Atg13 homozygous third instar larval mushroom bodies show prevalent disintegration of the core into multiple bundles and defects in the extension of calix dendrites, as compared to controls.
Atg13 homozygous clones within mosaic third instar larval mushroom bodies show prevalent peduncle defects (split fascicles are observed in nearly half of cases) and defects in the extension of calix dendrites, although both the dorsal and the medial lobes do not show defects, as compared to control clones. The majority of Atg13 homozygous lateral neuroblast clones lead to antennal lobe projection neurons fasciculation defects, although most of the anterodorsal neuroblast clones do not lead to obvious defects in axonal projections, as compared to control clones. Projection neurons clones show mild to severe ectopic innervation of the off-target glomeruli DA1, DM5 and DM2 glomeruli, but do not affect the VA2, VA1d, VA1lm, VA3, VM2, DM6, DL1 or VM7 glomeruli, as compared to controls.
Atg13 homozygous DL1 clones lead to a small but significant increase in the number of branches in the calyx, but not in the number of terminal branches in the lateral horn, as compared to clones; a significant proportion of Atg13 homozygous adult antennal lobe projection neuron clones (anterodorsal neuroblast clones, lateral neuroblast clones or ventral neuroblast clones) exhibit overextending dendrites, overshooting as compared to controls.
Atg13 heterozygous neuromuscular junctions exhibit wild-type bouton levels.
Marker analysis indicates that pre-and post synaptic component of the neuromuscular junction fail to align properly in Atg13 homozygous or Atg125/Atg13 heterozygous larvae. In addition, in Atg13 homozygotes the size of neuromuscular junctions (NMJs) is reduced, as is the density of puncta within these junctions. This reduction in size appears not to be due to retraction of an initially normal sized NMJ, as there is not sign of junctional proteins on the muscle surface outside of the NMJ. Ultrastructural analysis reveals that, while many aspects ultrastructure of boutons in these mutants, they have lower densities of active zones, t-bars and active zones containing t-bars. These structural defects in NMJs are accompanied by an approximately 3 fold decrease in the amplitude of evoked excitatory junction potentials (EJPs). There is no accompanying change in spontaneous mini excitatory junction potential (mEJP) amplitude. Atg13/Atg1EY07351 NMJs show the same electrophysiological defects and also exhibit a significant decrease in mEJP frequency.
Accumulation of synaptic material is seen in the axons of motor neurons in Atg13 homozygous larvae.