There is no use for that . . . the glowing that is. Glowing genes are used as 'markers' in most cases . . . they simply show the experiment worked. Its harmless to the animal, easily tested, and and reliable. (The Glofish were something of an exception . . . they were an more advanced technique and only glowed under particular conditions when they were first created . . . they altered them to glow under UV all the time when they started selling them as pets)
The purpose of the 'green glowing bunny' was the same (and by the way, she only glowed green under UV and only on exposed tissue like her nose . . . those green glowing rabbit pictures you've seen were the work of an artist . . .which is its own story). Since rabbits are used for medical research, I'm sure there was a good reason for a transgenic rabbit.
Now, WHY they want to make transgenic cats . . . I've heard about the knock-out cats that don't provoke allergic reactions. But that's taking a gene away, not adding one. I suppose you could use it to perfect your cloning of cats, but I have major issues with cloning pets (livestock is ok, in my mind). Cats aren't used much for reserarch, they are not livestock even where people eat them . . . So, if the question is, why do they want to make a transgenic cat, I have no idea. They want to make a glowing cat so they CAN make transgenic cats.
My guess though, would be they are going to perfect the cloning technique and then start selling designer cats with extra genes. I have no idea exactly what you'd want to add, except maybe color, but perhaps I lack imagination.
