Comparison of neuronal GAL4 drivers along with the AGES (auxin-inducible gene expression system) and TARGET (temporal and regional gene expression targeting) systems for fine tuning of neuronal gene expression in Drosophila

The astrocyte-enriched gene deathstar plays a crucial role in the development, locomotion, and lifespan of D. melanogaster

The Drosophila melanogaster brain is a complex organ with various cell types, orchestrating the development, physiology, and behaviors of the fly. While each cell type in Drosophila brain is known to express a unique gene set, their complete genetic profile is still unknown. Advances in the RNA sequencing techniques at single-cell resolution facilitate identifying novel cell type markers and/or re-examining the specificity of the available ones. In this study, exploiting a single-cell RNA sequencing data of Drosophila optic lobe, we categorized the cells based on their expression pattern for known markers, then the genes with enriched expression in astrocytes were identified. CG11000 was identified as a gene with a comparable expression profile to the Eaat1 gene, an astrocyte marker, in every individual cell inside the Drosophila optic lobe and midbrain, as well as in the entire Drosophila brain throughout its development. Consistent with our bioinformatics data, immunostaining of the brains dissected from transgenic adult flies showed co-expression of CG11000 with Eaat1 in a set of single cells corresponding to the astrocytes in the Drosophila brain. Physiologically, inhibiting CG11000 through RNA interference disrupted the normal development of male D. melanogaster, while having no impact on females. Expression suppression of CG11000 in adult flies led to decreased locomotion activity and also shortened lifespan specifically in astrocytes, indicating the gene's significance in astrocytes. We designated this gene as 'deathstar' due to its crucial role in maintaining the star-like shape of glial cells, astrocytes, throughout their development into adult stage.

A drug stabilizable GAL80ds for conditional control of gene expression via GAL4-UAS and CRISPR-Cas9 systems in Drosophila

The binary GAL4-UAS expression system has been widely used in Drosophila to achieve tissue-specific expression of genes. To further allow for simultaneous spatial and conditional control of gene expression in existing GAL4 expression lines backgrounds, temperature and chemical controllable GAL80 variants have been engineered. Here we add a new drug stabilizable GAL80ds variant, by fusing it to a low-background DHFR-22-DD. We first quantify both single (DD-GAL80) and double (DD-GAL80-DD) architectures and show varied background and activation levels. Next, we demonstrate the utility of GAL80ds Drosophila line to regulate a cell death gene ectopically, in a drug-dependent manner, by utilizing an existing tissue-specific GAL4 driver that regulates the expression of a cell death gene under a UAS. Finally, we showcase the usefulness of GAL80ds in tight drug-mediated regulation of a target gene, from an endogenous locus, by utilizing an existing tissue-specific GAL4 to drive the expression of a dead Cas9 variant fused to the transcriptional coactivator nejire, under a UAS and in gRNA lines. Overall, these new GAL80ds lines expand the use of the wide variety of existing tissue-specific GAL4 and gene-specific gRNA lines. This enables conditional control of genes, both ectopically and endogenously, for a broad array of gene expression control applications.

Auxin exposure disrupts feeding behavior and fatty acid metabolism in adult Drosophila

The ease of genetic manipulation in Drosophila melanogaster using the Gal4/UAS system has been beneficial in addressing key biological questions. Current modifications of this methodology to temporally induce transgene expression require temperature changes or exposure to exogenous compounds, both of which have been shown to have detrimental effects on physiological processes. The recently described auxin-inducible gene expression system (AGES) utilizes the plant hormone auxin to induce transgene expression and is proposed to be the least toxic compound for genetic manipulation, with no obvious effects on Drosophila development and survival in one wild-type strain. Here, we show that auxin delays larval development in another widely used fly strain, and that short- and long-term auxin exposure in adult Drosophila induces observable changes in physiology and feeding behavior. We further reveal a dosage response to adult survival upon auxin exposure, and that the recommended auxin concentration for AGES alters feeding activity. Furthermore, auxin-fed male and female flies exhibit a significant decrease in triglyceride levels and display altered transcription of fatty acid metabolism genes. Although fatty acid metabolism is disrupted, auxin does not significantly impact adult female fecundity or progeny survival, suggesting AGES may be an ideal methodology for studying limited biological processes. These results emphasize that experiments using temporal binary systems must be carefully designed and controlled to avoid confounding effects and misinterpretation of results.