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PubMed2026

RNA splicing and cardiovascular disease: a guide for cardiologists.

Alternative splicing (AS) is a fundamental RNA processing mechanism, which generates different RNA transcripts and consequently different protein isoforms from a single gene. This increases the diversity of proteins within an organism and can fine-tune biological processes. This review examines how cardiac-enriched RNA-binding proteins establish heart-specific splicing programs governing aspects of cardiac development, function, and disease. Developmentally, coordinated sarcomeric isoform switches underpin the foetal-to-adult transition and further isoform rewiring in ion channel and kinase genes determine electrophysiology and excitation-contraction coupling. AS contributes to the pathogenesis of several cardiomyopathies and emerging datasets suggest that pathological hypertrophy engages distinct splicing signatures compared with physiological hypertrophy. This review summarizes diagnostic and prognostic opportunities arising from bulk, long-read, and single-cell/nucleus transcriptomics, which resolve cell type-specific isoforms and disease-associated switches. Circulating RNA biomarkers (including splice ratios and circularRNAs) may signify myocardial remodelling and arrhythmic risk. Integrative approaches that link AS with proteomics and genomics improve variant interpretation, reveal previously unannotated protein isoforms, and enable tracking of disease progression and therapy response. Finally, an outline of therapeutic strategies to modulate AS in cardiovascular disease (CVD), including antisense oligonucleotides, small molecules, and genome-editing modalities (CRISPR, base, and prime editing), is provided. The major challenges that remain before splice-targeting therapeutics can be targeted to treat cardiovascular disease are highlighted. Lessons from neuromuscular indications establish clinical feasibility of splicing correction and motivate translation to cardiology. Together, mechanistic insight, biomarker development, and therapeutic innovation position RNA splicing as a tractable axis for precision cardiovascular medicine.

Humans↗

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↗

PubMed2025

Increased yield of genetic diagnoses in inherited heart diseases using expanded genome and RNA-splicing analyses.

PURPOSE: The Australian Genomics Cardiovascular Disorders Flagship investigated genome sequencing as a first-line genetic test in 600 individuals with cardiomyopathy, primary arrhythmia syndromes, or congenital heart disease. Analysis of disease-specific virtual gene panels achieved a genetic diagnosis in 38% of participants. We sought to increase genetic diagnosis yields by analyzing lesser-evidenced disease genes, the mitochondrial genome, and by functional analysis of predicted splice-altering variants. METHODS: Genome sequences of 520 participants with cardiomyopathy or primary arrhythmia syndromes were reanalyzed in 572 cardiac genes and the mitochondrial genome. Participants with congenital heart disease were excluded. Variants predicted in silico to disrupt splicing were assessed with blood RNA and minigenes. RESULTS: A new genetic diagnosis was achieved in 4% (19/520) of participants, including deep intronic and mitochondrial genome variants. Ten participants had diagnostic variants in lesser evidenced disease genes; 9 had splicing variant pathogenicity functionally validated. Eleven participants had a newly identified variant of uncertain significance with high suspicion of pathogenicity, warranting clinical review. Our data supported the gene-disease association of 1 new cardiomyopathy gene, TBX20. CONCLUSION: Identifying new gene-disease relationships, maintaining contemporary gene panels, and integrating functional studies to refine splicing variant classifications increase genetic diagnoses for cardiomyopathies and primary arrhythmia syndromes.

Humans↗

PubMed2026

SpliceHarmonization: an integrated method for identifying RNA splicing events in therapeutics for splicing modulation.

MOTIVATION: Splicing, a critical co-transcriptional process in eukaryotes, enhances transcriptome diversity by generating isoforms specific to cell types, tissues, or developmental stages. Recent advancements in splicing modulators have opened new avenues for targeting previously undruggable genes by inducing significant perturbations in splicing events. These developments underscore the need for comprehensive methods to accurately identify and compare splicing events. While several tools have been developed to detect local splice variants, inconsistencies across methods remain a significant challenge. To address this, we present SpliceHarmonization, an integrated approach that combines the strengths of rMATS, LeafCutter, and MAJIQ, enabling robust and reliable splicing analysis with event type annotations. RESULTS: In a comprehensive evaluation using diverse simulated datasets, SpliceHarmonization streamlined and standardized the outputs from three detection methods into a unified format, thereby improving splicing detection with event type annotation and outperforming individual methods. By integrating the outputs from rMATS, LeafCutter, and MAJIQ, our approach not only enhanced identification of a wide range of splicing events but also effectively mitigated method-specific discrepancies. This integration led to an accuracy exceeding 0.8 and a recall of up to 0.5, with an observed increase in AUC of up to 10%. Furthermore, SpliceHarmonization demonstrated high sensitivity in detecting low-abundance and complex splicing events, providing annotations including genomic coordinates and event type. AVAILABILITY AND IMPLEMENTATION: SpliceHarmonization is available at https://github.com/interactivereport/SpliceHarmonization.

RNA Splicing↗

PubMed2026

RNA splicing evidence enables robust classification of BRCA1 exon 18 variants: Results from the ENIGMA consortium.

The Evidence-based Network for the Interpretation of Germline Mutant Alleles (ENIGMA) research consortium conducted a comprehensive study to characterize spliceogenic variants in BRCA1 exon 18. The absence of systematic RNA-based assessment for these variants has led to inconsistent interpretation, limiting accurate classification and management of individuals and their families. The splicing profile of 166 variants was assessed using minigene assays; 32 were additionally analyzed in blood-derived RNA from 51 individuals and 18 in mouse embryonic stem cell (mESC)-based assays to evaluate homology-directed repair (HDR) capacity. mRNA assessment by RT-PCR in blood samples and minigene assays showed a significant positive correlation, with splicing analysis in mESCs displaying highly concordant results. The mESC-based HDR assay showed that the in-frame exon 18 skipping (Δ18) transcript encodes a non-functional protein lacking rescue activity. Linear regression analysis using mESC splicing and functional data indicated that ≥59% of full-length (FL) levels and <34% of Δ18 were associated with benign HDR activity. These thresholds differ from those recommended by the ClinGen ENIGMA BRCA1 and BRCA2 Variant Curation Expert Panel American College of Medical Genetics and Genomics (ACMG)/Association for Molecular Pathology (AMP) specifications for applying BP7_strong(RNA): >30% functional transcripts or <70% non-functional transcripts. Incorporation of RNA splicing evidence into variant interpretation increased pathogenic (28.6%-31.7%) and benign (3.7%-24.4%) classifications while reducing likely pathogenic (19.5%-17.7%), uncertain (18.9%-8.5%), and likely benign (29.3%-17.7%) categories. Experimental mRNA profiling impacted the interpretation of 34% of variants and resolved uncertainty in approximately 10% of cases. Exon 18 skipping was less tolerated, indicating that the degree of splice perturbation required to impair BRCA1 function may depend on the nature of the resulting non-functional transcript.

Humans↗

PubMed2024

Effect of the OPHN1 novel variant c.1025+1 G>A on RNA splicing: insights from a minigene assay.

This research analyzes the clinical data, whole-exome sequencing results, and in vitro minigene functional experiments of a child with developmental delay and intellectual disability. The male patient, aged 4, began experiencing epileptic seizures at 3 months post-birth and has shown developmental delay. Rehabilitation training was administered between the ages of one and two. There were no other significant family medical histories. Through comprehensive family exome genetic testing, a hemizygous variant in the 11th exon of the OPHN1 gene was identified in the affected child: c.1025 + 1G > A. Family segregation analysis confirmed the presence of this variant in the patient's mother, which had not been previously reported. According to the ACMG guidelines, this variant was classified as a likely pathogenic variant. In response to this variant, an in vitro minigene functional experiment was designed and conducted, confirming that the mutation affects the normal splicing of the gene's mRNA, resulting in a 56 bp retention on the left side of Intron 11. It was confirmed that OPHN1: c.1025 + 1G > A is the pathogenic cause of X-linked intellectual disabilities in the child, with clinical phenotypes including developmental delay and seizures.

Humans↗

PubMed2026

A single-cell study of transcription and RNA splicing in MDD and ALC.

Major depressive disorder (MDD) and problematic alcohol use (ALC) commonly co-occur, yet the extent, genomic distribution, and biological context of their shared genetic architecture remain incompletely understood. Here, we integrated genome-wide and local genetic architecture analyses with tissue, spatial, single-cell, and multi-omics analyses to characterize the shared genetic basis of MDD and ALC. Across methods, the two phenotypes showed a consistent positive genetic correlation (rg = 0.380-0.582). MiXeR estimated that they shared approximately 5479 variants with non-zero additive genetic effects, with the shared component accounting for a larger proportion of the polygenic architecture of ALC than of MDD. Local analyses further indicated that shared genetic covariance was concentrated in a limited number of genomic segments. At the tissue and cellular levels, genetic signals were primarily associated with central nervous system tissues and neuronal lineages, with additional support for oligodendrocyte-related populations; the two phenotypes also differed in the distribution and within-cell-type heterogeneity of disease-relevance scores. Multi-omics integration prioritized MED19 and ACO2 as candidate genes and highlighted processes related to mitochondrial energy metabolism and synaptic function. These findings refine the genomic, tissue, and cellular context of the shared genetic architecture of MDD and ALC and provide prioritized genomic regions, cell types, and candidate genes for validation in independent populations and functional studies.

Major Depressive Disorder↗

PubMed2026

An endothelial RNA splicing atlas catalogs effects of IL-1β and identifies an alternative PROCR isoform with genetic links to pleiotropic vascular disease.

Alternative splicing (AS) alters the sequence and dynamics of mRNA but has not been comprehensively annotated in human endothelial cells (ECs). EC dysfunction is a hallmark of complex inflammatory diseases, including cancer and atherosclerosis. Therefore, we modeled inflammation in vitro using 53 genetically distinct human aortic EC lines exposed to interleukin-1β (IL-1β) or control media. This identified 1,224 differentially spliced transcripts (DSTs). DSTs were enriched for alternative first (AF) exon usage, including isoforms of several disease-associated and metabolic genes. To confirm that IL-1β-dependent AF exons were produced by alternative promoters, a quantitative measure of promoter activity was defined using epigenetic data. Ratios of histone 3 lysine 27 acetylation and binding of ERG and RELA between alternative promoters correlated RNA levels of AF exons, confirming our hypothesis. Finally, the effects of genetic variation on AS were investigated by mapping splicing quantitative trait loci (sQTLs). Significant sQTLs were tested for genetic colocalization with cardiovascular risk loci from genome-wide association studies. This identified 66 colocalized signals corresponding to 30 genes and 39 lead variants. The sQTLs identified here provide testable mechanisms explaining some of the genetic risk for vascular disease. For example, genetic association for a previously undescribed isoform of endothelial protein C receptor (PROCR) colocalized with genetic risk for deep vein thrombosis and coronary artery disease with opposing risk alleles. This study demonstrates the prevalence of inducible promoters upon inflammatory stimuli and shows that genetic risk for vascular disease may be in part governed through AS in ECs.

Humans↗

PubMed2025

The RNA splicing factor PRPF8 is required for left-right organiser cilia differentiation and determination of cardiac left-right asymmetry via regulation of Arl13b splicing.

Cilia function in the left-right organizer (LRO) is critical for determining internal organ asymmetry in vertebrates. To further understand the genetics of left-right asymmetry, we isolated a mouse mutant with laterality defects, l11Jus27, from a random mutagenesis screen. l11Jus27 mutants carry a missense mutation in the pre-mRNA processing factor, Prpf8. cephalophŏnus (cph) mutant zebrafish, carrying a protein truncating mutation in prpf8, phenocopy the laterality defects of l11Jus27 mutants. Prpf8 mutant mouse and fish embryos have increased expression of an alternative transcript encoding the cilium-associated protein, ARL13B, that lacks exon 9. In zebrafish, over-expression of the arl13b transcript lacking exon 9 perturbed cilium formation and caused laterality defects. The shorter ARL13B protein isoform lacked interactions with intraflagellar transport proteins. Our data suggest that PRPF8 plays a prominent role in LRO cilia by through the regulation of alternative splicing of ARL13B, thus uncovering a new mechanism for cilia-linked developmental defects.

ARL13B↗

PubMed2026

Pervasive noise in human pre-mRNA splice site selection.

RNA splicing has historically been thought to be highly efficient and accurate, with little opportunity for deviation from regulated alternative splicing. This dogma has been challenged by recent observations that biological noise may contribute substantially to transcriptome diversity. However, quantitative understanding of stochastic splicing variation is challenging because these transcripts are likely subject to rapid degradation. Here, we use deep sequencing across RNA compartments to track splicing intermediates in human cells and see abundant cryptic splicing associated with genomic features that promote splicing noise. We observe pervasive usage of low-fidelity splice sites, likely due to stochasticity in recruitment or binding of the spliceosome. These sites are turned over quickly and show evidence for nuclear and cytoplasmic degradation, suggesting widespread surveillance and rapid quality control of non-productive transcripts. Our findings provide insights into the propensity for error in RNA processing mechanisms and regulation of alternative splice sites across a gene.

Humans↗

PubMed2025

Pervasive noise in human splice site selection.

RNA splicing has historically been thought to be highly efficient and accurate, with little opportunity for deviation from regulated alternative splicing decisions. This dogma has been challenged by recent observations that suggest that biological noise may contribute substantially to transcriptome diversity. However, quantitative understanding of stochastic variations in splicing is challenging because these transcripts are likely subject to rapid degradation. Here, we use ultra-deep sequencing across RNA compartments to track splicing intermediates in human cells and see abundant cryptic splicing associated with genomic features that promote splicing noise. We observe pervasive usage of low-fidelity splice sites, likely due to stochasticity in recruitment or binding of the spliceosome. These sites are most likely degraded in the nucleus rather than targeted by translation-dependent degradation processes, suggesting widespread surveillance and rapid quality control of non-productive RNA transcripts. Our findings provide unprecedented insights into the propensity for error in RNA processing mechanisms and the regulation of alternative splice sites across a gene.

Journal Article↗

PubMed2026

MAJIQ-CLIN: A novel tool to help identify Mendelian disease-causing variants from RNA-seq data.

PURPOSE: The current diagnostic rate for patients with suspected Mendelian genetic disorders is low, despite exome/genome sequencing being the standard of care. One reason for this low diagnostic rate is that traditional exome/genome sequencing analysis methods struggle to detect RNA splicing aberrations. Causative variants often involve splicing changes, with numerous splice-altering variants being responsible for known Mendelian disorders. Therefore, it is crucial to develop reliable tools to detect, quantify, prioritize, and visualize RNA splicing aberrations from patient RNA sequencing data. METHODS: We developed Modeling Alternative Junction Inclusion Quantification for Clinical Applications (MAJIQ-CLIN), a method to identify RNA splicing aberrations in patients' RNA sequencing data compared with a cohort of control samples. MAJIQ-CLIN can efficiently process large datasets, avoiding reprocessing when new data are added, while effectively detecting local splicing variations with deviations in a given patient, termed outlier local splicing variation, or unique to the patient, termed private local splicing variation. RESULTS: We performed a systematic evaluation of the accuracy of tools for detecting patients' RNA splicing aberrations from RNA sequence using synthetic data across several aberration types and transcript inclusion levels. Then, we used several real datasets to assess MAJIQ-CLINs ability to identify solved test cases and control for the effect of confounders such as batches. We showed that MAJIQ-CLIN compares favorably to existing tools in both accuracy and efficiency. We also used MAJIQ-CLIN to investigate several unsolved patient cases from the Undiagnosed Diseases Network. CONCLUSION: MAJIQ-CLIN offers an efficient, accurate, and user-friendly tool to aid in diagnosing Mendelian disease-causing variants from RNA sequence data.

Bioinformatics↗

PubMed2025

Oncogenic DEAD-box ATPase DDX41 establishes transcript ensembles via CLK3-dependent and -independent mechanisms.

Post-transcriptional diversification of RNA transcripts mediated by complex processing machinery, including DEAD-box ATPases, establishes and maintains cellular phenotypes. For example, DDX41 controls RNA splicing, innate immune signaling, and genome stability. Although heterozygous DDX41 germline genetic variation occurs in familial myelodysplastic syndrome (MDS) and acute myeloid leukemia (AML), the DDX41 contributions to splicing globally, biological processes, and pathogenic mechanisms are incompletely defined. Using a genetic rescue system with Ddx41+/- myeloid progenitors, we established global wildtype DDX41 and pathogenic variant mechanisms. Differing from pathogenic variants of other RNA splicing regulators, DDX41 deficiency compromised multiple splicing steps. DDX41-regulated transcripts encoded factors controlling RNA splicing, including Cdc2-like kinase 3 (CLK3). DDX41 regulated Clk3 transcripts, and elevated CLK3 during myeloid differentiation. Loss-of-function analysis revealed DDX41-regulated splicing commonly, but not always, required CLK3. Thus, through a mechanism utilizing a splicing factor kinase that itself is DDX41-regulated, DDX41 establishes transcript ensembles in myeloid progenitors.

DEAD-box RNA Helicases↗

PubMed2026

CNOT1 is a potential YTHDF2 target that orchestrates maternal mRNA decay and zygotic genome activation during goat embryogenesis.

Timely and efficient degradation of maternal mRNA is essential for early embryonic development, which occurs from fertilization through the initiation of zygotic genome activation (ZGA). Yet, the regulatory mechanisms governing this process remain poorly characterized. In the present study, we investigated the function of CCR4-NOT transcription complex subunit 1 (CNOT1) during goat embryogenesis. We found that CNOT1 was upregulated during mammalian ZGA, and that its knockdown led to developmental arrest and a marked reduction in blastocyst formation. Moreover, CNOT1 knockdown impaired nascent RNA activity, resulting in 814 upregulated and 1014 downregulated genes, which were enriched for RNA splicing, regulation of chromosome organization, and RNA localization. RNA splicing analysis revealed differential splicing events in 2959 genes, of which 259 were downregulated following CNOT1 knockdown. Notably, CNOT1 was predicted to crosstalk with the m6A reader YTHDF2. Knockdown of YTHDF2 resulted in CNOT1 downregulation at the 8-cell stage in goats and increased transcription levels around polyadenylation sites during ZGA in mice. Together, these findings indicate that CNOT1 is a potential YTHDF2 target that orchestrates maternal mRNA decay and ZGA during goat embryogenesis. Our work provides new insight into the complex regulatory landscape underlying ZGA and may inform strategies to improve the efficiency of goat embryogenesis.

Animals↗

PubMed2025

Alternative pre-mRNA Splicing and Gene Expression Patterns in Midbrain Lineage Cells Carrying Familial Parkinson's Disease Mutations.

Parkinson's disease (PD) arises from genetic and environmental factors. Human genetics has identified mutations in ~20 inherited familial genes linked to monogenic forms of PD. To investigate the effects of individual familial PD mutations, human pluripotent embryonic stem cells (hPSCs) carrying 12 distinct familial PD mutations were differentiated into midbrain lineage cells, including dopaminergic (mDA) neurons. Global gene expression and pre-mRNA splicing patterns were analyzed in midbrain cultures carrying pathogenic PD mutations in the PRKN, SNCA, LRRK2, PINK1, DNAJC6, FBXO7, SYNJ1, DJ1, VPS13C, ATP13A2 and GBA1 genes. This analysis revealed that these familial PD mutations lead to pre-mRNA splicing changes linked to RNA splicing factors and to pathways controlling cell projections, cytoskeleton, GTPase regulation and others. Importantly, we have also shown that subsets of these splicing changes overlap with changes found in PD patient postmortem brains. Mutation-specific pre-mRNA isoforms may function as both diagnostic biomarkers for familial PD-associated genotypes and promising therapeutic targets.

Journal Article↗

PubMed2025

Identifying novel heterozygous PI4KA variants in fetal abnormalities.

BACKGROUND: The clinical manifestations of PI4KA-related disorders are characterized by considerable variability, predominantly featuring neurological impairments, gastrointestinal symptoms, and a combined immunodeficiency. The aim of this study was to delineate the novel spectrum of PI4KA variants detected prenatally and to assess their influence on fetal development. METHODS: A thorough fetal ultrasound screening was conducted, supplemented by both antenatal and post-abortion magnetic resonance imaging (MRI) studies. Novel PI4KA variants were detected through clinical Whole exon sequencing (WES) and validated by Sanger sequencing. The functional consequences of these variants were evaluated using bioinformatics tools. The effects of the identified variants on splicing were analyzed through minigene splicing assays. Subsequently, both wild-type and mutant PI4KA protein fragments were purified, and their enzymatic activities were quantitatively assessed. RESULTS: Ultrasound imaging, MRI scans revealed a dilated small intestine with an obstruction. Compound heterozygous variants (NM_058004.3: c.2802_2863-40del and c.2819 C > T, p.Ala940Val) were identified in the PI4KA of the affected fetus through clinical trio-WES. Both variants were predicted deleterious. The PI4KA variant c.2802_2863-40del resulted in the production of three distinct mRNA isoforms. The PI4KA variant c.2819 C > T (p.Ala940Val) significantly reduced the enzyme activity. CONCLUSIONS: This study extended the mutational spectrum of PI4KA and may provide guidance for genetic counseling. Functional studies confirmed that the identified variant induces alterations in RNA splicing and impairs enzyme activity.

Adult↗

PubMed2025

A six-repeat PPR protein WPR directly binds target RNAs and coordinates chloroplast RNA processing via dual recruitment of MORF1, MORF8b, and CAF2 proteins in rice.

Pentatricopeptide repeat (PPR) proteins are key regulators of organelle RNA metabolism in plants, yet their precise mechanisms in chloroplast RNA processing remain unclear. Here, we identify WPR, a unique P-type PPR protein in rice (Oryza sativa L.), as a critical factor in chloroplast RNA splicing and editing. A ~112-kb chromosomal inversion upstream of WPR causes an albino panicle rachis phenotype (wpr mutant), while complete loss of WPR function leads to seedling lethality. WPR deficiency disrupts the splicing of multiple group II introns (atpF, ndhA, ndhB, petB, rpl2, and rps12) and impairs RNA editing in transcripts such as ndhA, ndhB, ndhG, rps14, and ycf3. Electrophoretic mobility shift assay (EMSA) data confirm that WPR directly binds to precursor mRNAs of atpF, ndhA, petB, rpl2, and rps12. Strikingly, WPR interacts with both RNA editing factors (MORF1, MORF8b) and the splicing factor CAF2, but not with other PPR proteins targeting the same transcripts. Unlike most PPR proteins, WPR contains only six PPR repeats, which is the fewest among all functionally characterized rice PPR proteins. With few informative repeats, WPR likely possesses a broad, low-specificity RNA-binding activity. Moreover, WPR may act on chloroplast RNA maturation by recruiting MORFs and CAF2 rather than other PPR proteins, highlighting a novel regulatory mode in which P-type PPR protein may act as an RNA-binding scaffold to integrate diverse RNA-processing machineries. This study advances the understanding of PPR protein diversity and provides new insights into the molecular mechanisms of chloroplast RNA processing in rice.

Oryza↗

PubMed2026

Targeting PRMT9 overcomes venetoclax resistance in AML by modulating splicing and inhibiting translation.

Arginine methylation catalyzed by protein arginine methyltransferases (PRMTs) is required for cancer cell proliferation, but whether PRMTs mediate resistance to therapy remains unclear. Here, we performed loss-of-function screens in venetoclax-resistant (VEN-R) acute myeloid leukemia (AML) patient-derived xenograft cells and found that PRMT9 plays a critical role in promoting VEN resistance. Specifically, VEN-R AML samples exhibited high levels of PRMT9, and PRMT9 inhibition resensitized AML cells to VEN treatment. In preclinical resistant models, genetic ablation of PRMT9 synergized with VEN to eradicate AML cells. Consistently, pharmacologic inhibition of PRMT9 combined with VEN produced similar effects in VEN-R AML mouse models. Mechanistically, PRMT9 ablation disrupted RNA splicing by inducing exon skipping in mRNA encoding ALG13, an uridine diphosphate (UDP)-N-acetylglucosaminyltransferase subunit, thereby downregulating expression of the VEN efflux transporter encoded by the adenosine triphosphate-binding cassette subfamily C member 1 gene. PRMT9 inhibition also suppressed protein synthesis, leading to downregulation of short-lived oncoproteins such as MCL1. These findings establish a connection between PRMT9-mediated arginine methylation and poor VEN responsiveness and demonstrate that targeting PRMT9 may represent a viable strategy to overcome VEN resistance.

Protein-Arginine N-Methyltransferases↗