Early in embryonic development, atonal is expressed in all chordotonal organ progenitor cells, but its later expression is restricted to only a particular set of precursors, through a process of lateral inhibition. Notch does not seem to be required for this process in chordotonal organs, and the mechanism is not well understood.
Atonal protein is produced in all cells just anterior to the morphogenic furrow.
Expression is downstream of hedgehog , an important gene involved in regulating the progression of the furrow. As the furrow progresses, most cells that express atonal in front of the furrow lose that capacity. The function of Atonal is best illustrated by its role in chordotonal organ development. Expression of atonal is restricted to a subset of atonal -requiring chordotonal precursors, called founder precursors. This one scolopidium formed in atonal mutants is atonal independent.