Targeting Staufen 1 with antisense oligonucleotides for treating ALS and SCA2

Staufen1 (STAU1) is a multifunctional RNA binding protein that controls mRNA degradation and subcellular localization. STAU1 interacts with the ATXN2 protein, that is polyglutamine expanded in spinocerebellar ataxia type 2 (SCA2). We previously showed that STAU1 is elevated and aggregated in cells from SCA2 patients, cells from amyotrophic lateral sclerosis (ALS) patients, and in SCA2 and ALS mouse models. We also found that reduction of STAU1 abundance in vivo by genetic interaction improved motor behavior in an SCA2 mouse model, normalized the levels of several SCA2-related proteins, and reduced aggregation of polyglutamine-expanded ATXN2. Here we developed antisense oligonucleotides (ASOs) lowering STAU1 expression toward developing a therapeutic that may be effective for treating SCA2 and ALS. We performed a screen of 118 20mer phosphorothioate 2-O-methoxyethyl (MOE) ASO gapmers targeting across the STAU1 mRNA coding region for lowering STAU1 expression in HEK-293 cells. ASO hits lowering STAU1 by >45 % were rescreened in SCA2 patient fibroblasts, and 10 of these were tested for lowering STAU1 abundance in vivo in a new BAC-STAU1 mouse model. This identified efficacious ASOs targeting human STAU1 in vivo that normalized autophagy marker proteins, including ASO-45 that also targets mouse Stau1. When delivered by intracerebroventricular (ICV) injection, ASO-45 normalized autophagy markers and abnormal mRNA abundances in cerebella of ATXN2-Q127 SCA2 mice, as well as ChAT, NeuN and cleaved caspase-3 in spinal cord of Thy1- TDP-43 transgenic mice. Targeting STAU1 may be an effective strategy for treating ALS and SCA2 as well as other disorders characterized by its overabundance.