Tan, K. J. | Search bioRxiv

bioRxiv2025

Novel regional specific voltage-gated sodium channel (vgsc) mutations underlying pyrethroid resistance in Aedes albopictus (Skuse) from Northern Peninsular Malaysia

BackgroundControlling Aedes mosquitoes remains as a primary means through the application of synthetic insecticides in Malaysia, but its efficacy is undermined by the evolution of resistance. Aedes albopictus as one of the dominant and competent arboviral vectors has an elusive insecticide resistance status in different geographical regions of Northern Peninsular Malaysia. This underscores the importance of assessing the diverse types of insecticides used and their association with target-site resistance mechanism in this species, which forms the basis of the present study. MethodsWHO-bioassays were performed on Ae. albopictus larvae and adults from four localities (Penang and Perlis), towards 0.034 ppm temephos, 0.25% permethrin, 0.03% deltamethrin, 0.25% primiphos methyl and 0.1% propoxur. The partial voltage-gated sodium channel (vgsc) gene domain (DIIS6, DIIIS6, and DIVS6) of pyrethroid-exposed samples were subsequently genotyped through direct sequencing for any diagnostic single-nucleotide mutations, together with genetic variations and haplotype networks analysis. The predicted protein structures for the mutated regions and their binding affinities to pyrethroids were also evaluated using in-silico docking. Results and discussionsVarying degrees of resistance were observed in all Penang and Perlis strains to all tested insecticides. Moreover, the detection of the F1534L mutation and newly discovered non-synonymous mutations (A1022S/P, E1041K, P1585R, and F1695L) suggest the progression of resistance alleles dissemination in other strains. The analysis of genetic variations, resistance allele distribution patterns, and haplotype networks showed evidence for multiple origins of these mutations. Data also revealed the discovered mutations affect the affinity of vgsc-binding proteins to pyrethroids. ConclusionThis study highlights the genotype-phenotype associations in Ae. albopictus and their genetic links to pyrethroid resistance, offering insights to strengthen vector control strategies in Malaysia. Author summaryIn Malaysia, as in many other countries, dengue epidemic control primarily relies on managing the main vector, Ae. albopictus through commercially available insecticide applications. Vector control strategies have been extensively implemented by local health authorities, often without comprehensive information on insecticide resistance mechanisms in vector populations that could pose a major drawback of insecticide used. In an effort to assess the susceptibility status of Ae. albopictus populations, and determine the most effective insecticide for reducing Malaysian vector populations from different geographical settings, we conducted bioassays towards pyrethroid, organophosphate, and carbamate insecticide classes. Altogether, molecular-based assays were incorporated with phenotypic assay to elucidate the mechanisms modulating insecticide resistance and to unravel their genetic dynamics. Such screening offers detailed insights into specific mechanisms involved in conferring resistance for distinct adopted insecticides. This evidence aims to guide local health authorities in developing vector control strategies and exploring alternative solutions.

evolutionary biology↗

bioRxiv2018

Automated leg tracking reveals distinct conserved gait and tremor signatures in Drosophila models of Parkinson’s Disease and Spinocerebellar ataxia 3

Genetic models in Drosophila have made invaluable contributions to our understanding of the molecular mechanisms underlying neurodegeneration. In human patients, some neurodegenerative diseases lead to characteristic movement dysfunctions, such as abnormal gait and tremors. However, it is currently unknown whether similar movement defects occur in the respective fly models, which could be used to model and better understand the pathophysiology of movement disorders. To address this question, we developed a machine-learning image-analysis programme -- Feature Learning-based LImb segmentation and Tracking (FLLIT) -- that automatically tracks leg claw positions of freely moving flies recorded on high-speed video, generating a series of body and leg movement parameters. Of note, FLLIT requires no user input for learning. We used FLLIT to characterise fly models of Parkinsons Disease (PD) and Spinocerebellar ataxia 3 (SCA3). Between these models, walking gait and tremor characteristics differed markedly, and recapitulated signatures of the respective human diseases. Selective expression of mutant SCA3 in dopaminergic neurons led to phenotypes resembling that of PD flies, suggesting that the behavioural phenotype may depend on the circuits affected, rather than the specific nature of the mutation. Different mutations produced tremors in distinct leg pairs, indicating that different motor circuits are affected. Almost 190,000 video frames were tracked in this study, allowing, for the first time, high-throughput analysis of gait and tremor features in Drosophila mutants. As an efficient assay of mutant gait and tremor features in an important model system, FLLIT will enable the analysis of the neurogenetic mechanisms that underlie movement disorders.

neuroscience↗