Table 1. Summary of cho mutants used.

Gene	Symbol	cho class	Ref.
atonal	ato	Specification	21, 25, 37
beethoven	btv	Ciliary	19, 25
touch-insensitive larva B	tilB	Axonemal	20, 25
smetana	smet	Axonemal	38
5D10	5D10	Courtship defective	19, 38

ato encodes a proneural bHLH protein that specifies cho precursor cells. In ato mutants, chos are absent in both adults and larvae. btv is a cho mutant that exhibits ultrastructural defects in the cho cilium, whereas smet and tilB mutants show male sterility in addition to deafness, suggesting specific defects of the axoneme. Finally, 5D10 mutants, found in a courtship defective auditory behavioral screen, show moderate cho dysfunction.