As the mutant flies age, they develop domains of reduced tissue density and integrity in the MB that manifest as a vacuolar pathology in histological sections, and they display gross swelling of the proximal axon in a significant fraction of MB projection neurons.
Young atg7 generic null mutant flies mimicked aged flies in showing both this increase in BRP staining, as well as an inability to form olfactory memories37,39.
Two independent samples of 25 female flies were used for each condition (young virgin flies, young mated flies, aged virgin flies and aged mated flies).
As flies aged, we began to detect fragmentation of the axons and dendrites of MB projection neurons both in wild-type and p35 mutant neurons using MARCM mosaics (Fig. 5).
A decline in locomotion was observed in both unmated mutant and unmated control females, however, a continued higher level of mobility in older mutant flies indicated slowed aging.
Indeed, these aged mutant flies have stronger circadian behavioral rhythms compared to sibling controls under constant darkness conditions (Fig. 6A, Table 2).
Briefly, brains of wild-type or p35 mutant flies of different ages were explanted and cultured briefly in propidium iodide (PI), and the fraction of necrotic cells in the MB cortex was quantified based on loss of PI exclusion and nuclear engorgement (see Methods for details) (Fig. 3A,B).
Thus, histological analysis of the brains of aging p35 mutant flies presented evidence of general degeneration throughout the central brain and selective, age-dependent tissue disruption in a specific structure, the MB.
We now show that aging p35 mutant flies suffer adult-onset neurodegeneration, with overt tissue disruption in a specific structure of the central brain, the 'mushroom bodies' (MB), which are the seat of olfactory learning and memory.
This was also true for lamG262 flies, but the fraction of mutants that climbed was lower than age matched controls, and the decrease was much more dramatic for mutant flies, approaching zero at two weeks of age.
