OP31 Overexpression of cystathionine γ-lyase partly rescues the phenotype of spinocerebellar ataxia type 3 in Drosophila Melanogaster

Abstract

Background Spinocerebellar ataxia type 3 (SCA3) is a polyglutamine (polyQ) disorder caused by a CAG repeat expansion in the ataxin3-gene. The polyQ expansion leads to neuronal dysfunction and cell death. Besides proteotoxic stress, mitochondrial dysfunction, oxidative stress, inflammation, apoptosis and a disturbed calcium homeostasis are thought to contribute to the multifaceted pathogenesis of SCA3. Hydrogen sulfide (H2S) is endogenously produced by cystathionine γ-lyase (CSE), cystathionine β-synthase and 3-mercaptopyruvate sulfurtransferase and has crucial physiological functions in the central nervous system. It has anti-oxidative, anti-inflammatory and anti-apoptotic properties and regulates calcium homeostasis, making it an attractive candidate to intervene in the damaging processes of SCA3. We therefore investigated the protective role of overexpression of endogenous CSE using a Drosophila melanogaster model of SCA3. Methods In human, CSE mRNA and protein expression was investigated by qRT-PCR and immunohistochemistry of the pons of SCA3 (n = 7) and control (n = 7) patients. Drosophila Melanogaster culture and crosses were performed at 25 °C following standard protocols. CSE mRNA overexpression in CSE transgenic flies was confirmed by qRT-PCR. For eye degeneration experiments, fly stocks expressing the mutated human ataxin3 gene with 78 repeats in the presence or absence of overexpression of CSE in eye tissue were used. Isogenic wild type flies were used as controls. To inhibit CSE, the crosses were performed on food containing propargylglycine (1 mM). Twenty-four hours after eclosion, each male eye was scored for degeneration. Per cross, at least 150 eyes were examined. Results In SCA3 patients CSE mRNA levels were downregulated by 36% compared to control patients (p Conclusion CSE mRNA expression in SCA3 patients is decreased. Using a Drosophila melanogaster model for SCA3, we show that manipulation of CSE expression influences the degree of eye degeneration. Possibly, a higher production of endogenous H2S underlies the protective role of CSE overexpression. In the absence of effective therapeutic interventions in the devastating course of polyglutamine disorders, manipulation of CSE might be a promising target for future interventions.