ABS 026: Characterizing development neurotoxicity in a Drosophila melanogaster model of Huntington’s disease

Meredith Jenkins ¹ , Morgan G. Thomas, Ph.D. ¹ , Bess Frost, Ph.D. ¹

¹ Center for Alzheimer’s Disease Research, Robert J. & Nancy D. Carney Institute for Brain Science, Department of Molecular Biology, Cell Biology, and Biochemistry, Brown University

The Van Wickle Journal (2026) Volume 2, ABS026

Introduction: Huntington’s disease (HD) is a genetic neurodegenerative disorder caused by an expanded polyglutamine (polyQ) repeat in the gene that encodes for the huntingtin protein (HTT), which leads to the formation of toxic, insoluble aggregates of mutant HTT. Though aggregation is a hallmark of HD pathology, the cellular factors that regulate this neurotoxic pathology remain incompletely understood. Developmental factors are of particular interest, as HTT has been implicated in a variety of key neurodevelopmental processes, including chromatin regulation and neural migration. To expand upon current research in the field, we investigated developmental influences of mutant HTT in a Drosophila melanogaster model of HD (GMR-HTT). We identified a temperature-dependent, necrotic eye phenotype featuring dispersed black ommatidia and peeling of the corneal lens in a subset of GMR-HTT flies raised in alternating 17 and 25℃ temperatures. The selective emergence of this phenotype indicates developmental modulation of the neurotoxic effects of mutant HTT, which may be achieved through temperature-sensitive proteins. Current work aims to vary temperature conditions across developmental stages to reliably produce and characterize this phenotype, as well as to analyze corresponding HTT expression levels through RNA sequencing. Results will provide insight concerning the manner in which toxic forms of HTT interact with temperature-dependent factors in the context of development, revealing early formative pathways that contribute to HD neurotoxicity in Drosophila.

Methods: This study utilizes GMR-HTT, a Drosophila model that features a glass multimer reporter (GMR) fusion construct that encodes a 17-amino-acid fragment of human HTT exon 1, followed by 120 polyQ repeats and 125 additional amino acids of HTT. As a result, transgene expression is driven exclusively in the eye. To generate the necrotic eye phenotype, bottles containing GMR-HTT stocks (from which adults had been removed) were placed in a 25°C incubator for 8 hours and then switched to a 17°C incubator for 16 hours in a repetitive cycle. A grape juice plate developmental assay and a time-controlled mating process were used to isolate periods of vulnerability to HTT-induced neurotoxicity across developmental stages. Western blotting was utilized for protein-level assessment, and computational analysis was performed using the R programming language.

Results: In the GMR-HTT system, we identified a putative temperature-dependent phenotypic marker of HD-induced neurotoxicity, as well as a unique HTT protein species via Western blot that is selectively present in Drosophila with the necrotic eye phenotype. Analysis of NE production also indicated periodicity in phenotype frequency that is well-described by a Fourier series model.

Discussion: Future studies may use immunoprecipitation and mass spectrometry to further characterize the 171 kDa HTT protein generated in Drosophila harboring a necrotic eye. Investigating the periodic nature of necrotic eye production may also reveal critical periods of environmental impact in modulating HD-induced neurotoxicity.

As an established genetic disorder, the potential for environmental manipulation during development to induce a unique manifestation of toxicity in HD has a variety of implications regarding human treatment. This study has, overall, begun to elucidate developmental factors contributing to huntingtin neurotoxicity, as well as provided new avenues of inquiry concerning interactions between huntingtin and temperature-sensitive proteins.