Electrical impedance tomography as a bedside assessment tool for COPD treatment during hospitalization.

For patients with chronic obstructive pulmonary disease (COPD), the assessment of the treatment efficacy during hospitalization is of importance to the optimization of clinical treatments. Conventional spirometry might not be sensitive enough to capture the regional lung function development. The study aimed to evaluate the feasibility of using electrical impedance tomography (EIT) as an objective bedside evaluation tool for the treatment of acute exacerbation of COPD (AECOPD). Consecutive patients who required hospitalization due to AECOPD were included prospectively. EIT measurements were conducted at the time of admission and before the discharge simultaneously when a forced vital capacity maneuver was conducted. EIT-based heterogeneity measures of regional lung function were calculated based on the impedance changes over time. Surveys for attending doctors and patients were designed to evaluate the ease of use, feasibility, and overall satisfaction level to understand the acceptability of EIT measurements. Patient-reported outcome assessments were conducted. User's acceptance of EIT technology was investigated with a five-dimension survey. A total of 32 patients were included, and 8 patients were excluded due to the FVC maneuver not meeting the ATS criteria. Spirometry-based lung function was improved during hospitalization but not significantly different (FEV1 %pred.: 35.8% ± 6.7% vs. 45.3% ± 8.8% at admission vs. discharge; p = 0.11. FVC %pred.: 67.8% ± 0.4% vs. 82.6% ± 5.0%; p = 0.15. FEV1/FVC: 0.41 ± 0.09 vs. 0.42 ± 0.07, p = 0.71). The symptoms of COPD were significantly improved, but the correlations between the improvement of symptoms and spirometry FEV1 and FEV1/FVC were low (R = 0.1 and -0.01, respectively). The differences in blood gasses and blood tests were insignificant. All but one EIT-based regional lung function parameter were significantly improved after hospitalization. The results highly correlated with the patient-reported outcome assessment (R > 0.6, p < 0.001). The overall acceptability score of EIT measurement for both attending physicians and patients was high (4.1 ± 0.8 for physicians, 4.5 ± 0.5 for patients out of 5). These results demonstrated that it was feasible and acceptable to use EIT as an objective bedside evaluation tool for COPD treatment efficacy.

DDX3X overexpression decreases dipeptide repeat proteins in a mouse model of C9ORF72-ALS/FTD.

Hexanucleotide repeat expansion in C9ORF72 (C9) is the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). One of the proposed pathogenic mechanisms is the neurotoxicity arising from dipeptide repeat (DPR) proteins produced by repeat-associated non-AUG (RAN) translation. Therefore, reducing DPR levels emerges as a potential therapeutic strategy for C9ORF72-ALS/FTD. We previously identified an RNA helicase, DEAD-box helicase 3 X-linked (DDX3X), modulates RAN translation. DDX3X overexpression decreases poly-GP accumulation in C9ORF72-ALS/FTD patient-derived induced pluripotent stem cell (iPSC)-differentiated neurons (iPSNs) and reduces the glutamate-induced neurotoxicity. In this study, we examined the in vivo efficacy of DDX3X overexpression using a mouse model. We expressed exogenous DDX3X or GFP in the central nervous system (CNS) of the C9-500 ALS/FTD BAC transgenic or non-transgenic control mice using adeno-associated virus serotype 9 (AAV9). The DPR levels were significantly reduced in the brains of DDX3X-expressing C9-BAC mice compared to the GFP control even twelve months after virus delivery. Additionally, p62 aggregation was also decreased. No neuronal loss or neuroinflammatory response were detected in the DDX3X overexpressing C9-BAC mice. This work demonstrates that DDX3X overexpression effectively reduces DPR levels in vivo without provoking neuroinflammation or neurotoxicity, suggesting the potential of increasing DDX3X expression as a therapeutic strategy for C9ORF72-ALS/FTD.

Exploring the brain epitranscriptome: perspectives from the NSAS summit.

Increasing evidence reinforces the essential function of RNA modifications in development and diseases, especially in the nervous system. RNA modifications impact various processes in the brain, including neurodevelopment, neurogenesis, neuroplasticity, learning and memory, neural regeneration, neurodegeneration, and brain tumorigenesis, leading to the emergence of a new field termed neuroepitranscriptomics. Deficiency in machineries modulating RNA modifications has been implicated in a range of brain disorders from microcephaly, intellectual disability, seizures, and psychiatric disorders to brain cancers such as glioblastoma. The inaugural NSAS Challenge Workshop on Brain Epitranscriptomics hosted in Crans-Montana, Switzerland in 2023 assembled a group of experts from the field, to discuss the current state of the field and provide novel translational perspectives. A summary of the discussions at the workshop is presented here to simulate broader engagement from the general neuroscience field.

[Medicinal plant resources in Inner Mongolia autonomous region of China and Mongolia: a comparative study].

Inner Mongolia autonomous region of China and Mongolia are the primary regions where Chinese and Mongolian medicine and its medicinal plant resources are distributed. In this study, 133 families, 586 genera, and 1 497 species of medicinal plants in Inner Mongolia as well as 62 families, 261 genera, and 467 species of medicinal plants in Mongolia were collected through field investigation, specimen collection and identification, and literature research. And the species, geographic distribution, and influencing factors of the above medicinal plants were analyzed. The results revealed that there were more plant species utilized for medicinal reasons in Inner Mongolia than in Mongolia. Hotspots emerged in Hulunbuir, Chifeng, and Tongliao of Inner Mongolia, while there were several hotspots in Eastern province, Sukhbaatar province, Gobi Altai province, Bayankhongor province, Middle Gobi province, Kobdo province, South Gobi province, and Central province of Mongolia. The interplay of elevation and climate made a non-significant overall contribution to the diversity of plant types in Inner Mongolia and Mongolia. The contribution of each factor increased significantly when the vegetation types of Inner Mongolia and Mongolia were broadly divided into forest, grassland and desert. Thus, the distribution of medicinal plant resources and vegetation cover were jointly influenced by a variety of natural factors such as topography, climate and interactions between species, and these factors contributed to and constrained each other. This study provided reference for sustainable development and rational exploitation of medicinal plant resources in future.

Assessment of Carbon Sequestration Capacity of E. ulmoides in Ruyang County and Its Ecological Suitability Zoning Based on Satellite Images of GF-6.

Eucommia ulmoides Oliver. (E. ulmoides) is a species of small tree native to China. It is a valuable medicinal herb that can be used to treat Alzheimer's disease, diabetes, hypertension, and other diseases. In addition, E. ulmoides is a source of rubber. It has both medicinal and ecological value. As ecological problems become increasingly prominent, accurate information on the cultivated area of E. ulmoides is important for understanding the carbon sequestration capacity and ecological suitability zoning of E. ulmoides. In previous tree mapping studies, no studies on the spectral characteristics of E. ulmoides and its remote sensing mapping have been seen. We use Ruyang County, Henan Province, China, as the study area. Firstly, using the 2021 Gao Fen-6 (GF-6) Wide Field of View (WFV) time series images covering the different growth stages of E. ulmoides based on the participation of red-edge bands, several band combination schemes were constructed. The optimal time window to identify E. ulmoides was selected by calculating the separability of E. ulmoides from other land cover types for different schemes. Secondly, a random forest algorithm based on several band combination schemes was investigated to map the E. ulmoides planting areas in Ruyang County. Thirdly, the annual NPP values of E. ulmoides were estimated using an improved Carnegie Ames Stanford Approach (CASA) to a light energy utilization model, which, in turn, was used to assess the carbon sequestration capacity. Finally, the ecologically suitable distribution zone of E. ulmoides under near current and future (2041-2060) climatic conditions was predicted using the MaxEnt model. The results showed that the participation of the red-edge band of the GF-6 data in the classification could effectively improve the recognition accuracy of E. ulmoides, making its overall accuracy reach 96.62%; the high NPP value of E. ulmoides was mainly concentrated in the south of Ruyang County, with a total annual carbon sequestration of 540.104835 t CM-2·a-1. The ecological suitability zone of E. ulmoides can be divided into four classes: unsuitable area, low suitable area, medium suitable area, and high suitable area. The method proposed in this paper applies to the real-time monitoring of E. ulmoides, highlighting its potential ecological value and providing theoretical reference and data support for the reasonable layout of E. ulmoides.

Single-molecule imaging reveals distinct elongation and frameshifting dynamics between frames of expanded RNA repeats in C9ORF72-ALS/FTD.

C9ORF72 hexanucleotide repeat expansion is the most common genetic cause of both amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). One pathogenic mechanism is the accumulation of toxic dipeptide repeat (DPR) proteins like poly-GA, GP and GR, produced by the noncanonical translation of the expanded RNA repeats. However, how different DPRs are synthesized remains elusive. Here, we use single-molecule imaging techniques to directly measure the translation dynamics of different DPRs. Besides initiation, translation elongation rates vary drastically between different frames, with GP slower than GA and GR the slowest. We directly visualize frameshift events using a two-color single-molecule translation assay. The repeat expansion enhances frameshifting, but the overall frequency is low. There is a higher chance of GR-to-GA shift than in the reversed direction. Finally, the ribosome-associated protein quality control (RQC) factors ZNF598 and Pelota modulate the translation dynamics, and the repeat RNA sequence is important for invoking the RQC pathway. This study reveals that multiple translation steps modulate the final DPR production. Understanding repeat RNA translation is critically important to decipher the DPR-mediated pathogenesis and identify potential therapeutic targets in C9ORF72-ALS/FTD.

Translation dysregulation in neurodegenerative diseases: a focus on ALS.

RNA translation is tightly controlled in eukaryotic cells to regulate gene expression and maintain proteome homeostasis. RNA binding proteins, translation factors, and cell signaling pathways all modulate the translation process. Defective translation is involved in multiple neurological diseases including amyotrophic lateral sclerosis (ALS). ALS is a progressive neurodegenerative disorder and poses a major public health challenge worldwide. Over the past few years, tremendous advances have been made in the understanding of the genetics and pathogenesis of ALS. Dysfunction of RNA metabolisms, including RNA translation, has been closely associated with ALS. Here, we first introduce the general mechanisms of translational regulation under physiological and stress conditions and review well-known examples of translation defects in neurodegenerative diseases. We then focus on ALS-linked genes and discuss the recent progress on how translation is affected by various mutant genes and the repeat expansion-mediated non-canonical translation in ALS.

RBFOX2 recognizes N6-methyladenosine to suppress transcription and block myeloid leukaemia differentiation.

N6-methyladenosine (m6A) methylation can be deposited on chromatin-associated RNAs (caRNAs) by the RNA methyltransferase complex (MTC) to regulate chromatin state and transcription. However, the mechanism by which MTC is recruited to distinct genomic loci remains elusive. Here we identify RBFOX2, a well-studied RNA-binding protein, as a chromatin factor that preferentially recognizes m6A on caRNAs. RBFOX2 can recruit RBM15, an MTC component, to facilitate methylation of promoter-associated RNAs. RBM15 also physically interacts with YTHDC1 and recruits polycomb repressive complex 2 (PRC2) to the RBFOX2-bound loci for chromatin silencing and transcription suppression. Furthermore, we found that this RBFOX2/m6A/RBM15/YTHDC1/PRC2 axis plays a critical role in myeloid leukaemia. Downregulation of RBFOX2 notably inhibits survival/proliferation of acute myeloid leukaemia cells and promotes their myeloid differentiation. RBFOX2 is also required for self-renewal of leukaemia stem/initiation cells and acute myeloid leukaemia maintenance. Our study presents a pathway of m6A MTC recruitment and m6A deposition on caRNAs, resulting in locus-selective chromatin regulation, which has potential therapeutic implications in leukaemia.

Globally reduced N6-methyladenosine (m6A) in C9ORF72-ALS/FTD dysregulates RNA metabolism and contributes to neurodegeneration.

Repeat expansion in C9ORF72 is the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Here we show that N6-methyladenosine (m6A), the most prevalent internal mRNA modification, is downregulated in C9ORF72-ALS/FTD patient-derived induced pluripotent stem cell (iPSC)-differentiated neurons and postmortem brain tissues. The global m6A hypomethylation leads to transcriptome-wide mRNA stabilization and upregulated gene expression, particularly for genes involved in synaptic activity and neuronal function. Moreover, the m6A modification in the C9ORF72 intron sequence upstream of the expanded repeats enhances RNA decay via the nuclear reader YTHDC1, and the antisense RNA repeats can also be regulated through m6A modification. The m6A reduction increases the accumulation of repeat RNAs and the encoded poly-dipeptides, contributing to disease pathogenesis. We further demonstrate that, by elevating m6A methylation, we could significantly reduce repeat RNA levels from both strands and the derived poly-dipeptides, rescue global mRNA homeostasis and improve survival of C9ORF72-ALS/FTD patient iPSC-derived neurons.

Pairwise comparative analysis of six haplotype assembly methods based on users' experience.

BACKGROUND: A haplotype is a set of DNA variants inherited together from one parent or chromosome. Haplotype information is useful for studying genetic variation and disease association. Haplotype assembly (HA) is a process of obtaining haplotypes using DNA sequencing data. Currently, there are many HA methods with their own strengths and weaknesses. This study focused on comparing six HA methods or algorithms: HapCUT2, MixSIH, PEATH, WhatsHap, SDhaP, and MAtCHap using two NA12878 datasets named hg19 and hg38. The 6 HA algorithms were run on chromosome 10 of these two datasets, each with 3 filtering levels based on sequencing depth (DP1, DP15, and DP30). Their outputs were then compared. RESULT: Run time (CPU time) was compared to assess the efficiency of 6 HA methods. HapCUT2 was the fastest HA for 6 datasets, with run time consistently under 2 min. In addition, WhatsHap was relatively fast, and its run time was 21 min or less for all 6 datasets. The other 4 HA algorithms' run time varied across different datasets and coverage levels. To assess their accuracy, pairwise comparisons were conducted for each pair of the six packages by generating their disagreement rates for both haplotype blocks and Single Nucleotide Variants (SNVs). The authors also compared them using switch distance (error), i.e., the number of positions where two chromosomes of a certain phase must be switched to match with the known haplotype. HapCUT2, PEATH, MixSIH, and MAtCHap generated output files with similar numbers of blocks and SNVs, and they had relatively similar performance. WhatsHap generated a much larger number of SNVs in the hg19 DP1 output, which caused it to have high disagreement percentages with other methods. However, for the hg38 data, WhatsHap had similar performance as the other 4 algorithms, except SDhaP. The comparison analysis showed that SDhaP had a much larger disagreement rate when it was compared with the other algorithms in all 6 datasets. CONCLUSION: The comparative analysis is important because each algorithm is different. The findings of this study provide a deeper understanding of the performance of currently available HA algorithms and useful input for other users.

Elevated nuclear TDP-43 induces constitutive exon skipping.

Cytoplasmic inclusions and loss of nuclear TDP-43 are key pathological features found in several neurodegenerative disorders, suggesting both gain- and loss-of-function mechanisms of disease. To study gain-of-function, TDP-43 overexpression has been used to generate in vitro and in vivo model systems. Our study shows that excessive levels of nuclear TDP-43 protein lead to constitutive exon skipping that is largely species-specific. Furthermore, while aberrant exon skipping is detected in some human brains, it is not correlated with disease, unlike the incorporation of cryptic exons that occurs after loss of TDP-43. Our findings emphasize the need for caution in interpreting TDP-43 overexpression data, and stress the importance of controlling for exon skipping when generating models of TDP-43 proteinopathy. Understanding the subtle aspects of TDP-43 toxicity within different subcellular locations is essential for the development of therapies targeting neurodegenerative disease.

METTL14 is a chromatin regulator independent of its RNA N6-methyladenosine methyltransferase activity.

METTL3 and METTL14 are two components that form the core heterodimer of the main RNA m6A methyltransferase complex (MTC) that installs m6A. Surprisingly, depletion of METTL3 or METTL14 displayed distinct effects on stemness maintenance of mouse embryonic stem cell (mESC). While comparable global hypo-methylation in RNA m6A was observed in Mettl3 or Mettl14 knockout mESCs, respectively. Mettl14 knockout led to a globally decreased nascent RNA synthesis, whereas Mettl3 depletion resulted in transcription upregulation, suggesting that METTL14 might possess an m6A-independent role in gene regulation. We found that METTL14 colocalizes with the repressive H3K27me3 modification. Mechanistically, METTL14, but not METTL3, binds H3K27me3 and recruits KDM6B to induce H3K27me3 demethylation independent of METTL3. Depletion of METTL14 thus led to a global increase in H3K27me3 level along with a global gene suppression. The effects of METTL14 on regulation of H3K27me3 is essential for the transition from self-renewal to differentiation of mESCs. This work reveals a regulatory mechanism on heterochromatin by METTL14 in a manner distinct from METTL3 and independently of m6A, and critically impacts transcriptional regulation, stemness maintenance, and differentiation of mESCs.

Cell-specific regulation of gene expression using splicing-dependent frameshifting.

Precise and reliable cell-specific gene delivery remains technically challenging. Here we report a splicing-based approach for controlling gene expression whereby separate translational reading frames are coupled to the inclusion or exclusion of mutated, frameshifting cell-specific alternative exons. Candidate exons are identified by analyzing thousands of publicly available RNA sequencing datasets and filtering by cell specificity, conservation, and local intron length. This method, which we denote splicing-linked expression design (SLED), can be combined in a Boolean manner with existing techniques such as minipromoters and viral capsids. SLED can use strong constitutive promoters, without sacrificing precision, by decoupling the tradeoff between promoter strength and selectivity. AAV-packaged SLED vectors can selectively deliver fluorescent reporters and calcium indicators to various neuronal subtypes in vivo. We also demonstrate gene therapy utility by creating SLED vectors that can target PRPH2 and SF3B1 mutations. The flexibility of SLED technology enables creative avenues for basic and translational research.

Main flavor compounds and molecular regulation mechanisms in fruits and vegetables.

Fruits and vegetables (F&V) are an indispensable part of a healthy diet. The volatile and nonvolatile compounds present in F&V constitute unique flavor substances. This paper reviews the main flavor substances present in F&V, as well as the biosynthetic pathways and molecular regulation mechanisms of these compounds. A series of compounds introduced include aromatic substances, soluble sugars and organic acids, which constitute the key flavor substances of F&V. Esters, phenols, alcohols, amino acids and terpenes are the main volatile aromatic substances, and nonvolatile substances are represented by amino acids, fatty acids and carbohydrates; The combination of these ingredients is the cause of the sour, sweet, bitter, astringent and spicy taste of these foods. This provides a theoretical basis for the study of the interaction between volatile and nonvolatile substances in F&V, and also provides a research direction for the healthy development of food in the future.

Thorough statistical analyses of breast cancer co-methylation patterns.

BACKGROUND: Breast cancer is one of the most commonly diagnosed cancers. It is associated with DNA methylation, an epigenetic event with a methyl group added to a cytosine paired with a guanine, i.e., a CG site. The methylation levels of different genes in a genome are correlated in certain ways that affect gene functions. This correlation pattern is known as co-methylation. It is still not clear how different genes co-methylate in the whole genome of breast cancer samples. Previous studies are conducted using relatively small datasets (Illumina 27K data). In this study, we analyze much larger datasets (Illumina 450K data). RESULTS: Our key findings are summarized below. First, normal samples have more highly correlated, or co-methylated, CG pairs than tumor samples. Both tumor and normal samples have more than 93% positive co-methylation, but normal samples have significantly more negatively correlated CG sites than tumor samples (6.6% vs. 2.8%). Second, both tumor and normal samples have about 94% of co-methylated CG pairs on different chromosomes, but normal samples have 470 million more CG pairs. Highly co-methylated pairs on the same chromosome tend to be close to each other. Third, a small proportion of CG sites' co-methylation patterns change dramatically from normal to tumor. The percentage of differentially methylated (DM) sites among them is larger than the overall DM rate. Fourth, certain CG sites are highly correlated with many CG sites. The top 100 of such super-connector CG sites in tumor and normal samples have no overlaps. Fifth, both highly changing sites and super-connector sites' locations are significantly different from the genome-wide CG sites' locations. Sixth, chromosome X co-methylation patterns are very different from other chromosomes. Finally, the network analyses of genes associated with several sets of co-methylated CG sites identified above show that tumor and normal samples have different patterns. CONCLUSIONS: Our findings will provide researchers with a new understanding of co-methylation patterns in breast cancer. Our ability to thoroughly analyze co-methylation of large datasets will allow researchers to study relationships and associations between different genes in breast cancer.

Differential Expression of Calycosin-7-O-ß-D-glucoside Biosynthesis Genes and Accumulation of Related Metabolites in Different Organs of Astragalus membranaceus Bge. var. mongholicus (Bge.) Hsiao Under Drought Stress.

Calycosin-7-O-ß-D-glycoside (CG), as a flavonoid, plays an important role in the abiotic stress response of Astragalus membranaceus Bge. var. mongholicus (Bge.) Hsiao (A. mongholicus). CG is also an active ingredient in A. mongholicus with high medicinal value. However, the response mechanism of the CG biosynthetic pathway of drought stress is not clear. In this research, drought stress was inflicted upon A. mongholicus, and the variations in flavonoid metabolites and the correlating gene expression in CG biosynthesis were studied in roots, stems, and leaves of A. mongholicus by UHPLC-MRM-MS/MS and qRT-PCR. Drought stress reduced the dry weight and increased the content of malondialdehyde (MDA) and proline. Drought was beneficial to the accumulation of L-phenylalanine and 4-coumaric acid in leaves and promoted the accumulation of all target compounds in the roots, except calycosin. Overexpression of AmIOMT was observed in the leaves, but the content of formononetin which is the product of isoflavone O-methyltransferase (IOMT) catalysis was higher in stems than in leaves. This research aims to further understand the acclimation of abiotic stress and the regulation mechanism of flavonoid accumulation in A. mongholicus.

Measuring Repeat-Associated Non-AUG (RAN) Translation.

Expansions of short nucleotide repeats account for more than 50 neurological or neuromuscular diseases. Many repeat expansion-containing RNAs can generate toxic repeat proteins through repeat-associated non-AUG (RAN) translation in all the reading frames. Understanding how RAN translation occurs and what cellular factors regulate this process will help decipher the basic mechanism of the molecular process and disease pathogenesis. Using reporter systems to quantitatively measure RAN translation provides a platform to examine candidate genes/pathways and screen for modifiers of this non-canonical pathway. In this chapter, we describe the dual-luciferase reporter system to measure RAN translation using C9ORF72 GGGGCCexp as an example, which is the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD).

Quantitatively identifying the emission sources of pharmaceutically active compounds (PhACs) in the surface water: Method development, verification and application in Huangpu River, China.

Recognizing the main sources of pharmaceutically active compounds (PhACs) found in surface waters has been a challenge to the effective control of PhAC contamination from the sources. In the present study, a novel method based on Characteristic Matrix (ChaMa) model of indicator PhACs to quantitatively identify the contribution of multiple emission sources was developed, verified, and applied in Huangpu River, Shanghai. Carbamazepine (CBZ), caffeine (CF) and sulfadiazine (SDZ) were proposed as indicators. Their occurrence patterns in the corresponding emission sources and the factor analysis of their composition in the surface water samples were employed to construct the ChaMa model and develop the source apportionment method. Samples from typical emission sources were collected and analyzed as hypothetical surface water samples, to verify the method proposed. The results showed that the calculated contribution proportions of emission sources to the corresponding source samples were 45%-85%, proving the feasibility of the method. Finally, the method was applied to different sections in Huangpu River, and the results showed that livestock wastewater was the dominant emission source, accounting for 55%-73% in the upper reach of Huangpu River. Untreated municipal wastewater was dominant in the middle and lower reaches of Huangpu River, accounting for 76%-94%. This novel source apportionment method allows the quantitative identification of the contribution of multiple PhAC emission sources. It can be replicated in other regions where the occurrence of localized indicators was available, and will be helpful to control the contamination of PhACs in the water environment from the major sources.

Nuclear export and translation of circular repeat-containing intronic RNA in C9ORF72-ALS/FTD.

C9ORF72 hexanucleotide GGGGCC repeat expansion is the most common genetic cause of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD). Repeat-containing RNA mediates toxicity through nuclear granules and dipeptide repeat (DPR) proteins produced by repeat-associated non-AUG translation. However, it remains unclear how the intron-localized repeats are exported and translated in the cytoplasm. We use single molecule imaging approach to examine the molecular identity and spatiotemporal dynamics of the repeat RNA. We demonstrate that the spliced intron with G-rich repeats is stabilized in a circular form due to defective lariat debranching. The spliced circular intron, instead of pre-mRNA, serves as the translation template. The NXF1-NXT1 pathway plays an important role in the nuclear export of the circular intron and modulates toxic DPR production. This study reveals an uncharacterized disease-causing RNA species mediated by repeat expansion and demonstrates the importance of RNA spatial localization to understand disease etiology.