well than mouse neurons. By revealing that a mouse can sense the world using neurons from another species, we establish neural blastocyst complementation as a powerful tool to identify conserved mechanisms of brain development, plasticity, and repair."

Mouse-rat hybrid has neurons of both species in its brain

With Hybrid Brains, These Mice Smell Like a Rat (original news release)

Functional sensory circuits built from neurons of two species (open access)

Graphical abstract

Mouse hippocampus with rat cells (red) and nuclei of both mouse and rat cells (blue). 

Mice that smell like a rat. In the hybrid brains, odor processsing centers (circular structures) are a mixture of rat and mouse neurons. Odor processing centers with red cells contain rat neurons; odor processing centers with green neurons contain mouse neurons.