A simple helix-loop-helix transcription factor isTranscription Factor 4 (TCF4). An Ephrussi-box (‘E-box’)binding site (‘CANNTG’), initially discovered inimmunoglobulin enhancers, is recognised by the encodedprotein. This gene is widely expressed and could be crucialfor the development of the nervous system. Pitt-Hopkinssyndrome is brought on by abnormalities in this gene.