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BackgroundOne of the hallmarks of Alzheimer's disease, and several other degenerative disorders such as Inclusion Body Myositis, is the abnormal accumulation of amyloid precursor protein (APP) and its proteolytic amyloid peptides. To better understand the pathological consequences of inappropriate APP expression on developing tissues, we generated transgenic flies that express wild-type human APP in the skeletal muscles, and then performed anatomical, electrophysiological, and behavioral analysis of the adults.ResultsWe observed that neither muscle development nor animal longevity was compromised in these transgenic animals. However, human APP expressing adults developed age-dependent defects in both climbing and flying. We could advance or retard the onset of symptoms by rearing animals in vials with different surface properties, suggesting that human APP expression-mediated behavioral defects are influenced by muscle activity. Muscles from transgenic animals did not display protein aggregates or structural abnormalities at the light or transmission electron microscopic levels. In agreement with genetic studies performed with developing mammalian myoblasts, we observed that co-expression of the ubiquitin E3 ligase Parkin could ameliorate human APP-induced defects.ConclusionsThese data suggest that: 1) ectopic expression of human APP in fruit flies leads to age- and activity-dependent behavioral defects without overt changes to muscle development or structure; 2) environmental influences can greatly alter the phenotypic consequences of human APP toxicity; and 3) genetic modifiers of APP-induced pathology can be identified and analyzed in this model.

The styli, often called the aristae, of the antennae of adult Sepedon fuscipennis Loew (Diptera: Sciomyzidae) are shown to possess mechanosensilla, the number and arrangement of which differ between the sexes. It is suggested that the mechanosensilla provide sensory input to the female regarding the touching, or appositioning, of her styli by the male with his forelegs during copulation. Among the Sciomyzidae, S.fuscipennis males are unique in appositioning the antennae of the female during mating. Large clusters of pollen found on the styli of both sexes suggest that mechanosensilla and chemosensilla also provide sensory information about potential sources of food such as nectar (i.e., carbohydrates).

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