Development of the Auditory Organ (Johnston's Organ) in Drosophila

The Drosophila ear, Johnston’s organ (JO), is housed in its antenna. At the heart of JO are intrinsically mechanosensitive ciliated sensory neurons called chordotonal neurons. Development of JO requires formation and patterning of the antennal primordium in the larva, the specification of the precursor cells of the mechanosensory units, the differentiation of the chordotonal neurons, and the targeting of their axons to the antennal mechanosensory and motor centre (AMMC) of the brain. JO chordotonal neurons combine the functions of vertebrate hair cells and auditory neurons. Although they differ in structure, clear developmental, genetic and physiological parallels between the Drosophila and vertebrate auditory systems suggest that chordotonal neurons and hair cells are orthologous cell types and that the auditory systems evolved from the same ancestral mechanoreceptive organ.