P.090 Evaluation of Mutant Alleles of Engrailed and Invected in Drosophila Melanogaster Models of Parkinson Disease

Background: Parkinson Disease (PD) is a neurodegenerative disorder, resulting in a gradual decline in voluntary movement, where lifespan remains stable. Drosophila melanogaster offer comparable gene sequences to those targeted in PD; among them are two transcription factors, engrailed (en) and invected (inv). Methods: Wild-type homozygous allele Oregon-R(en+, inv+) was compared to heterozygous mutants of en1, en4, en7, en54, en58, invW, inv30, and Df (2R) enEinvE. Nine climbing and aging studies were executed from crosses with w1118(en+, inv+) as the maternal genotype. Results: Independent-samples t-tests were conducted to compare the percent survival (in days). No significant differences were observed between the experimental groups and the control group. A mixed Analysis of Variance was conducted to compare climbing behaviour over time (in weeks) for all nine groups. Both main effects (group, time), and the interaction (group x time) were significant. Post hoc Fisher’s Least Significant Difference tests revealed a significant difference between the control group and en1, en4, en54, invW, and Df (2R) enEinvE groups. Conclusions: These results support the hypothesis that mutations of en, inv, or both will result in a PD phenotype and consequent decreased motor function of D. melanogaster PD models, with or without a significant decrease in lifespan.

High-resolution analysis of baculovirus-induced host manipulation in the domestic silkworm, Bombyx mori

Many parasites manipulate host behaviour to enhance their transmission. Baculoviruses induce enhanced locomotory activity (ELA) combined with subsequent climbing behaviour in lepidopteran larvae, which facilitates viral dispersal. However, the mechanisms underlying host manipulation system are largely unknown. Previously, larval locomotion during ELA was summarized as the distance travelled for a few minutes at several time points, which are unlikely to characterize ELA precisely, as ELA typically persists for several hours. In this study, we modified a recently developed method using time-lapse recording to characterize locomotion of Bombyx mori larvae infected with B. mori nucleopolyhedrovirus (BmNPV) for 24 h at 3 s resolution. Our data showed that the locomotion of the mock-infected larvae was restricted to a small area, whereas the BmNPV-infected larvae exhibited a large locomotory area. These results indicate that BmNPV dysregulates the locomotory pattern of host larvae. Furthermore, both the mock- and BmNPV-infected larvae showed periodic cycles of movement and stationary behaviour with a similar frequency, suggesting the physiological mechanisms that induce locomotion are unaffected by BmNPV infection. In contrast, the BmNPV-infected larvae exhibited fast and long-lasting locomotion compared with mock-infected larvae, which indicates that locomotory speed and duration are manipulated by BmNPV.

Reprogramming of larval locomotory pattern during baculovirus-induced host manipulation

Many parasites manipulate host behaviour to enhance their transmission. Baculovirus induces enhanced locomotory activity (ELA) combined with subsequent climbing behaviour in lepidopteran larvae, which facilitates viral dispersal. Previously, larval locomotion during ELA was summarized as the distance travelled for a few minutes at several time points. However, as ELA continues for several hours, these methods are unlikely to evaluate larval locomotion precisely during ELA. We developed a novel method to continuously trace the locomotion of Bombyx mori larvae using time-lapse imaging. This method successfully quantified the locomotory activities of larvae infected with Bombyx mori nucleopolyhedrovirus (BmNPV) for 24 h. We found that both mock- and BmNPV-infected larvae periodically repeated moving and pausing with a similar frequency. In contrast, BmNPV-infected larvae showed fast and long-lasting locomotion compared with mock-infected larvae, which resulted in longer locomotory distances in infected larvae. Moreover, BmNPV-infected larvae exhibited biphasic behaviour. Initially, BmNPV-infected larvae showed longer locomotory distances, but the locomotory pattern was similar to mock-infected larvae. However, during the second phase, the locomotory pattern was drastically altered, with an extremely larger locomotory area. These results indicate that BmNPV reprograms host locomotory pattern, which is a turning point for the process of BmNPV-induced host manipulation.

A simple skeletal measurement effectively predicts climbing behaviour in a diverse clade of small mammals

Arboreal locomotion allows access to above-ground resources and might have fostered the diversification of mammals. Nevertheless, simple morphological measurements that consistently correlate with arboreality remain indefinable. As such, the climbing habits of many species of mammals, living and extinct, remain speculative. We collected quantitative data on the climbing tendencies of 20 species of murine rodents, an ecologically and morphologically diverse clade. We leveraged Bayesian phylogenetic mixed models (BPMMs), incorporating intraspecific variation and phylogenetic uncertainty, to determine which, if any, traits (17 skeletal indices) predict climbing frequency. We used ordinal BPMMs to test the ability of the indices to place 48 murine species that lack quantitative climbing data into three qualitative locomotor categories (terrestrial, general and arboreal). Only two indices (both measures of relative digit length) accurately predict locomotor styles, with manus digit length showing the best fit. Manus digit length has low phylogenetic signal, is largely explained by locomotor ecology and might effectively predict locomotion across a multitude of small mammals, including extinct species. Surprisingly, relative tail length, a common proxy for locomotion, was a poor predictor of climbing. In general, detailed, quantitative natural history data, such as those presented here, are needed to enhance our understanding of the evolutionary and ecological success of clades.

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

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-γ1) known to affect fine motor control in Drosophila. Moreover, we identify aberrant geotactic behaviour in Trp-γ1 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.Significance statementFine 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.

Timely trigger of caterpillar zombie behaviour: temporal requirements for light in baculovirus-induced tree-top disease

Host behavioural manipulation is a common strategy used by parasites to enhance their survival and/or transmission. Baculoviruses induce hyperactivity and tree-top disease (pre-death climbing behaviour) in their caterpillar hosts. However, little is known about the underlying mechanisms of this behavioural manipulation. A previous study showed that the baculovirus Spodoptera exigua multiple nucleopolyhedrovirus (SeMNPV) induced tree-top disease at 3 days post infection in third instar S. exigua larvae and that light plays a key role in triggering this behaviour. Here we investigated the temporal requirements for the presence of light to trigger this behaviour and found that light from above was needed between 43 and 50 h post infection to induce tree-top disease. Infected larvae that were not exposed to light from above in this period finally died at low positions. Exposure to light prior to this period did not affect the final positions where larvae died. Overall we conclude that light in a particular time frame is needed to trigger SeMNPV-induced tree-top disease in S. exigua larvae.