Small non-coding RNA content in plasma-derived extracellular vesicles distinguish ataxic SCA3 mutation carriers from pre-ataxic and control subjects

Spinocerebellar ataxia type 3 (SCA3), a neurodegenerative disorder caused by a CAG expansion in the ATXN3 gene, is the most common spinocerebellar ataxia subtype worldwide. Currently, there is no therapy to stop or prevent disease progression. Promising therapeutic strategies are emerging, but their translation into clinical practice requires sensitive and reliable biomarkers. Blood circulating extracellular vesicles constitute a promising source of biomarkers with potential to track alterations of the central nervous system due to their ability to cross the blood brain barrier. Here, we perform sequencing analysis of small RNAs from plasma-derived extracellular vesicles from SCA3 mutation carriers (10 pre-ataxic and 10 ataxic) and 12 control subjects to identify potential RNA biomarker candidates for this disease. Data showed that plasma-derived extracellular vesicles from ataxic SCA3 mutation carriers are enriched in mitochondrial, nuclear, and nucleolar RNA biotypes compared to pre-ataxic and control subjects. Moreover, ataxic mutation carriers could be discriminated from control and pre-ataxic subjects based on the miRNAs or piRNAs content, but not tRNA. Furthermore, we identified a subset of differentially expressed miRNAs and piRNAs that clearly differentiate ataxic mutation carriers from pre-ataxic and control subjects. These findings open new avenues for further investigation on the role of these RNAs in the pathogenesis of SCA3 and their potential as biomarkers for this disease. ### Competing Interest Statement TK, MS, BvdW are members of the European Reference Network for Rare Neurological Diseases (ERN-RD, project number 739510). PS and MMP were supported by FCT under the fellowship grants SFRH/BD/148451/2019 and 2022.11089.BD, respectively. TMM was supported by a fellowship from the BioSys PhD programme PD65-2012 (PD/BD/142854/2018) also from FCT. MR is supported by FCT CEECIND/03018/2018. PG and HGM work at University College London Hospitals/University College London, which receives a proportion of funding from the Department of Health National Institute for Health Research Biomedical Research Centre funding scheme. PG received funding from the Medical Research Council (MR/N028767/1) and CureSCA3 in support of HGM work. JF received funding as a fellow of the Hertie Network of Excellence in Clinical Neuroscience. MS has received consultancy honoraria from Janssen, Ionis, Orphazyme, Servier, Reata, GenOrph, and AviadoBio, all unrelated to the present manuscript. LPA research group has received private funding from PTC Therapeutics, Uniqure, Wave life Sciences, Servier, Blade Therapeutics and Hoffmann-La Roche AG outside the submitted work. Radboud University Medical Center (through BvdW) has received consultancy fees from Servier and Biohaven, and BvdW serves on a scientific advisory board of Vico Therapeutics. PG has received grants and honoraria for advisory board from Vico Therapeutics, honoraria for advisory board from Triplet Therapeutics, grants and personal fees from Reata Pharmaceutical, grants from Wave.