Fragile X-related tremor/ataxia syndrome (FXTAS) is a neurodegenerative disease caused by CGG triplet repeat expansions in FMR1, which elicit repeat-associated non-AUG (RAN) translation and produce the toxic protein FMRpolyG. We show that FMRpolyG interacts with pathogenic CGG repeat-derived RNA G-quadruplexes (CGG-G4RNA), propagates cell to cell, and induces neuronal dysfunction. The FMRpolyG polyglycine domain has a prion-like property, preferentially binding to CGG-G4RNA. Treatment with 5-aminolevulinic acid, which is metabolized to protoporphyrin IX, inhibited RAN translation of FMRpolyG and CGG-G4RNA–induced FMRpolyG aggregation, ameliorating aberrant synaptic plasticity and behavior in FXTAS model mice. Thus, we present a novel therapeutic strategy to target G4RNA prionoids.
The most common form of DNA is a right-handed helix or the B-form DNA. DNA can also adopt a variety of alternative conformations, non-B-form DNA secondary structures, including the DNA G-quadruplex (DNA-G4). Furthermore, besides stem-loops that yield A-form double-stranded RNA, non-canonical RNA G-quadruplex (RNA-G4) secondary structures are also observed. Recent bioinformatics analysis of the whole-genome and transcriptome obtained using G-quadruplex–specific antibodies and ligands, revealed genomic positions of G-quadruplexes. In addition, accumulating evidence pointed to the existence of these structures under physiologically- and pathologically-relevant conditions, with functional roles in vivo. In this review, we focused on DNA-G4 and RNA-G4, which may have important roles in neuronal function, and reveal mechanisms underlying neurological disorders related to synaptic dysfunction. In addition, we mention the potential of G-quadruplexes as therapeutic targets for neurological diseases.
Introduction/Objective: In most cases, abnormal cardiac 123I-meta-iodobenzylguanidine (MIBG) scintigraphy increases the probability of a diagnosis of Parkinson’s disease (PD) in patients with parkinsonian features. In our study, we validated the additional value of 123I-MIBG scintigraphy beyond providing information on neurological findings and response to dopaminergic therapy for the diagnosis of PDin the early phase. Methods: We investigated 77 cases of PD (Hoehn and Yahr Stages I–III) and 73 cases of atypical parkinsonian disorder (APD), including 35 patients with multiple system atrophy, 19 with corticobasal syndrome, and 19 with progressive supranuclear palsy. Two multiple logistic regression models were developed to predict the probability of PD based on APD. Common covariates were resting tremor, vertical supranuclear palsy, apraxia, cerebellar symptoms, and response to dopaminergic therapy with MIBG scintigraphy (reference model) or without it (MIBG-added model). The net reclassification index (NRI) was examined and net benefit using decision curve analysis was performed to examine the additional clinical value of MIBG scintigraphy. Finally, we estimated the cost-effectiveness of MIBG scintigraphy. Results: The MIBG-added model significantly improved the ability to classify PD or APD compared with the reference model (NRI index 1.390, p < 0.001). However, the decision curve of the reference model ranked equally with the MIBG-added model up to a risk threshold of 0.8. In addition, MIBG scintigraphy was not cost-effective. Conclusions: Although MIBG scintigraphy has statistical usefulness for PD diagnosis, there may be little additional benefit in the early phase of PD beyond the neurological findings and response to dopaminergic therapy regarding clinical effectiveness and cost-effectiveness. It may be of greatest value when neurological findings that do not match PD are observed during the clinical course.
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