Fig. 4. Point mutations in the AP-2 binding domain of arrestin do not cause rapid light-dependent degeneration. All panels are cross sections (0.5 µm) of Drosophila retinas from (A) wild-type, (B) arr2^null, (C) arr2^K391A and (D) arr2^R393A flies. Dark reared flies were treated with 5 days of constant room light then fixed and sectioned as described in Materials and Methods.