Transcription factor that functions as a master developmental regulator controlling midline development of the ventral nerve cord. Required to correctly specify the formation of the central brain complex, which controls walking behavior. Also required for correct patterning of the embryonic genital disk and anal pad anlage. Plays a role in synapse development. Efficient DNA binding requires dimerization with another bHLH protein. Embryonic nerve cord. Berkeley strain has 11 A-A-Q repeats. Mutations result in the loss of the precursor cells that give rise to midline cells of the embryonic central nervous system.