Widespread alternative splicing dysregulation occurs presymptomatically in CAG expansion spinocerebellar ataxias.

The spinocerebellar ataxias (SCAs) are a group of dominantly inherited neurodegenerative diseases, several of which are caused by CAG expansion mutations (SCAs 1, 2, 3, 6, 7 and 12) and more broadly belong to the large family of over 40 microsatellite expansion diseases. While dysregulation of alternative splicing is a well defined driver of disease pathogenesis across several microsatellite diseases, the contribution of alternative splicing in CAG expansion SCAs is poorly understood. Furthermore, despite extensive studies on differential gene expression, there remains a gap in our understanding of presymptomatic transcriptomic drivers of disease. We sought to address these knowledge gaps through a comprehensive study of 29 publicly available RNA-sequencing datasets. We identified that dysregulation of alternative splicing is widespread across CAG expansion mouse models of SCAs 1, 3 and 7. These changes were detected presymptomatically, persisted throughout disease progression, were repeat length-dependent, and were present in brain regions implicated in SCA pathogenesis including the cerebellum, pons and medulla. Across disease progression, changes in alternative splicing occurred in genes that function in pathways and processes known to be impaired in SCAs, such as ion channels, synaptic signalling, transcriptional regulation and the cytoskeleton. We validated several key alternative splicing events with known functional consequences, including Trpc3 exon 9 and Kcnma1 exon 23b, in the Atxn1154Q/2Q mouse model. Finally, we demonstrated that alternative splicing dysregulation is responsive to therapeutic intervention in CAG expansion SCAs with Atxn1 targeting antisense oligonucleotide rescuing key splicing events. Taken together, these data demonstrate that widespread presymptomatic dysregulation of alternative splicing in CAG expansion SCAs may contribute to disease onset, early neuronal dysfunction and may represent novel biomarkers across this devastating group of neurodegenerative disorders.

A non-enzymatic test for SARS-CoV-2 RNA using DNA nanoswitches.

The emergence of a highly contagious novel coronavirus in 2019 led to an unprecedented need for large scale diagnostic testing. The associated challenges including reagent shortages, cost, deployment delays, and turnaround time have all highlighted the need for an alternative suite of low-cost tests. Here, we demonstrate a diagnostic test for SARS-CoV-2 RNA that provides direct detection of viral RNA and eliminates the need for costly enzymes. We employ DNA nanoswitches that respond to segments of the viral RNA by a change in shape that is readable by gel electrophoresis. A new multi-targeting approach samples 120 different viral regions to improve the limit of detection and provide robust detection of viral variants. We apply our approach to a cohort of clinical samples, positively identifying a subset of samples with high viral loads. Since our method directly detects multiple regions of viral RNA without amplification, it eliminates the risk of amplicon contamination and renders the method less susceptible to false positives. This new tool can benefit the COVID-19 pandemic and future emerging outbreaks, providing a third option between amplification-based RNA detection and protein antigen detection. Ultimately, we believe this tool can be adapted both for low-resource onsite testing as well as for monitoring viral loads in recovering patients.

Population genetic data for 21 autosomal STR loci in the Azerbaijani population using the Globalfiler™ kit.

The Republic of Azerbaijan is located in the southern Caucasus mountains, a region which is linguistically and ethnically diverse. We report allele frequency data for 21 autosomal loci from the Globalfiler™ kit in the Azerbaijani population using 467 individuals from Baku. Exact tests for Hardy Weinberg Equilibrium and Linkage Equilibrium were conducted, and all forensic parameters were estimated. High levels of Expected Heterozygosity HE were seen, with a minimum of 0.637 for TPOX and a maximum of 0.949 for SE33. Polymorphism Information Content (PIC) values for all STR loci were high, ranging from 0.587 for TPOX to 0.947 for SE33. Matching probability (MP) estimates ranged from 0.006 for SE33 to 0.178 for TPOX. Power of Discrimination (PD) values for most of the tested loci (17/21) were ≥ 0.9. The Combined Matching Probability (CMP) and the Combined Power of Discrimination (CPD) for all 21 loci were 7.84 × 10-27 and 1.0 respectively. Exact tests for population differentiation using all available Globalfiler™ datasets from across Europe and Asia reveal a general trend of higher differentiation with increasing geographical separation, but there is a need for additional population data from neighboring regions of Azerbaijan.