Wu S, Tan KJ, Govindarajan LN, Stewart JC, Gu L, Ho JWH, et al. (2019) Fully automated leg tracking of Drosophila neurodegeneration models reveals distinct conserved movement signatures. PLoS Biol 17(6): e3000346. https://doi.org/10.1371/journal.pbio.3000346
Some neurodegenerative diseases, like Parkinsons Disease (PD) and Spinocerebellar ataxia 3 (SCA3), are associated with distinct, altered gait and tremor movements that are reflective of the underlying disease etiology. Drosophila melanogaster models of neurodegeneration have illuminated our understanding of the molecular mechanisms of disease. However, it is unknown whether specific gait and tremor dysfunctions also occur in fly disease mutants. To answer this question, we developed a machine-learning image-analysis program, Feature Learning-based LImb segmentation and Tracking (FLLIT), that automatically tracks leg claw positions of freely moving flies recorded on high-speed video, producing a series of gait measurements. Notably, unlike other machine-learning methods, FLLIT generates its own training sets and does not require user-annotated images for learning. Using FLLIT, we carried out high-throughput and high-resolution analysis of gait and tremor features in Drosophila neurodegeneration mutants for the first time. We found that fly models of PD and SCA3 exhibited markedly different walking gait and tremor signatures, which recapitulated characteristics of the respective human diseases. Selective expression of mutant SCA3 in dopaminergic neurons led to a gait signature that more closely resembled those of PD flies. This suggests that the behavioral phenotype depends on the neurons affected rather than the specific nature of the mutation. Different mutations produced tremors in distinct leg pairs, indicating that different motor circuits were affected. Using this approach, fly models can be used to dissect the neurogenetic mechanisms that underlie movement disorders.
This work was supported by the Institute of Molecular and Cell Biology, Singapore; the Bioinformatics Institute, Singapore; the Agency for Science Technology and Research Joint Council Organization (grant number 15302FG149 to SA, LC, ACC and EKT and grant number 1431AFG120 to LC and ACC); and the Clinical Research Flagship Programme (Parkinson’s Disease) administered by the Singapore Ministry of Health’s National Medical Research Council (grant number NMRC/TCR/013-NNI/2014 to SA and EKT), and Star Investigator Award (EKT).