Legs? I'm guessing that isn't what the male mice will be saying.
A Dr. John Baker, who worked for the VA decades ago, wrote a book on how he was able to get different types of limbs to grow on salamanders using electrical signally. You send an electrical signal to grow such and such limb and that is what would happen to the salamanders.
Salamanders are unique, in that they can regrow different limbs and organs without to much difficulty. A salamander loses an eye for example it can regrow its eye. Humans and most animals on the other hand are typically only able to regrow a few areas in the body. For humans bones can typically regrow. Sometimes tragically bones will not heal and in those cases in the past the only option available was to amputate the area where the bone would not come together. Dr. Baker's research led to electrical devices being able to signal to the bones to begin to regrow together.