ULK overexpression mitigates motor deficits and neuropathology in mouse models of Machado-Joseph disease

Abstract

Machado-Joseph disease (MJD) is a fatal neurodegenerative disorder clinically characterized by prominent ataxia. It is caused by an expansion of a CAG trinucleotide in ATXN3, translating into an expanded polyglutamine (polyQ) tract in the ATXN3 protein, that becomes prone to misfolding and aggregation. The pathogenesis of the disease has been associated with the dysfunction of several cellular mechanisms, including autophagy and transcription regulation. In this study, we investigated the transcriptional modifications of the autophagy pathway in models of MJD and assessed whether modulating the levels of the affected autophagy-associated transcripts (AATs) would alleviate MJD-associated pathology. Our results show that autophagy is impaired at the transcriptional level in MJD, affecting multiple AATs, including Unc-51 like autophagy activating kinase 1 and 2 (ULK1 and ULK2), two homologs involved in autophagy induction. Reinstating ULK1/2 levels by adeno-associated virus (AAV)-mediated gene transfer significantly improved motor performance while preventing neuropathology in two in vivo models of MJD. Moreover, in vitro studies showed that the observed positive effects may be mainly attributed to ULK1 activity. This study provides strong evidence of the beneficial effect of overexpression of ULK homologs, suggesting these as promising instruments for the treatment of MJD and other neurodegenerative disorders.

Keywords: Machado-Joseph disease; Spinocerebellar Ataxia Type 3; Unc-51 like autophagy activating kinase 1 and 2; adeno-associated viral vectors; ataxin-3; autophagy; gene therapy; motor improvements; neuroprotection; transcriptional dysregulation.