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PubMed2024

Design and evaluation of antisense sequence length for modified mouse U7 small nuclear RNA to induce efficient pre-messenger RNA splicing modulation in vitro.

Pre-messenger RNA (pre-mRNA) splicing modulation is an attractive approach for investigating the mechanisms of genetic disorders caused by mis-splicing. Previous reports have indicated that a modified U7 small nuclear RNA (U7 snRNA) is a prospective tool for modulating splicing both in vitro and in vivo. To date, very few studies have investigated the role of antisense sequence length in modified U7 snRNA. In this study, we designed a series of antisense sequences with various lengths and evaluated their efficiency in inducing splicing modulation. To express modified U7 snRNAs, we constructed a series of plasmid DNA sequences which codes cytomegalovirus (CMV) enhancer, human U1 promoter, and modified mouse U7 snRNAs with antisense sequences of different lengths. We evaluated in vitro splicing modulation efficiency using a luciferase reporter system for simple and precise evaluation as well as reverse transcription-polymerase chain reaction to monitor splicing patterns. Our in vitro assay findings suggest that antisense sequences of modified mouse U7 snRNAs have an optimal length for efficient splicing modulation, which depends on the target exon. In addition, antisense sequences that were either too long or too short decreased splicing modulation efficiency. To confirm reproducibility, we performed an in vitro assay using two target genes, mouse Fas and mouse Dmd. Together, our data suggests that the antisense sequence length should be optimized for modified mouse U7 snRNAs to induce efficient splicing modulation.

RNA, Small Nuclear↗

PubMed2026

An IRAK1-snRNA axis activates ATM to promote accurate repair within transcriptionally active chromatin.

Genomic integrity in transcriptionally active regions is pivotal for suppressing oncogenic mutations, yet the mechanisms that govern precise homologous recombination (HR) repair within these regions remain elusive. Here, we report that the IRAK1-spliceosome axis operates with small nuclear RNA (snRNA) as a central hub, potently promoting accurate repair at DNA double-strand break (DSB) sites within active chromatin in human cancer cells. Mechanistically, IRAK1 phosphorylates spliceosomal serine/arginine (SR)-rich proteins to recruit snRNA to DSBs, inducing robust condensation of the MRE11-RAD50-NBS1 (MRN) complex near transcriptionally active regions to create an ATM activation platform. Collectively, our findings define a prevalent mechanism governing region-specific precise repair in transcriptionally active domains, where snRNA acts as a "transcription repair bridge" to link transcriptional processes to HR repair and ultimately preserves genomic stability. Inhibiting IRAK1 axis impairs HR repair in transcriptionally active regions, causing a marked increase in mutation rates specific to these regions and cancer-cell chemosensitivity.

Humans↗

PubMed2025

Quantitative Real-Time PCR for Circular RNA Detection and Analysis.

In eukaryotes, nearly 2% of the genome represented by the coding proteins. However, emerging evidence suggest more than 75% of the human genome referred to as noncoding part also plays a crucial role in governing major regulatory pathways. Noncoding RNAs can be categorized into several groups, such as microRNAs (miRNAs), small nuclear RNA (snRNAs), small nucleolar RNA (snoRNAs), transfer RNA (tRNA), and circular RNA (circRNAs), which contribute to this regulatory landscape. Circular RNAs (circRNAs) are identified as a new class of regulatory noncoding RNAs with gene regulatory roles by acting as miRNA or RNA binding protein sponges or interacting with proteins. Researchers employ quantitative real-time PCR methods to examine circular RNA expression utilizing divergent primers for identification and quantification.

RNA, Circular↗

PubMed2026

The minor spliceosome component U4atac regulates JAK/STAT signaling to modulate hematopoiesis and immune responses in Drosophila melanogaster.

The small nuclear RNA U4atac is a core component of the minor spliceosome. In humans, homozygous or compound heterozygous point mutations in U4atac cause rare developmental disorders, such as Roifman syndrome, characterized by growth restriction, brain anomalies, and immune deficiency. To better define the pathophysiological role of U4atac mutations, we here establish a model of minor spliceosome dysfunction by generating a Drosophila melanogaster CRISPR/Cas9-induced U4atac mutant in the highly conserved stem II region. U4atac homozygous mutants exhibit growth and neurodevelopmental defects, immunodeficiency, and gastrointestinal symptoms. Using bulk RNA-sequencing and functional assays, we reveal that mutations in U4atac affect the splicing of a large set of transcripts involved in innate immunity, hematopoiesis, and intestinal cell functions, including the Drosophila Janus kinase (JAK) homolog hopscotch (hop). Importantly, U4atac deficiency reduces Hop expression and causes Hop-related hematopoietic defects at the embryonic and larval stages. Notably, we also observe reduced expression of Jak1 and attenuated activation of downstream signaling in patients with Roifman syndrome. Thus, our work identifies alterations of Jak signaling as part of the pathogenesis of RNU4atac-opathy.

Animals↗

PubMed2026

Prominent Movement Disorders in RNU2-2-Related Spliceosomopathy.

Pediatric movement disorders often overlap with neurodevelopmental diseases, suggesting shared molecular mechanisms. Variants in small nuclear RNA (snRNA) genes encoding spliceosome components have recently been associated with neurodevelopmental disorders, termed "RNUopathies." We analyzed genome sequencing data from 14 patients with undiagnosed pediatric movement disorders for pathogenic variants in snRNA genes. We identified recurrent de novo RNU2-2 variants (n.35A > G and n.4G > A) in two patients with intellectual disability, epilepsy, and hyperkinetic movement disorders. RNA sequencing of fibroblasts in one patient showed no characteristic transcriptomic signature. Spliceosomopathies should be considered in neurodevelopmental disorders and developmental and epileptic encephalopathies with hyperkinetic features.

Humans↗

PubMed2026

A muskrat tissue atlas of small non-coding RNAs and their regulatory roles in muskrat musk secretion.

Muskrat musk, secreted by the male muskrat scent gland during the secretion period, is a valuable natural product with promising pharmacological activities. Its synthesis is regulated not only by coding genes but also by small non-coding RNAs (sncRNAs). However, a comprehensive tissue atlas of sncRNAs in muskrats has been lacking. To address this issue, we systematically profiled the expression levels of 6 sncRNA categories (piRNA [PIWI-interacting RNA], miRNA [microRNA], snoRNA [small nucleolar RNA], snRNA [small nuclear RNA], tRNA [transfer RNA], and other RNAs) across 13 tissues of the muskrat via deep sequencing. We identified 23,957 sncRNAs (∼ 65%) exhibiting tissue-specific expression patterns throughout the body. The results show that miRNA is the main contributor to tissue specificity. Eleven tissues showed a significantly higher number of miRNA-5p arm expressions compared to the 3p arm, although the brain was an exception. Quantitative results imply that miR-477-3p/5p and miR-794-3p are potentially involved in the regulation of muskrat musk synthesis and secretion in the muskrat scent glands. Their target genes were enriched in pathways related to energy supply, lipid metabolism, and cyclic morphological changes of the scent gland. Furthermore, we constructed a set of co-expressed miRNAs based on the hormone-dominated "brain-testis-scent gland" axis and the energy metabolism-dominated "brain-liver-scent gland" axis. These results provide the most comprehensive description to date of tissue-specific and ubiquitous sncRNAs in individual muskrat tissues. We anticipate that these data will enhance the understanding of the molecular regulation underlying muskrat musk synthesis and secretion.

Animals↗

PubMed2025

A Glimpse of Noncoding RNAs: Secondary Structure, Emerging Trends, and Potential Applications in Human Diseases.

An appealing strategy for the treatment of several diseases is the therapeutic targeting of noncoding RNAs (ncRNAs), such as microRNAs (miRNAs) and long noncoding RNAs (lncRNAs). Many antisense oligonucleotides and small interfering RNAs have been tested in clinical studies over the past 10 years, and several of these have received FDA approval. However, trial results have thus far been mixed, with some studies reporting strong effects and others showing low effectiveness or side effects, including toxicity. Clinical trials for alternative entities like antimiRNAs are underway, and interest in lncRNA-based therapies is constantly growing. From this perspective, we discuss the basic overview of ncRNAs, their significant role as therapeutic biomarkers against different diseases, and the role of secondary structure in noncoding RNAs.

Humans↗

PubMed2012

MRI roadmap-guided transendocardial delivery of exon-skipping recombinant adeno-associated virus restores dystrophin expression in a canine model of Duchenne muscular dystrophy.

Duchenne muscular dystrophy (DMD) cardiomyopathy patients currently have no therapeutic options. We evaluated catheter-based transendocardial delivery of a recombinant adeno-associated virus (rAAV) expressing a small nuclear U7 RNA (U7smOPT) complementary to specific cis-acting splicing signals. Eliminating specific exons restores the open reading frame resulting in translation of truncated dystrophin protein. To test this approach in a clinically relevant DMD model, golden retriever muscular dystrophy (GRMD) dogs received serotype 6 rAAV-U7smOPT via the intracoronary or transendocardial route. Transendocardial injections were administered with an injection-tipped catheter and fluoroscopic guidance using X-ray fused with magnetic resonance imaging (XFM) roadmaps. Three months after treatment, tissues were analyzed for DNA, RNA, dystrophin protein, and histology. Whereas intracoronary delivery did not result in effective transduction, transendocardial injections, XFM guidance, enabled 30±10 non-overlapping injections per animal. Vector DNA was detectable in all samples tested and ranged from <1 to >3000 vector genome copies per cell. RNA analysis, western blot analysis, and immunohistology demonstrated extensive expression of skipped RNA and dystrophin protein in the treated myocardium. Left ventricular function remained unchanged over a 3-month follow-up. These results demonstrated that effective transendocardial delivery of rAAV-U7smOPT was achieved using XFM. This approach restores an open reading frame for dystrophin in affected dogs and has potential clinical utility.

Animals↗

PubMed2026

De Novo 2.2 Mb 19q13.42-q13.43 Microdeletion Encompassing U2AF2: Support for a Haploinsufficiency Model.

U2 small nuclear RNA auxiliary factor 2 (U2AF2) is an essential pre-mRNA splicing factor involved in the early stages of pre-mRNA splicing. To date, multiple individuals have been reported with predominantly heterozygous missense variants presenting intellectual disability, speech and motor delays, seizures, hypotonia, and thin or hypoplastic corpus callosum. Here, we describe a patient with a de novo 2.2 Mb interstitial deletion involving chromosome 19q13.42-q13.43, encompassing U2AF2, presenting with intellectual disability, epilepsy, corpus callosum hypoplasia, dysmorphic features, and congenital heart disease. The patient's clinical features overlap substantially with those reported in individuals harboring heterozygous U2AF2 variants, supporting haploinsufficiency as a plausible disease mechanism. To our knowledge, this represents the first postnatal report of complete U2AF2 gene deletion. In addition, this is the first detailed phenotypic characterization of a distal 19q chromosomal interstitial deletion, further delineating the clinical spectrum associated with this genomic region.

Humans↗

PubMed2011

Long-term restoration of cardiac dystrophin expression in golden retriever muscular dystrophy following rAAV6-mediated exon skipping.

Although restoration of dystrophin expression via exon skipping in both cardiac and skeletal muscle has been successfully demonstrated in the mdx mouse, restoration of cardiac dystrophin expression in large animal models of Duchenne muscular dystrophy (DMD) has proven to be a challenge. In large animals, investigators have focused on using intravenous injection of antisense oligonucleotides (AO) to mediate exon skipping. In this study, we sought to optimize restoration of cardiac dystrophin expression in the golden retriever muscular dystrophy (GRMD) model using percutaneous transendocardial delivery of recombinant AAV6 (rAAV6) to deliver a modified U7 small nuclear RNA (snRNA) carrying antisense sequence to target the exon splicing enhancers of exons 6 and 8 and correct the disrupted reading frame. We demonstrate restoration of cardiac dystrophin expression at 13 months confirmed by reverse transcription-PCR (RT-PCR) and immunoblot as well as membrane localization by immunohistochemistry. This was accompanied by improved cardiac function as assessed by cardiac magnetic resonance imaging (MRI). Percutaneous transendocardial delivery of rAAV6 expressing a modified U7 exon skipping construct is a safe, effective method for restoration of dystrophin expression and improvement of cardiac function in the GRMD canine and may be easily translatable to human DMD patients.

Alternative Splicing↗

PubMed2025

Biallelic variants in RNU2-2 cause the most prevalent known recessive neurodevelopmental disorder.

We recently showed that mutations in RNU4-2 and RNU2-2, two genes that are transcribed into small nuclear RNA (snRNA) components of the major spliceosome, are prevalent causes of dominant neurodevelopmental disorders (NDDs). By genetic association comparing 12,776 NDD cases with 56,064 controls, we now demonstrate the existence of a recessive form of RNU2-2 syndrome that, in England, is even more common than the dominant form. We inferred log Bayes factors for dominant and recessive models of association of 14.0 and 18.2, respectively, and observed 17 rare variants with a posterior probability of pathogenicity conditional on recessive association >0.8. This conservative threshold identified 18 probands (all with unaffected parents) and five affected siblings, each carrying two alleles in trans at these variants. A relaxed threshold of >0.6 identified a further 13 candidate probands. We estimate that recessive RNU2-2 syndrome accounts for 7-10% of families with a diagnosed recessive NDD, and is 36-62% as prevalent as the dominant RNU4-2-related disorder ReNU syndrome. We identified a further seven cases in five pedigrees in two replication collections. Cases are characterized by intellectual disability, global developmental delay and seizures. The variants are predicted to destabilize stem loops and binding domains of the U2-2 snRNA that contribute to spliceosome quaternary structure, intron recognition and catalytic function. Despite this, whole-blood derived RNA-seq data from three patients did not reveal splicing defects, in line with previous analogous observations for dominant RNU2-2 syndrome.

Journal Article↗

PubMed2025

Systematic analysis of snRNA genes reveals frequent RNU2-2 variants in dominant and recessive developmental and epileptic encephalopathies.

Variants in spliceosomal small nuclear RNA (snRNA) genes RNU4-2 (ReNU syndrome), RNU5B-1, and RNU2-2 have recently been linked to dominant neurodevelopmental disorders (NDDs), revealing a major, previously overlooked role for noncoding snRNAs in human disease. Here, we systematically analysed 200 potentially functional snRNA genes in a French cohort comprising 26,911 individuals with rare disorders and through international collaborations. We identify de novo and biallelic variants in RNU2-2 associated with both dominant and recessive NDDs in 126 individuals from 108 unrelated families. Recessive RNU2-2 NDD is at least twice as frequent as the dominant NDD caused by n.4G>A and n.35A>G, and often arises from a de novo variant in trans with an inherited allele, reflecting the high mutability of snRNA genes. Dominant and recessive RNU2-2-NDDs share overlapping clinical features with frequent epilepsy. Blood transcriptomics and DNA methylation analyses revealed subtle, variant-specific effects on splicing and episignatures. Our findings support a gradient-of-impact model and a continuum between dominant and recessive inheritance, establishing RNU2-2 variants as a frequent cause of NDDs, nearly as prevalent as ReNU syndrome.

Journal Article↗

PubMed2025

Proteins that recognize unique features of U7 snRNA and may substitute for Gemin5 in the assembly of U7-specific Sm ring.

U7 snRNA is a 60 nucleotide component of U7 snRNP, a multisubunit endonuclease that cleaves precursors of metazoan replication-dependent histone mRNAs at the 3' end, hence generating mature histone mRNAs. The Sm site in U7 snRNA differs from the Sm site in spliceosomal snRNAs and promotes the assembly of a unique Sm ring containing Lsm10 and Lsm11 instead of the spliceosomal SmD1 and SmD2 proteins. While the spliceosomal-type Sm site is recognized by Gemin5, a subunit of the SMN complex, the identity of the protein that recognizes the unusual Sm site of U7 snRNA resulting in the incorporation of Lsm10 and Lsm11 has not been determined. Here, we looked for proteins in mammalian extracts that interact with U7 snRNA and identified polypyrimidine tract-binding protein 1 (PTBP1) and insulin-like growth factor 2 mRNA-binding protein 3 (IGF2BP3) as two major proteins with this characteristic. The binding of PTBP1 and IGF2BP3 to U7 snRNA depends on its unique Sm site and on the upstream CUCUUU motif that base-pairs with histone pre-mRNAs and defines substrate specificity of U7 snRNP. Among proteins that bind U7 snRNA, we also identified hnRNP A1. We show that hnRNP A1 interacts with the SMN protein of the SMN complex, a likely prerequisite for the protein that substitutes for Gemin5 in the assembly of U7-specific Sm ring. Our results also suggest a mechanism that explains why Gemin5 does not bind the Sm site of U7 snRNA.

RNA, Small Nuclear↗

PubMed2025

Decoding ALS from the tail end of RNA.

In this issue of Cell Genomics, McKeever et al.1 generate a single-nucleus transcriptomic atlas of ALS/FTLD brain and reveal widespread alternative polyadenylation changes. Their findings highlight 3' end RNA processing as a central integrator of stress responses, cell-type specificity, and disease susceptibility, offering new mechanistic insight and potential therapeutic directions.

Cell Nucleus↗

PubMed2025

Rescue of common and rare exon 2 skipping variants of the GAA gene using modified U1 snRNA.

BACKGROUND: Pompe disease (PD) is an autosomal recessive lysosomal storage disorder caused by the deficient activity of acid alpha glucosidase (GAA) enzyme due to mutations in the GAA gene. As a result, undigested glycogen accumulates within lysosomes causing their dysfunction. From a clinical point of view, the disease can be classified in infantile-onset (IO) and late-onset (LO) forms. The common GAA c.-32-13T>G variant, found in 40-70% of LO-PD alleles, is a leaky splicing mutation interfering with the correct GAA exon 2 recognition by the spliceosome leading to the production of non-functional GAA transcripts. In this study, we used modified, GAA-tailored U1 snRNAs to correct the aberrant splicing determined by the c.-32-13T>G and other GAA exon 2-skipping mutations. METHODS: A set of constructs expressing 5 different engineered U1 snRNAs was generated. A functional splicing assay using a GAA hybrid minigene carrying different variants known to affect GAA exon 2 splicing was used to test the effect of engineered U1 snRNAs on exon 2 inclusion. The effect on endogenously expressed GAA transcript and GAA enzymatic activity was assessed by transfecting patient-derived fibroblasts bearing the common c.-32-13T>G with the best performing modified U1 snRNA. RESULTS: Modified U1-3, U1+1 and U1+6 snRNAs were all able to increase, in a dose-dependent manner, the inclusion of exon 2 within the transcript derived from the GAA minigene harbouring the c.-32-13T>G variant. The U1+1 was the most effective one (2,5 fold increase). Moreover, U1+1 snRNA partially rescued the correct splicing of GAA minigenes harbouring mutations that affect the 3'ss (c.-32-3C>G, c.-32-2A>G) and the 5'ss (c.546G>A, c.546G>C, c.546G>T). Notably, the treatment of patient-derived fibroblasts carrying the c.-32-13T>G mutation with the U1+1 snRNA increased the amount of normal GAA mRNA by 1,8 fold and the GAA enzymatic activity by 70%. CONCLUSIONS: we provide the proof-of-concept for the use of modified GAA-tailored U1 snRNAs, designed to potentiate the recognition of the GAA exon 2 5'ss, as therapeutic tools to correct the aberrant transcripts carrying variants that affect exon 2 splicing, including the common c.-32-13T>G variant.

Humans↗

PubMed2025

Rescue of a panel of Hemophilia A-causing 5'ss splicing mutations by unique Exon-specific U1snRNA variants.

BACKGROUND: Aberrant mRNA splicing is a well-established pathogenic mechanism for human disease, but its real impact is hardly predictable and underestimated. Splicing can be therefore modulated for therapeutic purposes, and splicing-switching molecules are in clinics for some diseases. Here, conscious that over 10% of all pathogenic mutations occurs at 5'ss, we aimed at characterizing and rescuing nine 5'ss mutations in three models of defective F8 exons whose skipping would lead to factor VIII (FVIII) deficiency (Hemophilia A), the most frequent coagulation factor disorder. METHODS: HEK293T cells were transfected with F8 minigene variants, alone or with engineered U1 small nuclear RNAs (U1snRNAs), and splicing patterns analysed via RT-PCR. RESULTS: All 5'ss mutations induced exon skipping, and the proportion of correct transcripts, not predictable by computational analysis, was consistent with residual FVIII levels in patients. For each exon we identified a unique engineered U1snRNAs, either compensatory or Exon Specific (ExSpeU1), able to rescue all mutations. Overall, ExSpeU1s were more effective than compensatory U1snRNAs, particularly in the defective exons 6 and 22. CONCLUSIONS: Data highlight the importance of splicing assays to elucidate genotype-phenotype relationships and proved the correction efficacy of ExSpeU1s for each targeted defective F8 exon, thus expanding their translational potential for HA.

Humans↗

PubMed2026

Phenotypic and transcriptomic characterization of biallelic RNU2-2 developmental and epileptic encephalopathy.

OBJECTIVE: A significant proportion of individuals with suspected genetic developmental and epileptic encephalopathies (DEEs) remain unsolved following whole genome sequencing (WGS). Here we describe biallelic RNU2-2 variants causing a recently reported, severe, recessive DEE. METHODS: We screened individuals who have received WGS analyses at the Genomic Medicine Centre Karolinska for Rare Diseases for biallelic RNU2-2 variants. Deep phenotyping was performed through reviewing entire medical histories and phenotypic traits were transcribed to their corresponding Human Phenotype Ontology (HPO) term. HPO terms were used to generate pairwise phenotypic similarity scores and assess for significantly shared phenotype enrichment in the RNU2-2 sub-cohort. RNA sequencing analyses were performed in fibroblast and blood tissues to compare splicing events between RNU2-2 individuals and two independent control groups. RESULTS: We identified 14 individuals from nine families with 12 ultra-rare biallelic RNU2-2 variants clustering in the conserved 5' domains. Genotype data from 13 of 14 individuals has been reported previously as part of a larger cohort. All individuals presented with a highly concordant, severe DEE, characterized by severe to profound intellectual disability, inability to walk or communicate, hyperkinesia, and refractory seizures. Infantile spasms and tonic seizures were the predominant seizure types and a Lennox-Gastaut syndrome-like phenotype was common. These individuals had a significantly similar phenotypic signature when compared with 703 individuals with complex pediatric epilepsies (two-sided Monte Carlo permutation test, p = .005). RNA sequencing analyses showed aberrant splicing, with the most pronounced effects in fibroblast tissues in mutually exclusive exon and alternate 3' splice-site events, which were not detectable in blood. SIGNIFICANCE: We present deep phenotyping data and transcriptomic analyses that provide support for rare, 5' clustering biallelic RNU2-2 variants causing this novel, severe DEE. We propose an RNA sequencing methodology on fibroblast tissue for future validation of RNU2-2 variants.

autosomal recessive disease↗

PubMed2026

Prenatal Phenotypic Features of Five Fetal Cases With RNU4ATAC-Associated Microcephalic Osteodysplastic Primordial Dwarfism Type I.

OBJECTIVE: To present the prenatal sonographic features, genomic findings, and pregnancy outcomes of fetuses with biallelic pathogenic RNU4ATAC variants linked to microcephalic osteodysplastic primordial dwarfism type I (MOPD1). METHODS: This retrospective case series includes five prenatal cases with MOPD1. Diagnoses were established by prenatal ultrasound and genetic testing. Genome sequencing (GS) or targeted exome sequencing (ES) detected the variants either prenatally or after termination of pregnancy (TOP). Clinical data including parental demographics, ultrasound findings, and pregnancy outcomes were collected. RESULTS: All fetuses presented with consistent anomalies on ultrasound including intrauterine growth restriction (IUGR), microcephaly, agenesis of the corpus callosum (ACC), intracranial cysts, lissencephaly, and micrognathia. IUGR was the earliest anomaly detected in all five cases. Prenatal ultrasound findings suggestive of skeletal dysplasia were identified in one case. All cases carried biallelic pathogenic RNU4ATAC variants associated with MOPD1. TOP was chosen in four cases. One fetus was delivered at 39 + 1 weeks with genetic diagnosis confirmed at 27 weeks. CONCLUSION: IUGR, microcephaly and ACC can be detected in fetuses with MOPD1 at around 18 weeks of gestation. Interestingly, skeletal dysplasia was not a consistent prenatal finding. Variants in the non-coding RNU4ATAC gene need to be detected by GS or targeted approaches beyond standard ES.

Humans↗