RNA-binding proteins (RBPs) play an essential role in development, normal functioning and human disease. Staufen1 (STAU1) is an RBP that regulates mRNA degradation and subcellular localization, and is part of the ATXN2 protein complex. Previously, we showed that STAU1 is overabundant in patient fibroblasts and in mouse models of Alzheimer's disease (AD), amyotrophic lateral sclerosis (ALS), and spinocerebellar ataxia type 2 (SCA2), where it is associated with impaired autophagic flux due to STAU1-mediated upregulation of mTOR translation. STAU1 overabundance and impaired autophagy cause accumulation of biomolecular condensates and abnormal unfolded protein response (UPR). We generated a mouse model expressing the entire human STAU1 gene (hSTAU1) in a bacterial artificial chromosome (BAC) construct. hSTAU1 in these mice was expressed in cerebral hemispheres, cerebellum and spinal cord, as well as cultured cortical neurons and cortical and spinal cord astrocytes and microglia. Expression of hSTAU1 caused dysregulated gene expression, abnormal autophagy, glial activation, and changes in neuronal marker proteins. All of these were significantly improved by reducing STAU1 abundance by RNAi, but exacerbated in BAC-STAU1 mice crossed with Prp-TDP-43(Q331K) transgenic mice. Similar results were also obtained in eye phenotypes in ALS- and SCA2-relevant fly models upon changing staufen-1 dosage. Despite the molecular changes, we observed no overt behavioral changes in mice up to 55 weeks of age, suggesting that STAU1 may function as an epistatic modifier of neuronal degeneration. The BAC-hSTAU1 mouse will be useful for developing therapies targeting the human STAU1 gene.

Background Christianson syndrome is an x-linked recessive neurodevelopmental and neurodegenerative condition caused by mutations to the SLC9A6 gene encoding NHE6, a sodium-hydrogen exchanger critical for regulating endosomal pH. Using an adeno-associated viral (AAV) vector targeting Purkinje cells (PHP.eB-L7-Slc9a6-GFP), we recently performed functional complementation studies to demonstrate that mutation to the rat Slc9a6 gene causes a Christianson syndrome-relevant cerebellar phenotype in the shaker rat.Methods We carried out a longitudinal study evaluating the impact of gene replacement targeting Purkinje cells on ataxia and tremor in the shaker rat. Further, in a smaller follow-up study, we tested administration of AAV9-CAG-hSLC9A6 to determine whether key molecular and motor findings could be replicated with a more clinically relevant viral construct. In both experimental cohorts, we performed molecular studies to evaluate expression of NHE6 and key cerebellar markers.Results Administration of either of PHP.eB-L7-Slc9a6-GFP or AAV9-CAG-hSLC9A6 AAV vectors led to significant improvement in both the molecular and motor phenotypes. The abundance of each disease-relevant cerebellar proteins was strongly correlated to motor ataxia, but less so to tremor. Further, while ataxia and tremor were initially strongly correlated early in the disease progression, this relationship weakened over time.Conclusions These findings impact future SLC9A6-targeted gene therapy efforts for Christianson syndrome and support gene replacement as a potentially viable therapeutic strategy. Common markers associated with cerebellar degeneration are much more strongly tied to ataxia than to tremor, indicating that ataxia may be more tied related to degenerative processes than tremor.

Staufen2 (STAU2) is an RNA-binding protein that controls mRNA trafficking and expression. Previously, we showed that its paralog, Staufen1 (STAU1), was overabundant in cellular and mouse models of neurodegenerative diseases and amyotrophic lateral sclerosis (ALS) patient spinal cord. Here, we investigated features of STAU2 that might parallel STAU1. STAU2 protein, but not mRNA, was overabundant in spinocerebellar ataxia type 2 (SCA2), ALS/frontotemporal dementia patient fibroblasts, ALS patient spinal cord tissues, and in central nervous system tissues from SCA2 and ALS animal models. Exogenous expression of STAU2 in human embryonic kidney 293 cells activated mechanistic target of rapamycin (mTOR) and stress granule formation. Targeting STAU2 by RNAi normalized mTOR in SCA2 and C9ORF72 cellular models. The microRNA miR-217, previously identified as downregulated in SCA2 mice, targets the STAU2 3'-UTR. We now demonstrate that exogenous expression of miR-217 significantly reduced STAU2 and mTOR levels in cellular models of neurodegenerative disease. These results suggest a functional link between STAU2 and mTOR signaling and identify a major role for miR-217 that could be exploited in therapeutic development.

Stress responses and neuronal death mediated by the p53 pathway play a central role in the progression of neurodegenerative disease, constituting a common target to extend neuronal function and survival. Interaction of p53 and its signaling network with RNA-binding proteins (RBPs) helps fine-tune its activation and the resulting cell fates. Preclinical therapeutics based on depletion of the RBP STAUFEN-1 (STAU1) protein successfully prevent neurodegeneration, however, the specific mechanisms are not fully understood. STAU1 is pathologically overabundant in multiple neurological disorders and contributes to neurodegeneration by exacerbating autophagy dysfunction, endoplasmic reticulum stress, and RNA-protein condensate accumulation. We previously showed that lowering STAU1 levels mitigates these disease-related features and prevents neuronal death in animal models of amyotrophic lateral sclerosis/frontotemporal dementia (ALS/FTD) and spinocerebellar ataxia type 2 (SCA2). Here, we show by combined transcriptomic and functional analyses that STAU1 reduction results in the inhibition of apoptosis through the p53 pathway. In both proliferating and post-mitotic cell types—human iPSC-derived neurons, mouse cortical neurons, SH-SY5Y cells, and fibroblasts—STAU1 reduction effectively prevented p53-mediated apoptosis and DNA damage induced by Nutlin-3 and etoposide. Further examination in C9orf72-expanded patient-derived fibroblasts and a C9orf72 mouse model of ALS/FTD, which exhibit baseline overabundance of STAU1 and activation of the p53 pathway, confirmed that STAU1 reduction also prevented p53-driven pro-apoptotic signaling. These findings establish STAU1 as a novel modulator of DNA damage and p53-dependent apoptosis, suggesting that targeting STAU1 could be a promising approach to prevent neurodegeneration in ALS/FTD.

Background:Christianson syndrome (CS) is an x-linked recessive neurodevelopmental and neurodegenerative condition characterized by severe intellectual disability, cerebellar degeneration, ataxia, and epilepsy. Mutations to the SLC9A6 gene encoding NHE6 are responsible for CS, and we recently demonstrated that a mutation to the rat Slc9a6 gene causes a similar phenotype in the spontaneous shaker rat model, which exhibits cerebellar degeneration with motor dysfunction. In previous work, we used the PhP.eB-L7-Slc9a6-GFP adeno-associated viral (AAV) vector to demonstrate that gene replacement in Purkinje cells reduced the shaker motor and molecular phenotype. Methods:We carried out a 20-week longitudinal study evaluating the impact of Purkinje cell-specific gene replacement on ataxia and tremor. Taking advantage of the high homology between human SLC9A6 and rat Slc9a6, we tested a more clinically relevant construct, AAV9-CAG-hSLC9A6 AAV vector in the shaker rat. In both experimental cohorts, we performed molecular studies to evaluate expression of NHE6 and key cerebellar markers. We then characterized the relationship between molecular markers and motor function, as well between tremor and ataxia. Results:Administration of either of PhP.eB-L7-Slc9a6-GFP or AAV9-CAG-hSLC9A6 AAV vectors led to significant improvement in the molecular and motor phenotypes. The abundance of each disease-relevant cerebellar proteins was significantly correlated to motor ataxia. Further, we found that the relationship between cerebellar ataxia and tremor devolved over time, with disease modifying therapy disrupting their temporal relationship. Conclusions:These findings impact future SLC9A6-targeted gene therapy efforts for CS and strongly support gene replacement as a viable therapeutic strategy. Furthermore, tremor and ataxia phenotypes may arise from dissociable cerebellar mechanisms.

Background and Objectives:Micro-RNAs (miRNAs) are critical for regulating the expression of genes in multiple neurodegenerative diseases, but miRNAs have not been investigated in spinocerebellar ataxia type 2 (SCA2). SCA2, a dominantly inherited progressive neurodegenerative polyglutamine (polyQ) disease, is caused by a CAG repeat expansion in the ataxin-2 (ATXN2) gene. In this study, we determined miRNA transcriptomes in SCA2-BAC-ATXN2[Q72] transgenic mice.Methods:We assessed the expression of miRNAs in SCA2 transgenic mouse cerebella using the HiSeq Illumina sequencer. We used the miRNA target filter tool in Qiagen Ingenuity Pathway Analysis (IPA) to identify target genes of differentially expressed miRNAs (DEmiRs) within in the SCA2 mouse transcriptomes and then performed pathway analyses.Results:Our analysis revealed significant changes in the expression levels of multiple miRNAs in mice with SCA2. We identified 81 DEmiRs in mice with SCA2, with 52 miRNAs upregulated and 29 miRNAs downregulated after onset of rotarod deficit. Subsequent IPA processing enabled us to establish connections between these DEmiRs and specific biological regulatory functions. Furthermore, by using the IPA miRNA target filter, we identified target genes of DEmiRs in the SCA2-BAC-ATXN2[Q72] transcriptome data set and demonstrated their significant impact on several biological functional and disease pathways.Discussion:Our study establishes the role of both DEmiRs and their targets in SCA2 pathogenesis. By expressing mutant ATXN2 under the control of its endogenous regulatory elements in the SCA2-BAC-ATXN2[Q72] mouse model, we identified a set of DEmiRs that are shared across multiple neurodegenerative diseases including other SCAs, Alzheimer disease (AD), Parkinson disease (PD), and amyotrophic lateral sclerosis (ALS). There was a significant overlap of both DEmiRs and their targets of BAC-ATXN2[Q72] transcriptomes in dysregulated pathways that characterize SCA2. This observation also extended to dysregulated pathways in ALS, AD, and PD. DEmiRs identified in this study may represent therapeutic targets for neurodegeneration or lead to biomarkers for characterizing various neurodegenerative diseases.

The shaker rat carries a naturally occurring mutation leading to progressive ataxia characterized by Purkinje cell (PC) loss. We previously reported on fine-mapping the shaker locus to the long arm of the rat X chromosome. In this work, we sought to identify the mutated gene underlying the shaker phenotype and confirm its identity by functional complementation. We fine-mapped the candidate region and analyzed cerebellar transcriptomes, identifying a XM_217630.9 (Slc9a6):c.[191_195delinsA] variant in the Slc9a6 gene that segregated with disease. We generated an adeno-associated virus (AAV) targeting Slc9a6 expression to PCs using the mouse L7-6 (L7) promoter. We administered the AAV prior to the onset of PC degeneration through intracerebroventricular injection and found that it reduced the shaker motor, molecular, and cellular phenotypes. Therefore, Slc9a6 is mutated in shaker and AAV-based gene therapy may be a viable therapeutic strategy for Christianson syndrome, also caused by Slc9a6 mutation.

ObjectiveThe mechanistic target of rapamycin (mTOR) kinase is one of the master coordinators of cellular stress responses, regulating metabolism, autophagy, and apoptosis. We recently reported that staufen1 (STAU1), a stress granule (SG) protein, was overabundant in fibroblast cell lines from patients with spinocerebellar ataxia type 2 (SCA2), amyotrophic lateral sclerosis, frontotemporal degeneration, Huntington's, Alzheimer's, and Parkinson's diseases as well as animal models, and patient tissues. STAU1 overabundance is associated with mTOR hyperactivation and links SG formation with autophagy. Our objective was to determine the mechanism of mTOR regulation by STAU1.MethodsWe determined STAU1 abundance with disease‐ and chemical‐induced cellular stressors in patient cells and animal models. We also used RNA‐binding assays to contextualize STAU1 interaction with MTOR mRNA.ResultsSTAU1 and mTOR were overabundant in bacterial artificial chromosome (BAC)‐C9ORF72, ATXN2Q127, and Thy1‐TDP‐43 transgenic mouse models. Reducing STAU1 levels in these mice normalized mTOR levels and activity and autophagy‐related marker proteins. We also saw increased STAU1 levels in HEK293 cells transfected to express C9ORF72‐relevant dipeptide repeats (DPRs). Conversely, DPR accumulations were not observed in cells treated by STAU1 RNA interference (RNAi). Overexpression of STAU1 in HEK293 cells increased mTOR levels through direct MTOR mRNA interaction, activating downstream targets and impairing autophagic flux. Targeting mTOR by rapamycin or RNAi normalized STAU1 abundance in an SCA2 cellular model.InterpretationSTAU1 interaction with mTOR drives its hyperactivation and inhibits autophagic flux in multiple models of neurodegeneration. Staufen, therefore, constitutes a novel target to modulate mTOR activity and autophagy, and for the treatment of neurodegenerative diseases. ANN NEUROL 2023;93:398–416

CAG repeat expansions in the ATXN2 (ataxin-2) gene can cause the autosomal dominant disorder spinocerebellar ataxia type 2 (SCA2) as well as increase the risk of ALS. Abnormal molecular, motor, and neurophysiological phenotypes in SCA2 mouse models are normalized by lowering ATXN2 transcription, and reduction of nonmutant Atxn2 expression has been shown to increase the life span of mice overexpressing the TDP-43 (transactive response DNA-binding protein 43 kDa) ALS protein, demonstrating the potential benefits of targeting ATXN2 transcription in humans. Here, we describe a quantitative high-throughput screen to identify compounds that lower ATXN2 transcription. We screened 428,759 compounds in a multiplexed assay using an ATXN2-luciferase reporter in human embryonic kidney 293 (HEK-293) cells and identified a diverse set of compounds capable of lowering ATXN2 transcription. We observed dose-dependent reductions of endogenous ATXN2 in HEK-293 cells treated with procillaridin A, 17-dimethylaminoethylamino-17-demethoxygeldanamycin (17-DMAG), and heat shock protein 990 (HSP990), known inhibitors of HSP90 and Na+/K+-ATPases. Furthermore, HEK-293 cells expressing polyglutamine-expanded ATXN2-Q58 treated with 17-DMAG had minimally detectable ATXN2, as well as normalized markers of autophagy and endoplasmic reticulum stress, including STAU1 (Staufen 1), molecular target of rapamycin, p62, LC3-II (microtubule-associated protein 1A/1B-light chain 3II), CHOP (C/EBP homologous protein), and phospho-eIF2α (eukaryotic initiation factor 2α). Finally, bacterial artificial chromosome ATXN2-Q22 mice treated with 17-DMAG or HSP990 exhibited highly reduced ATXN2 protein abundance in the cerebellum. Taken together, our study demonstrates inhibition of HSP90 or Na+/K+-ATPases as potentially effective therapeutic strategies for treating SCA2 and ALS.

ABSTRACTStaufen1 (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 abundancein vivoby 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 theSTAU1mRNA 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 abundancein vivoin a new BAC-STAU1 mouse model. This identified efficacious ASOs targeting humanSTAU1 in vivothat normalized autophagy marker proteins, including ASO-45 that also targets mouseStau1. 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 ofThy1-TDP-43 transgenic mice. TargetingSTAU1may be an effective strategy for treating ALS and SCA2 as well as other disorders characterized by its overabundance.

Parkinson's disease (PD) is a progressive neurodegenerative disorder caused by loss of dopaminergic neurons of the substantia nigra. The hallmark of PD is the appearance of neuronal protein aggregations known as Lewy bodies and Lewy neurites, of which α-synuclein forms a major component. Familial PD is rare and is associated with missense mutations of the SNCA gene or increases in gene copy number resulting in SNCA overexpression. This suggests that lowering SNCA expression could be therapeutic for PD. Supporting this hypothesis, SNCA reduction was neuroprotective in cell line and rodent PD models. We developed novel cell lines expressing SNCA fused to the reporter genes luciferase (luc) or GFP with the objective to enable high-throughput compound screening (HTS) for small molecules that can lower SNCA expression. Because SNCA expression is likely regulated by far-upstream elements (including the NACP-REP1 located at 8852 bp upstream of the transcription site), we employed zinc finger nuclease (ZFN) genome editing to insert reporter genes in-frame downstream of the SNCA gene in order to retain native SNCA expression control. This ensured full retention of known and unknown up- and downstream genetic elements controlling SNCA expression. Treatment of cells with the histone deacetylase inhibitor valproic acid (VPA) resulted in significantly increased SNCA-luc and SNCA-GFP expression supporting the use of our cell lines for identifying small molecules altering complex modes of expression control. Cells expressing SNCA-luc treated with a luciferase inhibitor or SNCA siRNA resulted in Z'-scores ≥ 0.75, suggesting the suitability of these cell lines for use in HTS. This study presents a novel use of genome editing for the creation of cell lines expressing α-synuclein fusion constructs entirely under native expression control. These cell lines are well suited for HTS for compounds that lower SNCA expression directly or by acting at long-range sites to the SNCA promoter and 5'-UTR.

Staufen-1 (STAU1) is an RNA-binding protein that becomes highly overabundant in numerous neurodegenerative disease models, including those carrying mutations in presenilin1 (PSEN1), microtubule-associated protein tau ( MAPT ), huntingtin ( HTT ), TAR DNA-binding protein-43 gene ( TARDBP ), or C9orf72. We previously reported that elevations in STAU1 determine autophagy defects and its knockdown is protective in models of several neurodegenerative diseases. Additional functional consequences of STAU1 overabundance, however, have not been investigated. We studied the role of STAU1 in the chronic activation of the unfolded protein response (UPR), a common feature among neurodegenerative diseases and often directly associated with neuronal death. Here we report that STAU1 is a novel modulator of the UPR, and is required for apoptosis induced by activation of the PERK–CHOP pathway. STAU1 levels increased in response to multiple endoplasmic reticulum (ER) stressors, and exogenous expression of STAU1 was sufficient to cause apoptosis through the PERK–CHOP pathway of the UPR. Cortical neurons and skin fibroblasts derived from Stau1 −/− mice showed reduced UPR and apoptosis when challenged with thapsigargin. In fibroblasts from individuals with SCA2 or with ALS-causing TDP-43 and C9ORF72 mutations, we found highly increased STAU1 and CHOP levels in basal conditions, and STAU1 knockdown restored CHOP levels to normal. Taken together, these results show that STAU1 overabundance reduces cellular resistance to ER stress and precipitates apoptosis.

PURPOSE:Newborn screening disorders increasingly require genetic variant analysis as part of second-tier or confirmatory testing. Sanger sequencing and gene-specific next-generation sequencing (NGS)-based tests, the current methods of choice, are costly and lack scalability when expanding to new conditions. We describe a scalable, exome sequencing-based NGS pipeline with a priori analysis restriction that can be universally applied to any NBS disorder.METHODS:De-identified abnormal newborn screening specimens representing severe combined immune deficiency (SCID), cystic fibrosis (CF), VLCAD deficiency, metachromatic leukodystrophy (MLD), and in silico sequence read data sets were used to validate the pipeline. To support interpretation and clinical decision-making within the bioinformatics pipeline, variants from multiple databases were curated and validated.RESULTS:CFTR variant panel analysis correctly identified all variants. Concordance compared with diagnostic testing results for targeted gene analysis was between 78.6% and 100%. Validation of the bioinformatics pipeline with in silico data sets revealed a 100% detection rate. Varying degrees of overlap were observed between ClinVar and other databases ranging from 3% to 65%. Data normalization revealed that 11% of variants across the databases required manual curation.CONCLUSION:This pipeline allows for restriction of analysis to variants within a single gene or multiple genes, and can be readily expanded to full exome analysis if clinically indicated and parental consent is granted.

ObjectiveMutations in the ATXN2 gene (CAG expansions ≥32 repeats) can be a rare cause of Parkinson's disease and amyotrophic lateral sclerosis (ALS). We recently reported that the stress granule (SG) protein Staufen1 (STAU1) was overabundant in neurodegenerative disorder spinocerebellar ataxia type 2 (SCA2) patient cells, animal models, and ALS‐TDP‐43 fibroblasts, and provided a link between SG formation and autophagy. We aimed to test if STAU1 overabundance has a role in the pathogenesis of other neurodegenerative diseases.MethodsWith multiple neurodegenerative patient‐derived cell models, animal models, and human postmortem ALS tissue, we evaluate STAU1 function using biochemical and immunohistological analyses.ResultsWe demonstrate STAU1 overabundance and increased total and phosphorylated mammalian target of rapamycin (mTOR) in fibroblast cells from patients with ALS with mutations in TDP‐43, patients with dementia with PSEN1 mutations, a patient with parkinsonism with MAPT mutation, Huntington's disease (HD) mutations, and SCA2 mutations. Increased STAU1 levels and mTOR activity were seen in human ALS spinal cord tissues as well as in animal models. Changes in STAU1 and mTOR protein levels were post‐transcriptional. Exogenous expression of STAU1 in wildtype cells was sufficient to activate mTOR and downstream targets and form SGs. Targeting STAU1 by RNAi normalized mTOR, suggesting a potential role for therapy in diseases associated with STAU1 overabundance.InterpretationSTAU1 overabundance in neurodegeneration is a common phenomenon associated with hyperactive mTOR. Targeting STAU1 with ASOs or miRNA viral vectors may represent a novel, efficacious therapy for neurodegenerative diseases characterized by overabundant STAU1. ANN NEUROL 2021;89:1114–1128

Accumulation of α-synuclein is a main underlying pathological feature of Parkinson's disease and α-synucleinopathies, for which lowering expression of the α-synuclein gene (SNCA) is a potential therapeutic avenue. Using a cell-based luciferase reporter of SNCA expression we performed a quantitative high-throughput screen of 155,885 compounds and identified A-443654, an inhibitor of the multiple functional kinase AKT, as a potent inhibitor of SNCA. HEK-293 cells with CAG repeat expanded ATXN2 (ATXN2-Q58 cells) have increased levels of α-synuclein. We found that A-443654 normalized levels of both SNCA mRNA and α-synuclein monomers and oligomers in ATXN2-Q58 cells. A-443654 also normalized levels of α-synuclein in fibroblasts and iPSC-derived dopaminergic neurons from a patient carrying a triplication of the SNCA gene. Analysis of autophagy and endoplasmic reticulum stress markers showed that A-443654 successfully prevented α-synuclein toxicity and restored cell function in ATXN2-Q58 cells, normalizing the levels of mTOR, LC3-II, p62, STAU1, BiP, and CHOP. A-443654 also decreased the expression of DCLK1, an inhibitor of α-synuclein lysosomal degradation. Our study identifies A-443654 and AKT inhibition as a potential strategy for reducing SNCA expression and treating Parkinson's disease pathology.

The objective of this work is to optimize a gene therapeutic treatment strategy in the Wistar Furth Shaker rat, a spontaneous model of ataxia caused by Slc9a6 mutation.

Selective neuronal vulnerability in neurodegenerative disease is poorly understood. Using the ATXN1[82Q] model of spinocerebellar ataxia type 1 (SCA1), we explored the hypothesis that regional differences in Purkinje neuron degeneration could provide novel insights into selective vulnerability. ATXN1[82Q] Purkinje neurons from the anterior cerebellum were found to degenerate earlier than those from the nodular zone, and this early degeneration was associated with selective dysregulation of ion channel transcripts and altered Purkinje neuron spiking. Efforts to understand the basis for selective dysregulation of channel transcripts revealed modestly increased expression of the ATXN1 co-repressor Capicua (Cic) in anterior cerebellar Purkinje neurons. Importantly, disrupting the association between ATXN1 and Cic rescued the levels of these ion channel transcripts, and lentiviral overexpression of Cic in the nodular zone accelerated both aberrant Purkinje neuron spiking and neurodegeneration. These findings reinforce the central role for Cic in SCA1 cerebellar pathophysiology and suggest that only modest reductions in Cic are needed to have profound therapeutic impact in SCA1.

The spinocerebellar ataxia type 2 (SCA2) gene ATXN2 has a prominent role in the pathogenesis and treatment of amyotrophic lateral sclerosis (ALS). In addition to cerebellar ataxia, motor neuron disease is often seen in SCA2, and ATXN2 CAG repeat expansions in the long normal range increase ALS risk. Also, lowering ATXN2 expression in TDP-43 ALS mice prolongs their survival. Here we investigated the ATXN2 relationship with motor neuron dysfunction in vivo by comparing spinal cord (SC) transcriptomes reported from TDP-43 and SOD1 ALS mice and ALS patients with those from SCA2 mice. SC transcriptomes were determined using an SCA2 bacterial artificial chromosome mouse model expressing polyglutamine expanded ATXN2. SCA2 cerebellar transcriptomes were also determined, and we also investigated the modification of gene expression following treatment of SCA2 mice with an antisense oligonucleotide (ASO) lowering ATXN2 expression. Differentially expressed genes (DEGs) defined three interconnected pathways (innate immunity, fatty acid biosynthesis and cholesterol biosynthesis) in separate modules identified by weighted gene co-expression network analysis. Other key pathways included the complement system and lysosome/phagosome pathways. Of all DEGs in SC, 12.6% were also dysregulated in the cerebellum. Treatment of mice with an ATXN2 ASO also modified innate immunity, the complement system and lysosome/phagosome pathways. This study provides new insights into the underlying molecular basis of SCA2 SC phenotypes and demonstrates annotated pathways shared with TDP-43 and SOD1 ALS mice and ALS patients. It also emphasizes the importance of ATXN2 in motor neuron degeneration and confirms ATXN2 as a therapeutic target.

Purpose Metachromatic leukodystrophy (MLD) is a lysosomal storage disorder caused by the deficiency of arylsulfatase A (ARSA), which results in the accumulation of sulfatides. Newborn screening for MLD may be considered in the future as innovative treatments are advancing. We carried out a research study to assess the feasibility of screening MLD using dried blood spots (DBS) from de-identified newborns. Methods To minimize the false-positive rate, a two-tier screening algorithm was designed. The primary test was to quantify C16:0-sulfatide in DBS by ultraperformance liquid chromatography–tandem mass spectrometry (UPLC-MS/MS). The screening cutoff was established based on the results from 15 MLD newborns to achieve 100% sensitivity. The secondary test was to measure the ARSA activity in DBS from newborns with abnormal C16:0-sulfatide levels. Only newborns that displayed both abnormal C16:0-sulfatide abundance and ARSA activity were considered screen positives. Results A total of 27,335 newborns were screened using this two-tier algorithm, and 2 high-risk cases were identified. ARSA gene sequencing identified these two high-risk subjects to be a MLD-affected patient and a heterozygote. Conclusion Our study demonstrates that newborn screening for MLD is highly feasible in a real-world scenario with near 100% assay specificity.