Fig. 7. Neurodegeneration in npc2a; npc2b double mutant Drosophila. (A) Survival data for flies of different genotypes. All mutant designations refer to homozygous animals. KG05307 indicates the starting strain for generating npc2a mutants. The x-axis indicates the time in days and the y-axis shows the percentage of flies surviving. (B) Evidence for apoptotic cell death in the nervous system of mutant flies. Wild-type brains (upper left) had little or no TUNEL staining, so there was little normal cell death. A small number of cells were stained by TUNEL in npc2a mutants (upper right, arrow). Lower left and, magnified, lower right: npc2a; npc2b double mutants had far more frequent death of neurons (arrow) and tracheal cells (arrowhead). (C) The apoptotic cells (labeled by TUNEL) in npc2a; npc2b double mutants included neurons (labeled by anti-Elav, arrow in the merged panel) and non-neurons (arrowhead in the merged panel). (D) Synaptotagmin staining of wild-type and npc2a axon bundles. The accumulation of Synaptotagmin (arrow) within axon tracts was observed in a small number of axons in npc2a mutants but not wild type.