Rui Jorge Gonçalves Pereira Nobre - CNC, University of Coimbra
Title: Non-invasive silencing of mutant ataxin-3 alleviates motor and neuropathological deficits in a transgenic mouse model of Machado- Joseph disease
Abstract:
Machado-Joseph disease (MJD) is the most common dominantly-inherited ataxia. It is associated with the expansion of a (CAG)n tract in the coding region of the MJD1/ATXN3 gene. This abnormal over-repetition is translated into an expanded polyglutamine tract within ataxin-3, conferring toxic properties to this protein and resulting in severe clinical features. Although there is no medical treatment, several preclinical studies have demonstrated that silencing mutant ataxin-3 expression using RNA interference (RNAi) is a promising therapeutic approach for MJD. Our group showed that intracranial injection of viral vectors targeting mutant ataxin-3 significantly decreases the severity of the neuropathological abnormalities in rodent models of MJD (Alves et al., 2008, 2010; Nóbrega et al., 2013). However, this is an invasive procedure, which is associated with potential adverse effects and a limited vector distribution in the brain.
The present study aimed to develop a non-invasive strategy to deliver RNA interference-based treatments to the brain by intravenous (iv) injection.
For that, we used adeno-associated viral vector serotype 9 (AAV9), a vector that has a remarkable ability to bypass the blood-brain barrier (BBB) and transduce the central nervous system of mammals. AAV9 vectors encoding an artificial microRNA that targets the mutant form of ataxin-3 mRNA (AAV9-mirATAX3)
were firstly generated. Their efficacy and specificity were tested in neuronal cell models and the therapeutic potential was then evaluated in a severely impaired transgenic mouse model of MJD. Mice were intravenously injected at postnatal (PN) day one (PN1); they were submitted to behavioral tests at 3 different ages and were sacrificed at PN95.
We observed that AAV9-mirATAX3 vectors efficiently spread throughout the brain, transducing regions affected in MJD. Moreover, AAV9-mirATAX3’s treatment reduced the number of protein aggregates and cerebellar neuropathology, leading to significant improvements in all behavioral tests.
Overall, this study generated compelling evidences that a single systemic administration of the AAV9 system at postnatal day one is able to transpose the BBB, to transduce the brain of MJD mice, to silence mutant ataxin-3 in some cerebellar regions, and to alleviation of MJD motor phenotype and neuropathology.
Title: Non-invasive silencing of mutant ataxin-3 alleviates motor and neuropathological deficits in a transgenic mouse model of Machado- Joseph disease
Abstract:
Machado-Joseph disease (MJD) is the most common dominantly-inherited ataxia. It is associated with the expansion of a (CAG)n tract in the coding region of the MJD1/ATXN3 gene. This abnormal over-repetition is translated into an expanded polyglutamine tract within ataxin-3, conferring toxic properties to this protein and resulting in severe clinical features. Although there is no medical treatment, several preclinical studies have demonstrated that silencing mutant ataxin-3 expression using RNA interference (RNAi) is a promising therapeutic approach for MJD. Our group showed that intracranial injection of viral vectors targeting mutant ataxin-3 significantly decreases the severity of the neuropathological abnormalities in rodent models of MJD (Alves et al., 2008, 2010; Nóbrega et al., 2013). However, this is an invasive procedure, which is associated with potential adverse effects and a limited vector distribution in the brain.
The present study aimed to develop a non-invasive strategy to deliver RNA interference-based treatments to the brain by intravenous (iv) injection.
For that, we used adeno-associated viral vector serotype 9 (AAV9), a vector that has a remarkable ability to bypass the blood-brain barrier (BBB) and transduce the central nervous system of mammals. AAV9 vectors encoding an artificial microRNA that targets the mutant form of ataxin-3 mRNA (AAV9-mirATAX3)
were firstly generated. Their efficacy and specificity were tested in neuronal cell models and the therapeutic potential was then evaluated in a severely impaired transgenic mouse model of MJD. Mice were intravenously injected at postnatal (PN) day one (PN1); they were submitted to behavioral tests at 3 different ages and were sacrificed at PN95.
We observed that AAV9-mirATAX3 vectors efficiently spread throughout the brain, transducing regions affected in MJD. Moreover, AAV9-mirATAX3’s treatment reduced the number of protein aggregates and cerebellar neuropathology, leading to significant improvements in all behavioral tests.
Overall, this study generated compelling evidences that a single systemic administration of the AAV9 system at postnatal day one is able to transpose the BBB, to transduce the brain of MJD mice, to silence mutant ataxin-3 in some cerebellar regions, and to alleviation of MJD motor phenotype and neuropathology.