An automated climbing apparatus to measure chemotherapy-induced neurotoxicity in Drosophila melanogaster

Abstract

We have developed a novel model system in Drosophila melanogaster to study chemotherapy-induced neurotoxicity in adult flies. Neurological deficits were measured using a manual geotactic climbing assay. The manual assay is commonly used; however, it is laborious, time-consuming, subject to human error and limited to observing one sample at a time. We have designed and built a new automated fly-counting apparatus that uses a "video capture-particle counting technology" to automatically measure 10 samples at a time, with 20 flies per sample. Climbing behavior was assessed manually, as in our previous studies, and with the automated apparatus within the same experiment yielding statistically similar results. Both climbing endpoints as well as the climbing rate can be measured in the apparatus, giving the assay more versatility than the manual assay. Automation of our climbing assay reduces variability, increases productivity and enables high throughput drug screens for neurotoxicity.

Keywords: Drosophila; apparatus; automated; chemotherapy; cisplatin; climbing; geotactic; neurotoxicity.

Figure 1. Schematic drawing of the fly-counting apparatus.

Figure 2. The fly-counting apparatus is consists of (A) the computer and plexiglass enclosure. Within (B) the enclosure is the (c) camera, the tapping assembly consisting of the (t) tapping mechanism, (v) vial holder and (l) LED lights. Closer examination of the (C) vial holder, (D) lights, (E) tapping mechanism and (F) camera shows the components of the apparatus in more detail. The camera acquires a (G) digital image, which is imported into Image J software and analyzed by (H) particle counting, which is then (I) displayed on the computer screen.

Figure 3. Side-by-side analysis of the geotaxis climbing assay between the fly-counting apparatus and the manual assay was found to be comparable. (A) Percent survival and percent of flies able to climb above 2 cm was performed in the apparatus followed by the manual assay on the same flies. (B) There was no statistical difference in climbing ability of the flies between the apparatus and the manual assay (p > 0.005). Variability within each assay was also similar. (C) Prickle flies were tested for climbing ability in both the manual assay and the apparatus with no statistical difference between the two. (p > 0.05) (D) Climbing ability in prickle flies was assessed in the apparatus with the climbing height (threshold) set at 0.5, 1 and 2 cm. Although we were able measure more flies climbing above 1 cm than 2 cm there was no statistical difference between the two. (p > 0.05) .

Figure 4. Climbing ability in the fly-counting apparatus can be measure as both a maximum height able to climb as well as the rate of climbing. (A) Cisplatin treated flies were assessed for the percent of flies able to climb above 4 cm at 2, 4, 6, 8 and 10 sec. (B) We were able to determine the maximum percent of flies able to climb above 4 cm as well as the rate of climbing expressed as the percent of flies able to climb above 4 cm per second. There was a significant decrease in maximum climbing and rate of climbing at 25, 50 and 100 ug/ml cisplatin (p < 0.005). No significant difference observed at 10 ug/ml cisplatin.