Fig. 4

α-synuclein-induced retinal degeneration and screening assays in Drosophila transgenic animals. Tangential sections through the fly retina stained with hematoxylin and eosin reveal the ordered ommatidial array in control animals (a Rh1-GAL4 / +). Each ommatidia consists of a cluster of eight photoreceptive neurons (seven visible at the level examined). The photoreceptors each contain a single rhabdomere, the specialized organelle subserving phototransduction, giving the ommatidia cluster its characteristic appearance (arrowhead). Expression of α-synuclein in adult photoreceptors (b, c Rh1-GAL4 / +; UAS-α-synuclein / +) causes age-dependent, progressive retinal degeneration. Compared to one-day-old Rh1 > α-synuclein flies (b), histologic sections in 30-day-old animals (c) demonstrate rhabdomere/cell loss and substantial vacuolar changes (asterisk). The pseudopupil preparation allows visualization of rhabdomeres (arrowhead) in intact, unfixed intact fly heads, permitting medium-throughput screening for progression of α-synuclein-induced retinal pathology. Compared to controls (d Rh1-GAL4 / +), in 30-day-old α-synuclein transgenic animals (e Rh1-GAL4 / +; UAS-α-synuclein / +) rhabodomeres frequently appear indistinct (arrowhead) and vacuolar changes disrupt light refraction (asterisk). Representative control histology (a) and pseudopupil images (d) are shown for 15-day-old animals, the timepoint used for screening, in order to facilitate comparison with Fig. 5. Scale bar: 20 μm