AR and retinal degeneration: We began by utilizing Drosophila. When a full-length AR transgene is expressed in the Drosophila eye via the Gal4/UAS system (Brand and Perrimon, 1993), it produces a polyQ-, DHT-dependent retinal degeneration phenotype characterized by the presence of fused ommatidia and abnormal interommatidial bristles along the posterior margin of the eye (Figure 3A,B and Figure 3—figure supplement 1).