Proteins containing an expanded polyglutamine tract are neurotoxins. The expanded polyglutamine proteins influence a variety of cellular functions. In Drosophila the GMR-Gal4/UAS expression system has been widely used...Proteins containing an expanded polyglutamine tract are neurotoxins. The expanded polyglutamine proteins influence a variety of cellular functions. In Drosophila the GMR-Gal4/UAS expression system has been widely used in an eye-based model to study human neurodegenerative diseases. This system has facilitated the isolation and characterization of abundant Drosophilagenes that interact with the expanded polyglutamine proteins. We used the GMR-Gal4/UAS system to express three proteins containing an expanded polyglutamine tract, or an expanded polyglutamine tract alone. Doubling the dose of these proteins resulted in pupal lethality, indicating that these toxic proteins induced a sensitized condition that is prone to synthetic lethality. By using the GMR-Gal4/UAS system, we showed that a Drosophilagene interacts with three expanded polyglutamine proteins to induce a synthetic lethal phenotype. We further demonstrated that the synthetic lethality was mediated through the toxic expanded polyglutamine tract. Our study raises a possibility that conventional genetic screens may not recover synthetic lethal alleles, which are presumably stronger interacting alleles than the currently known modifiers of an expanded polyglutamine tract, due to synthetic lethality.展开更多
Mutant proteins containing an expanded polyglutamine tract induce cell death and cause neurodegenerative diseases. These toxic proteins interfere with a variety of physiological pathways, but the key interactions betw...Mutant proteins containing an expanded polyglutamine tract induce cell death and cause neurodegenerative diseases. These toxic proteins interfere with a variety of physiological pathways, but the key interactions between the toxins and cellular factors remain unclear. To model the diseases in Drosophila, the GMR-Gal4/UAS gene expression system has been used extensively, which operates in the eyes. By using the system, genome-wide studies have resulted in the isolation of functionally diverse groups of Drosophila genes that interact with the disease proteins. We previously reported that coexpressing the Drosophila Dikar gene and an expanded polyglutamine tract by GMR-Gal4/UAS induced a synthetic lethality. We carried out follow-up experiments to isolate additional synthetic lethal alleles. Our data provide evidence that synthetic lethality associated with expressing an expanded polyglutamine tract is more common than thought to be and could have escaped the conventional genetic screens. Our results also suggest that 1) the gene expression system is leaky, allowing expression outside of the primary target eye cell types;2) expressing an expanded polyglutamine tract is extremely toxic to cells;and 3) combining the leaky expression and the toxicity results in a lethal-prone condition. Thus, genetic modifications to the disease proteins’ acute toxicity could frequently lead to synthetic lethality. However, synthetic lethal alleles are excluded from most conventional screens, necessitating alternative approaches such as a two-step method used in this study to isolate the modifiers. Since synthetic lethality reflects essential genetic buffering networks, studying these alleles may hold the keys to identify the critical interactions in the disease development between the toxic proteins and the physiological pathways.展开更多
文摘Proteins containing an expanded polyglutamine tract are neurotoxins. The expanded polyglutamine proteins influence a variety of cellular functions. In Drosophila the GMR-Gal4/UAS expression system has been widely used in an eye-based model to study human neurodegenerative diseases. This system has facilitated the isolation and characterization of abundant Drosophilagenes that interact with the expanded polyglutamine proteins. We used the GMR-Gal4/UAS system to express three proteins containing an expanded polyglutamine tract, or an expanded polyglutamine tract alone. Doubling the dose of these proteins resulted in pupal lethality, indicating that these toxic proteins induced a sensitized condition that is prone to synthetic lethality. By using the GMR-Gal4/UAS system, we showed that a Drosophilagene interacts with three expanded polyglutamine proteins to induce a synthetic lethal phenotype. We further demonstrated that the synthetic lethality was mediated through the toxic expanded polyglutamine tract. Our study raises a possibility that conventional genetic screens may not recover synthetic lethal alleles, which are presumably stronger interacting alleles than the currently known modifiers of an expanded polyglutamine tract, due to synthetic lethality.
文摘Mutant proteins containing an expanded polyglutamine tract induce cell death and cause neurodegenerative diseases. These toxic proteins interfere with a variety of physiological pathways, but the key interactions between the toxins and cellular factors remain unclear. To model the diseases in Drosophila, the GMR-Gal4/UAS gene expression system has been used extensively, which operates in the eyes. By using the system, genome-wide studies have resulted in the isolation of functionally diverse groups of Drosophila genes that interact with the disease proteins. We previously reported that coexpressing the Drosophila Dikar gene and an expanded polyglutamine tract by GMR-Gal4/UAS induced a synthetic lethality. We carried out follow-up experiments to isolate additional synthetic lethal alleles. Our data provide evidence that synthetic lethality associated with expressing an expanded polyglutamine tract is more common than thought to be and could have escaped the conventional genetic screens. Our results also suggest that 1) the gene expression system is leaky, allowing expression outside of the primary target eye cell types;2) expressing an expanded polyglutamine tract is extremely toxic to cells;and 3) combining the leaky expression and the toxicity results in a lethal-prone condition. Thus, genetic modifications to the disease proteins’ acute toxicity could frequently lead to synthetic lethality. However, synthetic lethal alleles are excluded from most conventional screens, necessitating alternative approaches such as a two-step method used in this study to isolate the modifiers. Since synthetic lethality reflects essential genetic buffering networks, studying these alleles may hold the keys to identify the critical interactions in the disease development between the toxic proteins and the physiological pathways.