A cost effective high-resolution climbing assay applied to Drosophila Parkinson’s and proprioception mutants reveal novel behavioural phenotypes

Abstract

Severe locomotor impairment is a common phenotype of neurodegenerative disorders such as Parkinson's disease (PD). Drosophila models of PD, studied from more than a decade, have helped in understanding the interaction between various genetic factors, such as parkin and PINK1, in this disease. To characterize locomotor behavioural phenotypes for these genes, fly climbing assays have been widely used. While these simple current assays for locomotor defects in Drosophila mutants measure some locomotor phenotypes well, it is possible that detection of subtle changes in behaviour is important to understand the early manifestation of locomotor disorders. We introduce a novel climbing behaviour assay which provides such fine-scale behavioural data and tests this proposition for the Drosophila model. We use this inexpensive, fully automated, high resolution assay to quantitatively characterize the parameters of climbing behaviour in three contexts. First, we characterize wild type flies and uncover a hitherto unknown sexual dimorphism in climbing behaviour. Second, we study climbing behaviour of heterozygous mutants of genes implicated in the fly PD model and reveal previously unreported prominent locomotor defects in some of these heterozygous fly lines. Finally, we study locomotor defects in a homozygous proprioceptory mutation (Trp-γ 1 ) known to affect fine motor control in Drosophila.Moreover, we identify aberrant geotactic behaviour in Trp-γ 1 mutants, thereby opening up a finer assay for geotaxis and its genetic basis. Our assay is therefore a cost-effective, general tool for measuring locomotor behaviours of wild type and mutant flies in fine detail and can reveal mild motor defects.Fine control of neuronal activity is required for proper motor output. Severe locomotor impairment is a common result of neurodegenerative disorders such as Parkinson's disease (PD). The fruitfly, Drosophila, has been widely used as a model system to study the genetics of these disorders and simple climbing assays have been used to study the behavioural phenotypes of mutations in these genes. Here we introduce a novel, fully automated, high resolution climbing behaviour assay and use this assay to characterize climbing behaviour in wild type flies and in various fly mutant lines related to PD and defects in proprioception. Our assay is a general tool for measuring locomotor behaviours of flies in fine detail and can reveal very mild motor defects.

Fully automated leg tracking of Drosophila neurodegeneration models reveals distinct conserved movement signatures

“…Using FLLIT, we characterized, for the first time, specific gait and tremor dysfunctions in fly neurodegeneration mutants. These mutants would be undifferentiable using classic climbing or locomotor assays, although it would be interesting to test them in a recently reported sensitive climbing assay [49]. Gait characterization allows comparison to human movement disorders, for which gait parameters measured in the clinic can be used to aid disease diagnosis.…”

Identification and functional characterization of two novel mutations in KCNJ10 and PI4KB in SeSAME syndrome without electrolyte imbalance

“…The videos were captured at 15FPS at 0.064mm/pixel resolution. Live imaging done using FlyCon Tra (Fly Contour based Tracker) software (Aggarwal et al, 2018). Statistical analysis of all raw data gathered over time for both fly bowl and vertical climbing assay was done using GraphPad Prism (San Diego, USA).…”

“…We used high-resolution live-tracking adult locomotor assays in two independent platforms; a vertical fly-climbing assay to measure fly's innate response to gravity and its role in patterns of locomotion, thereby indirectly assaying the drive to move ( Fig. 6A; Aggarwal et al, 2018) whereas horizontal fly-bowl assay which measures locomotion in a cue free environment (Fig. 6D; Simon and Dickinson, 2010).…”

“…6D; Simon and Dickinson, 2010). In the vertical fly-climbing assay, 5day old flies were provided with regular stimulus for locomotion by rotating the arena for fly climbing every 15 seconds (Aggarwal et al, 2018). The innate geotactic response of the flies makes them always climb towards the top of the arena, and when, after 15 seconds, the arena is rotated 180 degrees, the flies which are on the top are now pushed downwards providing them with the geotactic stimulus.…”