Deletion removing the late promoter but leaving early expression intact.
eye photoreceptor cell & axon (with sim2)
In sim2/simry75 mutant larval brains, more developing lamina neurons remain in the pre-assembling domain than normal and R axons that project to the smaller assembling domain contain much fewer than the normal number of lamina neurons. The mutant brains are comparable to control brains with regard to the number of differentiated ommatidia and the total number of lamina neurons.