Not sure what the benefit is of a mouse not fearing a cat, I would guess that that type of fearlessness would lead to a lot of mouse deaths. But, here’s the stuff:

A team of University of Tokyo researchers led by professors Hitoshi Sakano and Ko Kobayakawa have announced they have genetically engineered a mouse that does not fear cats, simply by controlling its sense of smell. By tweaking genes to disable certain functions of the olfactory bulb — the area of the brain that receives information about smells directly from olfactory receptors in the nose — the researchers were able to create a “fearless” mouse that does not try to flee when it smells cats, foxes and other predators.

Read the rest here.