412. A Novel Friedreich's Ataxia Model and In Vivo Gene Rescue Using HSV-1 Amplicon Vectors in Transgenic Mice

There is currently no effective cure or treatment for Friedreich's ataxia (FA), the most common of the hereditary ataxias. The disease is caused by mutations in FRDA, the frataxin gene, which result in drastically reduced expression levels. In whole animal models, one of the key difficulties in mimicking the human disease is obtaining the precise levels of frataxin expression with the appropriate tissue distribution to provoke pathology but not result in lethality. In order to develop strategies to circumvent these problems, conditional (floxed) frataxin transgenic mice have been generated by the laboratory of Helene Puccio and Michel Koenig (Strassbourg). We have generated CRE-expressing HSV-1 amplicon vectors and present results showing loss of frataxin protein levels in neurons from these loxP[frda] mice infected by these vectors. Using stereotactic injection, we have also achieved in vivo delivery of these CRE-expressing vectors into the olivocerebellar circuit of loxP[frda] mice to generate a localised gene knockout model. These mice develop a behavioural deficit in the rotarod assay detectable after 4 weeks, and with a stable difference with respect to lacZ vector-injected control mice up to the latest time point measured (16 weeks). We have also generated viral vectors expressing human frataxin cDNA and present results showing correction of this ataxic phenotype in our novel FA model. When frataxin-expressing vectors were injected into mice rendered ataxic 4 weeks previously, behavioural recovery was detectable as soon as 4 weeks after the second injection and with a stable difference up to 12 weeks with respect to mice re-injected with lacZ vector. Our novel FA mouse model and our successful in vivo gene rescue strategy will serve to rapidly and specifically address the neurological aspects of this neurodegenerative disease, both in understanding the pathogenic mechanisms as well as developing therapies.