DMPK 3' untranslated repeat expansions in unexplained sudden cardiac death in the young.
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Generation of isogenic rescue iPSC lines by targeted CTG-repeat excision for myotonic dystrophy type 1.
An expanded CTG repeat in the Dystrophia Myotonica Protein Kinase (DMPK) gene is associated with myotonic dystrophy type 1 (DM1), an autosomal dominant neuromuscular disorder characterised by progressive muscle weakness, myotonia, cognitive decline, and a variety of other manifestations. Here, we report the generation of isogenic induced pluripotent stem cell (iPSC) lines, derived from patient DM1 iPSC lines carrying varying expanded (CTG)n repeats in DMPK. These gene-edited isogenic iPSC lines, in which the pathogenic repeat has been excised, serve as a reference for assessing DM1-associated phenotypes in relevant differentiated cell types, such as muscle progenitor cells and neurons.
Humans↗
Dynamics and variability of transcriptomic dysregulation in congenital myotonic dystrophy during pediatric development.
Myotonic dystrophy type 1 (DM1) is a multi-systemic disorder caused by expansion of CTG microsatellite repeats within DMPK. The most severe form, congenital myotonic dystrophy (CDM), has symptom onset at birth due to large intergenerational repeat expansions. Despite a common mutation, CDM individuals present with a distinct clinical phenotype and absence of common DM1 symptoms. Given the clinical divergence, it is unknown if the hallmark of DM1 pathology, dysregulation of alternative splicing (AS) due to sequestration of MBNL proteins within toxic CUG repeat RNAs, contributes to disease throughout pediatric development. To evaluate global transcriptomic dysregulation, RNA-seq was performed on 36 CDM skeletal muscle biopsies ages 2 weeks to 16 years, including two longitudinal samples. Fifty DM1 and adult/pediatric controls were also sequenced as comparative groups. Despite a large CTG expansion and shared age of onset, CDM individuals presented with a heterogenous, MBNL-dependent mis-splicing signature. Estimation of intracellular MBNL concentrations from splicing responses of select events correlated with total spliceopathy and revealed a distinct, triphasic pattern of AS dysregulation across pediatric development. CDM infants (< 2 years) possess severe mis-splicing that significantly improves in early childhood (2-8 years) independent of sex or CTG repeat load. Adolescent individuals (8-16 years) stratified into two populations with a full range of global splicing dysregulation. DMPK expression changes correlated with alterations in splicing severity during development. This study reveals the complex dynamics of the CDM muscle transcriptome and provides insights into new therapeutic strategies, timing of therapeutic intervention, and biomarker development.
Child, Preschool↗
Mitochondrial dysfunction in the pathogenesis of intervertebral disc herniation: a mitochondrial related genome-wide Mendelian randomization analysis.
BACKGROUND: As a degenerative disease, the pathophysiology of intervertebral disc herniation (IDH) closely related to mitochondrial dysfunction. However, the specific molecular mechanisms involved have yet to be precisely established. METHODS: Here, we employed a two-sample, two-step Mendelian Randomization (MR) approach, along with summary-Data-Based MR, genetic colocalization, full phenomenon association analysis, and GO and KEGG enrichment analysis to investigate the genetical effects of mitochondrial dysfunction on IDH. RESULTS: From the intercross between mitochondrial-related genes and eQTLGen genes, we obtained seven genes (DMPK, EHHADH, SLC25A16, ME3, METTL17, TUFM, NDUFA13) with strong causal association with disc herniation. By SMR and genetic colocalization analysis, we further identify five key genes (EHHADH, METTL17, TUFM, NDUFA13, DMPK) as the direct causal tartgeted genes with no heterogeneity and pleiotropy in the SNPs of the genes. Full phenomenon Mendelian randomization was performed to determine possible side effects of the 5 targeting genes. Finally, we validated the expressions of key genes in the degenerative intervertebral discs tissues by qRT-PCR and double-immunofluorescence examinations, and the results were consistent with the MR analysis. CONCLUSIONS: Our study provided genetic support for the relationship between mitochondrial related genes and IDH, implicating potential therapeutic targets for future development. However, more basic experiments need to be finished to validate the role of key genes in the development of IDH.
Intervertebral Disc Displacement↗
Genome-wide DNA methylation and transcriptome sequencing analyses of lens tissue in an age-related mouse cataract model.
DNA methylation is known to be associated with cataracts. In this study, we used a mouse model and performed DNA methylation and transcriptome sequencing analyses to find epigenetic indicators for age-related cataracts (ARC). Anterior lens capsule membrane tissues from young and aged mice were analyzed by MethylRAD-seq to detect the genome-wide methylation of extracted DNA. The young and aged mice had 76,524 and 15,608 differentially methylated CCGG and CCWGG sites, respectively. The Pearson correlation analysis detected 109 and 33 differentially expressed genes (DEGs) with negative methylation at CCGG and CCWGG sites, respectively, in their promoter regions. Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) functional enrichment analyses showed that DEGs with abnormal methylation at CCGG sites were primarily associated with protein kinase C signaling (Akap12, Capzb), protein threonine kinase activity (Dmpk, Mapkapk3), and calcium signaling pathway (Slc25a4, Cacna1f), whereas DEGs with abnormal methylation at CCWGG sites were associated with ribosomal protein S6 kinase activity (Rps6ka3). These genes were validated by pyrosequencing methylation analysis. The results showed that the ARC group (aged mice) had lower Dmpk and Slc25a4 methylation levels and a higher Rps6ka3 methylation than the control group (young mice), which is consistent with the results of the joint analysis of differentially methylated and differentially expressed genes. In conclusion, we confirmed the genome-wide DNA methylation pattern and gene expression profile of ARC based on the mouse cataract model with aged mice. The identified methylation molecular markers have great potential for application in the future diagnosis and treatment of ARC.
Animals↗
Microbial diversity and metabolic pathways linked to benzene degradation in petrochemical-polluted groundwater.
The rapid advance in shotgun metagenome sequencing has enabled us to identify uncultivated functional microorganisms in polluted environments. While aerobic petrochemical-degrading pathways have been extensively studied, the anaerobic mechanisms remain less explored. Here, we conducted a study at a petrochemical-polluted groundwater site in Henan Province, Central China. A total of twelve groundwater monitoring wells were installed to collect groundwater samples. Benzene appeared to be the predominant pollutant, detected in 10 out of 12 samples, with concentrations ranging from 1.4 μg/L to 5,280 μg/L. Due to the low aquifer permeability, pollutant migration occurred slowly, resulting in relatively low benzene concentrations downstream within the heavily polluted area. Deep metagenome sequencing revealed Proteobacteria as the dominant phylum, accounting for over 63 % of total abundances. Microbial α-diversity was low in heavily polluted samples, with community compositions substantially differing from those in lightly polluted samples. dmpK encoding the phenol/toluene 2-monooxygenase was detected across all samples, while the dioxygenase bedC1 was not detected, suggesting that aerobic benzene degradation might occur through monooxygenation. Sequence assembly and binning yielded 350 high-quality metagenome-assembled genomes (MAGs), with 30 MAGs harboring functional genes associated with aerobic or anaerobic benzene degradation. About 80 % of MAGs harboring functional genes associated with anaerobic benzene degradation remained taxonomically unclassified at the genus level, suggesting that our current database coverage of anaerobic benzene-degrading microorganisms is very limited. Furthermore, two genes integral to anaerobic benzene metabolism, i.e, benzoyl-CoA reductase (bamB) and glutaryl-CoA dehydrogenase (acd), were not annotated by metagenome functional analyses but were identified within the MAGs, signifying the importance of integrating both contig-based and MAG-based approaches. Together, our efforts of functional annotation and metagenome binning generate a robust blueprint of microbial functional potentials in petrochemical-polluted groundwater, which is crucial for designing proficient bioremediation strategies.
Groundwater↗
A genome-wide approach for the discovery of novel repeat expansion disorders in the Undiagnosed Diseases Network cohort.
PURPOSE: The Undiagnosed Diseases Network is a National Institutes of Health funded research study that aims to solve a broad clinical spectrum of challenging rare disease cases. Participants receive care from multiple clinical specialists, who collaborate to perform deep phenotyping and state-of-the-art multiomics analyses. As bioinformatics of short-read sequencing has matured, the discovery of repeat expansion disorders (REDs) is accelerating. REDs comprise approximately 60 characterized disorders, which exhibit a broad spectrum of phenotypes. Thus, a largely unbiased genome-wide approach in a phenotypically diverse sample will add to the diagnostic depth, explore the limits of short-read genome analysis, and establish novel candidate RED loci. METHODS: Here, we present a genome-wide analysis of repeat expansions conducted on 1018 genomes from the Undiagnosed Diseases Network. By leveraging 2 distinct bioinformatics tools, ExpansionHunter Denovo and STRling, we showed that repeat expansions can be accurately detected in short-read genomes. RESULTS: We demonstrated that a genotype-first approach can diagnose atypical cases of known REDs and provide valuable clinical insights. We present clinical details on participants with expansions in ATXN7, DMPK, FMR1, GLS, HTT, RFC1, AFF3, and MARCH6. Importantly, we highlight 2 cases of juvenile Huntington disease that were discovered through our analysis. Finally, we present a list of novel candidate short tandem repeats (TR) that could potentially be pathogenic if expanded. CONCLUSION: Importantly, our approach showcases the bioinformatic advancements in genome analysis for RED detection and highlights its practical applications.
Humans↗
Pentatricopeptide repeat protein targeting CUG repeat RNA ameliorates RNA toxicity in a myotonic dystrophy type 1 mouse model.
Myotonic dystrophy type 1 (DM1) is an autosomal dominant multisystemic disorder caused by the expansion of a CTG-triplet repeat in the 3' untranslated region of the dystrophia myotonica protein kinase (DMPK) gene. It results in the transcription of toxic RNAs that contain expanded CUG repeats (CUGexp). Splicing factors, such as muscleblind-like 1 (MBNL1), are sequestered by CUGexp, thereby disrupting the normal splicing program that is essential for various cellular functions. Pentatricopeptide repeat (PPR) proteins, originally found in plants, regulate RNA in organelles by binding in a sequence-specific manner. Here, we designed PPR proteins that specifically bind to the hexamer of CUG repeat RNAs (CUG-PPRs) and showed that CUG-PPR1 could ameliorate RNA toxicity induced by CUGexp in cell models of DM1. A single systemic recombinant adeno-associated virus (AAV9) vector-mediated gene delivery of CUG-PPR1 demonstrated long-term therapeutic effects on myotonia and restored splicing activity in a mouse model of DM1. These results highlight the potential of PPR molecules to target pathogenic RNA sequences in DM1 and potentially other RNA-mediated disorders.
Animals↗
Progressive cardiac phenotypes and reduced reversibility from long-term CUGexp RNA expression in a DM1 mouse model.
Myotonic dystrophy type 1 (DM1) is caused by an expanded CTG repeat in the DMPK gene, resulting in mutant transcripts that form expanded CUG (CUGexp) RNA foci and sequester muscleblind-like (MBNL) RNA-binding proteins. DM1 is multisystemic, with progressive worsening of disease manifestations in affected tissues. Disease progression is attributed to somatic expansion of the CTG repeats with age, resulting in production of CUGexp RNA with enhanced intrinsic toxicity due to increased MBNL sequestration. To determine the degree to which cardiac disease progression can occur independently of repeat expansion, we used a transgenic DM1 mouse model with inducible heart-specific expression of a stable, interrupted 960-CUG-repeat RNA. Sustained CUGexp RNA expression caused progressive cardiac enlargement, contractile dysfunction, conduction delay, myocardial fibrosis, and reduced survival, while MBNL-dependent splicing defects remained static, consistent with the stable repeat length. We also determined the degree of reversibility after different periods of CUGexp RNA expression by shutting off the repeat-containing transgene. Suppression of CUGexp RNA expression rescued cardiac abnormalities, but reversibility declined with longer exposure to the toxic RNA. These findings demonstrate that prolonged expression of stable CUGexp RNA drives progressive cardiac pathology, revealing a mechanism of disease progression in DM1 in addition to somatic expansion.
Animals↗