A construct system for expressing a reporter protein, as well as a transgenic animal and a screening method employing the same, are provided. In certain embodiments, the construct system is a three component system in which expression of a reporter protein from a reporter construct is induced by a transcription factor that is produced using two other constructs, each producing a different part of the transcription factor. The parts of the transcription factor are ligated together. Expression of the reporter only occurs in tissues in which both of the parts of the transcription factor are produced.
