eyeless (ey) is a key regulator of the eye development pathway in Drosophila. 
Ectopic expression of ey can induce the expression of several eye-specification 
genes (eya, so, and dac) and induce eye formation in multiple locations on the 
body. However, ey does not induce eye formation everywhere where it is 
ectopically expressed, suggesting that EY needs to collaborate with additional 
factors for eye induction. We examined ectopic eye induction by EY in the wing 
disc and found that eye induction was spatially restricted to the posterior 
compartment and the anterior-posterior (A/P) compartmental border, suggesting a 
requirement for both HH and DPP signaling. Although EY in the anterior 
compartment induced dpp and dac, these were not sufficient for eye induction. 
Coexpression experiments show that EY needs to collaborate with high level of HH 
and DPP to induce ectopic eye formation. Ectopic eye formation also requires the 
activation of an eye-specific enhancer of the endogenous hh gene.