The team first fed mice a high-fat diet and observed lower PQBP1 levels in the cerebral cortex, a brain region involved in cognitive functions. PQBP1 regulates alternative RNA splicing, a process that allows a single gene to generate different RNA transcripts and potentially different protein isoforms. The researchers linked the diet-associated reduction in PQBP1 to suppressed PPARγ-mediated transcription of the PQBP1 gene. They also implicated insulin-related signaling as a possible upstream mechanism, but the supplied study description does not establish whether that signaling change is a direct cause of the reduction.

To examine the cellular consequences, the scientists used RNA-sequencing-based analyses to compare splicing patterns in mice fed a high-fat diet for one or six weeks with those in mice lacking PQBP1 in neurons. Both conditions shared changes in the alternative splicing of specific genes associated with synaptic function. Additional experiments indicated that abnormal splicing of these downstream genes was associated with abnormalities in synaptic structure and function. These molecular and cellular changes occurred alongside impaired cognitive performance, linking diet-associated changes in gene regulation with impaired neuronal communication. The work was conducted in mice, and the reported effects should therefore not be interpreted as evidence that the same pathway causes cognitive decline in humans.

The researchers also tested whether selected molecular changes could be reversed in mice. Pioglitazone, a diabetes drug that activates PPARγ, restored PQBP1 levels in mice receiving the high-fat diet. It also corrected abnormal RNA splicing in key synapse-related genes and improved synaptic and cognitive outcomes. A separate gene-therapy approach that restored PQBP1 rescued synaptic and cognitive deficits, while restoring particular downstream genes also produced beneficial effects. These interventions were tested in the same experimental setting rather than in a human clinical trial, and their results show that the measured pathway can be modulated in affected mice. The findings identify PQBP1-dependent alternative RNA splicing as a potential therapeutic target for further investigation, but the study does not establish that pioglitazone or gene therapy is safe or effective for diet-associated cognitive impairment in people.

Subject of Research: Experimental mouse study of PQBP1-dependent RNA splicing in high-fat diet-induced cognitive impairment

Article Title: Exploring the correlation between high calorie diet and cognitive impairment

Article References: Exploring the correlation between high calorie diet and cognitive impairment. Original publication (Bibliographic details unavailable.)

Image Credits: AI Generated

DOI: Not provided

Keywords: high-fat diet, cognitive impairment, PQBP1, RNA splicing, synaptic dysfunction, cerebral cortex, PPARγ, pioglitazone, gene therapy, mouse study, Exploring, correlation

The donor study, published in PLOS One, recruited volunteers aged 25 to 55 at Shenzhen Blood Center between August 1, 2022, and May 31, 2025. Fresh blood samples were obtained with written informed consent under approval from the blood center’s research ethics committee. Each participant carried at least one JK*A allele, and PacBio long-read sequencing of genomic DNA was used to confirm the integrity of SLC14A1 and determine selected haplotypes.

For transcript analysis, the researchers extracted total RNA from the red-cell layer, where reticulocytes made SLC14A1 messenger RNA detectable. They synthesized complementary DNA, amplified the SLC14A1 open reading frame with two rounds of nested PCR, and used PacBio long-read sequencing to examine exon composition and sequence variation. Analysis of 4,895 valid reads from participant W7, for example, showed that multiple transcript patterns occurred within a single sample.

The investigators identified two potential exon regions not previously described, designated PER-4 and PER-5. PER-4 occurred in 19.16% of valid reads from donor N8, who showed normal Jka presentation, while PER-5 occurred in 12.17% of valid reads from donor W10, who showed weak presentation. Both events introduced frameshifts relative to the corresponding reference transcript variants. These were individual observations rather than group-level estimates of a new splicing pattern.

Donor W3 illustrated a different type of alteration. PER-9 through PER-11 were absent from all detected transcripts, although the corresponding regions were present in genomic DNA and no mutations were found at adjacent exon-intron junctions. The study located the Jka-associated position at nucleotide 838 in PER-11, so its complete absence was consistent with a contribution to W3’s weak phenotype. The finding applied to one individual and did not establish the proportion of normal PER-11-containing transcripts required to produce weak serological reactivity.

Patterns involving PER-6 and PER-7 also differed between the two phenotype groups. PER-6 appeared in more than 80% of valid reads from Jk(a + w) donors, compared with about 40% in donors with normal Jka presentation, and the authors reported statistically significant group differences. Skipping these potential exons could create a different start codon and a truncated SLC14A1 isoform. The authors proposed that transcript variation may influence antigen presentation, while calling for further work to determine the alternative start codon’s translation efficiency and compare the antigenic properties of the resulting protein isoforms.

Sequence differences were also detected in transcripts but not in matched genomic DNA. Examples included a G deletion in donor W2 and an A insertion in donor N7, both verified by Sanger sequencing. The researchers interpreted these observations as evidence of transcript-level errors, including insertions and deletions at or near the 130G/A single-nucleotide variant. In a focused analysis of six Jk(a + w) donors and four normal Jka donors, the frequency of these changes around 130A was higher than around 130G in every participant, regardless of phenotype.

For donor W6, 587 of 2,229 reads carrying 130A contained indels within the six-nucleotide region, an indel rate of 26.33%; the corresponding rate for 130G was 12.44%. Indel rates around both 130A and 130G were also reported to be significantly higher among Jk(a + w) donors than among normal Jka donors. The authors interpreted the group pattern as evidence of lower observed transcription fidelity in the weak-presentation group, rather than a direct demonstration that such errors caused the phenotype.

The researchers also tested whether reverse transcription or PCR amplification could explain the sequence changes. Products amplified directly from sequence-confirmed plasmids had fewer mismatches and indels than products obtained after in vitro-transcribed RNA underwent reverse transcription and PCR. This showed that some artifacts can arise during those procedures, but their rates in the six-nucleotide region were much lower than those observed in donor samples. The authors therefore judged the artifacts unlikely to account for the main findings while acknowledging the need for additional investigation.

The study was limited by its sample of 18 donors from one blood center, including only 10 participants with weak Jka presentation. It assessed transcript structure and sequence but did not directly measure the antigenic activity or expression of each predicted SLC14A1 protein isoform. The findings therefore identify transcript alterations as factors associated with weak Jka presentation, without showing that they alone cause the phenotype or establishing their usefulness in routine donor testing.

Subject of Research: SLC14A1 transcript structure and weak Jka antigen presentation in Chinese blood donors

Article Title: Alterations of SLC14A1 mRNA structure are frequently detected in weak Jk a presenting donors

Article References: Liang, S., Liang, Y., Wu, F., Liu, T., Sun, L., Luo, B., Wang, Y., Liu, Y., Feng, B., & Ren, J. (2026). Alterations of SLC14A1 mRNA structure are frequently detected in weak Jka presenting donors. PLOS One, 21(10), e0360437. https://doi.org/10.1371/journal.pone.0360437

Image Credits: AI Generated

DOI: 10.1371/journal.pone.0360437

Keywords: SLC14A1, Kidd blood group, Jka antigen, weak Jka phenotype, RNA splicing, transcription errors, PacBio sequencing, blood donors, transfusion medicine, Alterations, mRNA, structure

CLN7 disease, also known as variant late-infantile neuronal ceroid lipofuscinosis, is a lysosomal storage disorder caused by biallelic defects in MFSD8. The gene encodes major facilitator superfamily domain-containing protein 8, also called the CLN7 protein, a 518-amino-acid lysosomal transmembrane protein whose precise function remains incompletely understood but is considered essential for normal neuronal homeostasis. Current evidence suggests that MFSD8 may function as a chloride channel involved in lysosomal enzyme trafficking. Classic CLN7 disease typically begins between the ages of two and seven years and can involve seizures, motor impairment, progressive mental regression, myoclonus, speech impairment, vision loss and personality disorders. More broadly, neuronal ceroid lipofuscinoses are estimated to occur in one to four people per million live births, with frequencies varying by genetic subtype and population.

The proband was the first and only child of healthy, non-consanguineous Russian parents. She was born at 38 weeks after an uncomplicated pregnancy, apart from a first-trimester threatened miscarriage. Her birth weight was 3,170 g, her length was 52 cm, and her Apgar scores were 8 and 8. Early motor and speech development was initially within normal limits: she walked independently at 13 months and used phrase speech by two years and four months. At approximately four years of age, subtle cognitive and behavioral changes appeared, including reduced attention and memory. Her first atonic seizure occurred during a febrile illness at four years and ten months. Recurrent afebrile atonic seizures followed, and myoclonic seizures began at five years and two months.

As the illness progressed, the child developed progressive intention tremor, gait ataxia, dysarthria and motor incoordination. From the age of six, her neurological deterioration accelerated. She lost expressive speech, regressed in fine and gross motor skills and lost control of her bladder and bowels. By six and a half years, she could no longer walk independently; later, she could not sit or feed herself. A neurological examination at six years and eight months showed severe developmental regression, absent speech, generalized hypotonia with brisk deep tendon reflexes and ankle clonus, marked upper-limb, head and trunk tremor, truncal ataxia, impaired fixation and complete loss of independent ambulation. She was underweight, with a weight of 21 kg and a BMI of −2.9 standard deviations, and had an acquired head circumference of 50 cm, or −1.1 standard deviations, despite a height of 132 cm, or +2.64 standard deviations.

Brain magnetic resonance imaging revealed diffuse cerebral and cerebellar atrophy. Video electroencephalography showed diffuse background slowing with generalized spike/polyspike-and-slow-wave discharges and a posterior photoparoxysmal response during intermittent photic stimulation. Ophthalmological examination found only subtle optic disc pallor, without clinically significant retinal degeneration at the time of evaluation. By eight years and two months, the patient was bedridden, had lost the ability to swallow independently and required gastrostomy feeding. She also developed severe sleep disturbances requiring pharmacological treatment, while her seizures became more frequent and could be terminated only with injectable midazolam. The clinical course therefore combined childhood-onset epilepsy, progressive developmental regression, ataxia, loss of motor and speech function, and cerebral and cerebellar atrophy.

The initial diagnostic evaluation did not reveal a cause. Routine metabolic investigations, lysosomal enzyme assays, echocardiography, nerve-conduction studies, serum creatine kinase analysis and whole-exome sequencing were all unremarkable. Trio whole-genome sequencing subsequently identified the homozygous deep intronic MFSD8 variant c.999-556C>G, with each parent carrying a heterozygous copy. The variant was absent from gnomAD version 4.1.1 and had not previously been reported in ClinVar or the literature. Its intronic location meant that its effect could not be established from DNA sequence alone, particularly because noncoding variants cannot usually be interpreted from the nucleotide change without functional evidence. The investigators therefore tested the variant at the RNA level to determine whether it altered MFSD8 splicing.

SpliceAI predicted that c.999-556C>G would create cryptic splice sites with a delta score of 0.73 for the acceptor and 0.67 for the donor, resulting in inclusion of a 98-nucleotide pseudoexon. To evaluate that prediction, the researchers isolated RNA from cultured skin fibroblasts of the proband and her heterozygous father. They amplified the region spanning exons 6 through 12 by reverse-transcription polymerase chain reaction and analyzed the products through targeted next-generation sequencing, using RNA from a healthy donor fibroblast culture as a control. Targeted sequencing confirmed inclusion of the predicted pseudoexon at chromosome 4 positions 127,922,520–127,922,617 in RNA from the proband and her father. Both individuals had a canonical transcript and an aberrant transcript containing the pseudoexon.

Pseudoexon inclusion caused a frameshift and generated the premature termination-codon allele p.(Ile334Valfs*113). Among the MFSD8 transcript molecules detected in the targeted amplicon from the homozygous proband, 84% contained the pseudoexon. In the heterozygous father, the aberrant isoform accounted for 12% of the detected transcripts. These figures describe relative proportions within the analyzed RNA amplicons, rather than absolute transcript abundance. The lower proportion in the father is compatible with partial degradation of the premature-termination-containing RNA by nonsense-mediated decay, although the contribution of that mechanism could not be directly quantified because no informative heterozygous exonic variants were available for allele-specific analysis. Treating the father’s fibroblasts with a nonsense-mediated-decay inhibitor increased the relative abundance of the pseudoexon-containing transcript by approximately 1.7-fold, but it did not restore the fraction to the roughly 50% expected for a heterozygous genotype.

An independent minigene assay reproduced the splicing defect in an engineered system. The construct carrying the mutant sequence generated predominantly the aberrant transcript containing the 98-nucleotide pseudoexon, which accounted for 84.3% of transcripts, together with a minor canonical population of 15.5%. By contrast, the wild-type construct generated only the canonical transcript. The mutant construct’s continued production of some canonical RNA indicates that the variant strongly promotes aberrant splice-site recognition without completely abolishing recognition of the normal splice sites. The abundance of canonical transcripts in the minigene system cannot, however, be extrapolated directly to the endogenous MFSD8 locus or used to infer the amount of functional MFSD8 protein remaining in the patient. In combination with the clinical concordance and the findings in patient-derived RNA, the minigene result supports a causal relationship between c.999-556C>G and the abnormal splicing event. The authors consequently classified it as the causative mutation and considered other variants found by whole-genome sequencing unlikely to be disease-causing.

The case illustrates why deep intronic variants can escape routine diagnosis. Exon-focused sequencing may miss pathogenic changes located within introns, while DNA analysis alone may not establish what a noncoding variant does to RNA processing. The findings show how genome sequencing can identify a candidate regulatory change and how transcript analysis can directly test its effect at the endogenous gene. The report nevertheless remains a single-patient case: it does not establish how frequently this mechanism occurs in CLN7 disease, how it is distributed across populations or whether the same variant produces the same clinical course in other people. It nevertheless adds a distinct deep intronic allele to an MFSD8 spectrum already known to include missense, nonsense, frameshift, splice-site and copy-number variants. The absence of prominent retinal degeneration in this patient, despite severe neurological progression, also documents variability within the clinical presentation of CLN7 disease. A patient-specific antisense oligonucleotide has previously been developed for pseudoexon inclusion in another MFSD8-related case, and the clearly defined splicing defect reported here may provide a measurable molecular endpoint for individualized therapeutic studies, but no treatment was tested in this case report.

Subject of Research: Functional characterization of a deep intronic MFSD8 variant associated with CLN7 disease

Article Title: Case Report: A novel deep intronic MFSD8 splice-altering variant causes CLN7 disease through pseudoexon inclusion

Article References: Akimova, D., Voskanyan, A., Orlova, A., & Skoblov, M. (2026). Case Report: A novel deep intronic MFSD8 splice-altering variant causes CLN7 disease through pseudoexon inclusion. Frontiers in Genetics, 17, Article 1980180. https://doi.org/10.3389/fgene.2026.1980180

Image Credits: AI Generated

DOI: 10.3389/fgene.2026.1980180

Keywords: MFSD8, CLN7 disease, deep intronic variant, pseudoexon inclusion, RNA splicing, whole-genome sequencing, rare disease genetics, neuronal ceroid lipofuscinosis, patient-derived fibroblasts, minigene assay, Case, Report

The variant in question, HNRNPH2-R114W, affects a gene on the X chromosome that encodes a member of the heterogeneous nuclear ribonucleoprotein family. These proteins bind G-rich RNA motifs and help decide where precursor messenger RNA is cut and rejoined during splicing, the process that generates the diverse protein-coding transcripts a cell needs. Pathogenic variants in HNRNPH2 cause Bain type X-linked syndromic intellectual developmental disorder, a condition marked by severe developmental delay, absence of verbal communication, impaired ambulation, seizures, and prominent autistic features. The individual whose cells seeded this study carries a de novo heterozygous R114W missense variant and exhibits precisely this severe clinical profile.

To study the variant in a controlled setting, the team reprogrammed the patient’s peripheral blood mononuclear cells into induced pluripotent stem cells using non-integrating episomal vectors. One stem cell line, designated Minus, retained the R114W variant. A second line, designated Plus, was generated by correcting the HNRNPH2 locus with CRISPR-Cas9 within the same genetic background, and Sanger sequencing confirmed the correction-associated sequence changes in edited clones. Both lines maintained strong nuclear expression of the pluripotency markers POU5F1 and NANOG, and both were differentiated into cerebral organoids following a modified Lancaster protocol that included embryoid body formation, neural induction, Matrigel embedding, and suspension maturation.

Imaging told a reassuring story about gross development. Whole-mount immunostaining showed PAX6-positive progenitors arranged in radial, ventricular-like zones around central lumens, with TUBB3-positive neurons localizing to peripheral regions in both genotypes. Organoids from the variant and corrected lines were comparable in size and morphology, with no observable structural abnormalities. HNRNPH2 immunofluorescence, however, revealed genotype-dependent differences: corrected organoids showed signal concentrated in neuroepithelial regions, while variant organoids exhibited weaker and more diffuse staining. The authors interpret this as an indirect indicator of altered HNRNPH2 distribution rather than definitive evidence of reduced protein abundance, since the assay relied on immunofluorescence alone without orthogonal protein quantification.

The transcriptomic analysis, though exploratory in design, produced striking results. Bulk RNA sequencing was performed on pooled RNA from approximately twelve organoids per genotype, each pool sequenced in two technical reactions at a single developmental time point. Differential expression analysis with DESeq2 showed near-complete separation of the two genotypes along the first principal component, which accounted for 99.5 percent of the variance. Thousands of genes were differentially expressed at a false discovery rate of 0.05, with roughly equal numbers upregulated and downregulated. Genes downregulated in variant organoids were enriched for neuron differentiation, axon development, and synaptic transmission, while upregulated genes pointed toward WNT and NOTCH signaling, melanogenesis, tyrosine metabolism, and retinoid biosynthesis.

The splicing findings were even more dramatic. Using SGSeq to quantify both annotated and novel splice junctions supported by split reads, the researchers identified 6,310 differentially used junctions out of roughly 98,000 examined, meaning about six to seven percent of all junctions were significantly altered. By contrast, the exon-focused workflow, which used featureCounts and voom-limma diffSplice testing, found only 17 significant exons. This junction-dominant pattern is biologically coherent: HNRNP H-family proteins regulate splice-site selection at G-rich motifs, so a variant that disrupts their RNA engagement would be expected to reorganize local donor-acceptor usage rather than simply delete exons. Corrected organoids showed increased junction usage in genes such as TUBA1A, TUBB3, CNTN2, and CKB, while variant organoids showed higher usage in DCT, PMEL, ALDH1A3, RDH10, CALB1, and XIST.

Computational structural modeling provided a mechanistic hypothesis for how the variant acts. The researchers built a composite model of HNRNPH2’s three quasi-RNA recognition motifs from available crystal structures and docked it relative to the spliceosomal B complex. In this arrangement, residue R114 sits near a predicted RNA-contact interface within the RRM2 domain, positioned in a geometry compatible with direct RNA interactions. The R114W substitution, replacing a positively charged arginine with a bulky tryptophan, would be predicted to alter this interface and change how the protein engages its RNA targets. The authors emphasize that this docking framework is hypothesis-generating and requires extended simulations and direct structural validation, for example through cryo-electron microscopy.

To organize the multi-layered RNA signals, the team developed an integrated prioritization framework that combined differential expression, event-level splicing significance, and isoform-level remodeling into a composite score per gene. This analysis identified regulatory hubs enriched for axon guidance and synaptic signaling, including CNTN2 and NCAM1, which are critical for cortical wiring, along with TRPM3, HES5, HES6, RTN4, and HMGCS1, which participate in neuronal excitability, neurogenesis, and metabolic support. Some genes, such as RUFY3, EFS, SPAG9, CRMP1, HNRNPC, UTRN, and EVL, showed significant splicing changes without detectable expression shifts, indicating post-transcriptional regulation of neuronal projection and cytoskeletal pathways. Others, including CDH6 and PTPRS, exhibited combined transcriptional and exon-usage alterations.

A key question in organoid transcriptomics is whether apparent gene expression changes reflect genuine regulatory effects or merely shifts in cell-type composition. To address this, the researchers applied MuSiC deconvolution against the human neural organoid cell atlas, a single-cell reference of neurodevelopment. Both genotypes contained mixtures of neuroepithelium, dorsal and ventral telencephalic neurons, glioblasts, oligodendrocyte progenitors, and astrocytes. Variant organoids showed modest enrichment of neuroepithelial and glial-associated fractions and a neuronal fraction approximately five percent lower than corrected organoids. Curated marker heatmaps supported this inference, with progenitor markers such as PAX6 and SOX2 and astrocyte markers GFAP, S100B, and AQP4 showing genotype-linked patterns. The authors conclude that these modest compositional shifts are unlikely to account for the extent of transcriptional and splicing alterations observed, suggesting the variant biases developmental timing toward progenitor and glial states rather than causing neuronal loss.

The findings support a model in which HNRNPH2 variants disrupt post-transcriptional regulation through altered protein localization, splicing, and ribonucleoprotein assembly, producing toxic or dominant-negative effects rather than simple loss of function, with limited compensation by the paralog HNRNPH1. Beyond clarifying disease mechanism, the study nominates candidate isoform-level endpoints for therapeutic investigation, including assessment of allele-selective antisense oligonucleotide strategies and HNRNPH2 modulation in human cortical organoids. The authors also propose that their integrative methodology, combining differential expression, multi-layer splicing analysis, and single-cell-based deconvolution, could be applied to other RNA-binding protein-driven neurodevelopmental disorders, opening avenues to examine how HNRNPH2-associated RNA dysregulation evolves across developmental time and recurs across independent biological contexts.

Subject of Research: HNRNPH2-R114W remodels RNA splicing and neurodevelopmental gene programs in isogenic cerebral organoids

Article Title: HNRNPH2-R114W remodels RNA splicing and neurodevelopmental gene programs in isogenic cerebral organoids

Article References: Caiaffa, C. D., Ghousifam, N., Watkins, S. L., Nakaya, H. I., Bowling, R. A., Jr., Finnell, R. H., & Cabrera, R. M. (2026). HNRNPH2-R114W remodels RNA splicing and neurodevelopmental gene programs in isogenic cerebral organoids. Frontiers in Bioengineering and Biotechnology, 14, Article 1922305. https://doi.org/10.3389/fbioe.2026.1922305

Image Credits: AI Generated

DOI: 10.3389/fbioe.2026.1922305

Keywords: HNRNPH2-R114W, remodels, splicing, neurodevelopmental, gene, programs, isogenic, cerebral, organoids, scientific research

The scientific foundation for this work was laid two decades ago. In 2006, Shinya Yamanaka demonstrated that over-expressing just four transcription factors, now universally known as the Yamanaka factors, could reprogram mature cells all the way back to a pluripotent, embryonic-like ground state. The discovery earned a Nobel Prize and reshaped developmental biology. What followed was an even more tantalizing observation for aging researchers: when the Yamanaka factors are expressed only in short, carefully timed bursts, they can partially reprogram old cells into a more youthful condition, reversing multiple hallmarks of aging while the cells retain their specialized functions. The implication was profound. Aging, it seemed, does not have to be a one-way street, and even old cells retain a latent capacity for rejuvenation that modern biology might learn to unlock.

Yet the therapeutic promise of the Yamanaka factors has always been shadowed by a serious risk. Because these factors can drive cells all the way back to a pluripotent state, their over-expression raises the danger of cancer formation, and controlling exactly how far the reprogramming proceeds remains a formidable technical challenge. Alex Plesa, a scientist at the Wyss Institute and first co-author of the new study, framed the dilemma succinctly: in reprogramming, there is a fundamental tradeoff between rejuvenation and cell identity, and achieving one without losing the other requires walking a fine line. That tradeoff has motivated a worldwide search for alternative factors that might rejuvenate aging tissues in safer and more controllable ways, and it is precisely this search that the Harvard-led team set out to systematize.

Their first challenge was measurement. How do you score rejuvenation reliably enough to screen hundreds of candidate genes? The most widely used tool, the epigenetic aging clock, reads chemical modifications to the genome that accumulate with age. But as Plesa explained, that approach does not scale well to screening because of high costs and the difficulty of interpreting its widespread changes. Instead, the team reasoned that any genuine rejuvenation process must ultimately manifest itself in altered gene expression programs that restore more youthful cellular functions. Gene expression, they concluded, was the right readout. Working with Antonio del Sol, an Ikerbasque Research Professor at CIC bioGUNE-BRTA in Spain, and postdoctoral fellow Sascha Jung, the study’s co-first author, they built a machine learning algorithm trained on transcriptomic profiles spanning multiple aging processes in human skin fibroblast cells from donors across a wide age range.

The resulting tool, which the team calls a transcriptomic aging model, functions something like a set of odometers for different parts of a car. It tracks changes in the expression of genes involved in distinct biological processes and integrates them into a single accurate overview of a cell’s age and health. Trained on gene expression data from 464 fibroblast samples, the model could pinpoint the transcriptomic age of skin cells from individual donors. Crucially, it also proved sensitive to real biological change: when the researchers treated fibroblast cell lines derived from donors aged 55, 65, and 79 with experimental lifespan-altering interventions, including the Yamanaka factors, the predictor accurately registered the resulting shifts in transcriptomic age. The team now had a scorable, quantitative yardstick for rejuvenation.

With that yardstick in hand, the researchers assembled a focused library of genes predicted to influence aging processes and over-expressed each one in aged fibroblast cell lines, hunting for candidates that could shift the cells’ aging score toward a more youthful value. One gene rose decisively to the top: SRSF1, which encodes an RNA processing factor. Over-expression of SRSF1 reduced features corresponding to several recognized hallmarks of aging, including cellular senescence, the state in which damaged cells stop dividing but refuse to die; proteostatic stress, a disruption of the normal balance and turnover of proteins; and inflammaging, the chronic low-grade inflammation that accompanies aging. The rejuvenation effects also registered on the conventional epigenetic aging clock and extended to the restoration of DNA repair programs, suggesting a broad and genuine reversal of age-associated molecular damage.

Just as important as what changed was what did not. The rejuvenated fibroblasts maintained their identity throughout the intervention. They kept their characteristic spindle-shaped morphology, continued expressing the genes that encode typical fibroblast functions, and did not activate the pluripotency programs that Yamanaka factors switch on. In other words, SRSF1 appears to rejuvenate cells by working through machinery that all cells already use, rather than overriding their identity, which is exactly the property that makes it a safer candidate for therapy than the pluripotency factors. As Plesa put it, the team worked on the premise that over-expressing a single gene with validated rejuvenation outcomes could eventually be advanced into an organ- or tissue-specific gene therapy if combined with the right delivery system.

The decisive test came in living animals. The researchers packaged the SRSF1 gene into a liver-tropic adeno-associated virus, or AAV, a widely used gene delivery vehicle, and treated aged mice. The gene primarily accumulated in the animals’ livers, and the results were remarkable on two fronts. First, the livers themselves showed signs of rejuvenation. Second, and more strikingly, the benefits were systemic: SRSF1-treated animals grew frail more slowly than controls and lived longer, with median lifespan extended by 14 percent. That a single RNA processing factor, delivered mainly to one organ, could slow the aging of the whole organism positions SRSF1 as what the researchers call a geroprotective target, and it hints that rejuvenation programs initiated in one tissue may be communicated and amplified throughout the body.

Exactly how SRSF1 accomplishes its multifaceted effects remains an open and actively pursued question. The protein’s best-known role is that of an RNA splicing factor, one that helps include alternative exon sequences in a subset of mature messenger RNA molecules. These alternatively spliced mRNAs are then translated by ribosomes into proteins with altered functions, effectively allowing one gene to produce a repertoire of protein variants. The team observed a strong trend of alternatively spliced mRNAs following SRSF1 over-expression, but as Plesa acknowledged, they are only just beginning to understand how these splicing changes bring about the multi-faceted rejuvenation program in tissues. Unraveling that mechanism could reveal additional targets and open entirely new avenues for intervention.

For George Church, the Wyss Institute core faculty member and Professor of Genetics at Harvard Medical School who led the study, the work represents a step toward a long-standing ambition: devising clinically useful de-aging strategies by identifying genes that, when engineered for under- or over-expression in aging target tissues, extend human health-span. In his view, aging research is transiting an inflection point where exponential progress in biotechnology is beginning to impact the core aging processes that would otherwise kill 90 percent of us. Significant hurdles remain before SRSF1 could reach the clinic, particularly around delivery and dosing, and further research into its systemic effects is clearly needed. But the study demonstrates something once thought impossible: that a precisely targeted gene, measured against a rigorous transcriptomic yardstick, can turn back key aspects of the aging clock in cells and in a living mammal, without sacrificing what those cells are meant to be.

Subject of Research: Gene expression reprogramming to reverse cellular and organismal aging using the RNA splicing factor SRSF1

Article Title: Reversing age by reprogramming gene expression networks

Article References: Reversing age by reprogramming gene expression networks. (n.d.). Original publication

Image Credits: AI Generated

DOI: Not provided

Keywords: aging, rejuvenation, SRSF1, gene expression, transcriptomic aging clock, Yamanaka factors, cellular senescence, RNA splicing, gene therapy, lifespan extension, machine learning, geroprotection

Alternative splicing occurs in nearly all multiexon human genes, allowing cells to include or skip particular coding segments and thereby generate multiple protein isoforms from a single gene. While the sheer scale of this proteome diversity has long been debated, recent mass spectrometry efforts have confirmed that most well-expressed alternative transcripts do give rise to detectable proteins. What has remained murky is how this diversity translates into function — specifically, how splicing decisions reshape the web of protein-protein interactions and determine subcellular localization. The new study tackles this question by combining network modeling, high-content imaging, machine learning, structural bioinformatics and classical biochemistry into a single integrated framework.

The team began by constructing an interface-resolved map of the human interactome, drawing on curated interaction data from resources including UniProt, DOMINO, IntAct, 3DID and the Eukaryotic Linear Motif database. In this network, every edge represents not just a protein-protein interaction but a specific, experimentally mapped contact surface. By integrating differential splicing data across 75 tissues and cell types, the researchers identified frame-preserving alternative splicing events whose encoded protein regions overlapped at least one mapped interface residue. Roughly 6.5 percent of all annotated interfaces turned out to be subject to splicing regulation, defining a proteome-wide landscape of interface-level variation concentrated at highly connected modular hubs.

Percolation analysis — a technique borrowed from network science in which edges are progressively removed to see how the network fragments — revealed a striking division of labor. The most tissue-specific exons preferentially rewired interactions locally, within functional modules such as individual signaling pathways, without breaking the overall connectivity of the interactome. In contrast, more tissue-wide splicing events, and microexons in particular, were significantly enriched among interfaces that connect distinct functional communities. In other words, microexons tend to sit at the junctions between pathways and complexes, occupying network positions that modulate crosstalk between different cellular processes. Regression modeling confirmed that this intercommunity effect depended on both the degree of tissue regulation and microexon status, suggesting that these tiny exons represent a specialized class of tissue-specific events with a disproportionate influence on how the proteome is organized.

The analysis also showed that tissue-specific splicing preferentially targets multidomain, multifunctional proteins — those built from many distinct binding modules and capable of interacting with proteins, DNA, RNA and lipids. Such proteins appear to tolerate local changes in their binding surfaces without losing their core activities. Crucially, the researchers found that proteins regulated by tissue-specific splicing also showed greater subcellular localization diversity, being found in more cellular compartments than their less-spliced counterparts. This association was strongest among highly modular proteins, hinting that splicing and spatial deployment are mechanistically linked. A computational screen using the protein language model ProtGPS predicted that nearly 28 percent of tested exons would redistribute their host proteins across subcellular compartments — a figure compelling enough to justify direct experimental testing.

That test came in the form of a high-content imaging screen. The team cloned 68 protein isoforms across 32 genes involved in endocytosis and cytoskeletal organization, each pair differing only by the inclusion or exclusion of a single alternative exon, and fused them to the fluorescent marker mCherry. After transfecting the constructs into HeLa cells and imaging them by automated confocal microscopy, the researchers extracted roughly 200 features from each cell’s fluorescence signal and trained machine-learning classifiers to distinguish between isoforms based on localization alone. The result: 38 percent of the 42 isoform pairs tested showed significantly different subcellular distributions, with microexons and longer exons contributing at nearly identical rates. Examples included the membrane-associated proteins ANK2, NUMB and OCRL, whose isoforms displayed graded differences in membrane association and granularity rather than wholesale relocalization.

The standout hit was sorting nexin 2, or SNX2, a multidomain protein involved in retrograde transport and recycling of internalized membrane proteins. Its two isoforms differ by a four-residue microexon encoding the sequence EIEE, inserted directly into the BAR domain — a coiled-coil structure that mediates lipid binding, dimerization and assembly into higher-order protein coats. AlphaFold2 modeling predicted that the insertion adds a single helical turn to the domain’s α3 helix, preserving the overall fold while making the surface more negatively charged and repositioning flanking charged residues, particularly arginine 451 and glutamate 452. The isoform without the microexon formed punctate, vesicular structures and aggregates at high expression, while the microexon-containing isoform showed a more diffuse cytoplasmic distribution — a difference that persisted even when untagged isoforms were expressed at near-endogenous levels in engineered rescue cell lines.

The most surprising finding came from mutagenesis. The team generated 18 SNX2 mutants and found that the presence or absence of the four-residue insertion, rather than the precise identity of its amino acids, was the main determinant of localization behavior. Even mutants with drastically altered exon sequences clustered with the microexon-containing isoform. Conversely, progressively mutating the flanking arginine 451 from positively charged to neutral to negative gradually shifted the exon-less construct toward the microexon-containing phenotype. Interaction assays reinforced the story: both isoforms formed canonical SNX-BAR complexes, but the microexon-containing isoform bound the insulin receptor roughly twice as strongly, and this enhanced binding followed the insertion rather than the exon’s composition. Together, these results demonstrate that a microexon can act as a structural spacer, physically displacing pre-existing charged residues and retuning the electrostatic landscape of an interaction interface without destroying the protein fold.

The broader implications are considerable. The study establishes a dual-mode model of splicing regulation: longer exons tend to act as digital switches that add or remove entire interaction modules within pathways, while microexons operate as analog fine-tuners at intercommunity interfaces, subtly adjusting electrostatics and residue positioning to modulate both localization and partner specificity. Because splicing-driven localization changes appear to be graded rather than binary, single exons can dial protein deployment up or down without wholesale relocalization — a mechanism with echoes in SRC kinase, where a microexon in the SH3 domain switches its peptide-binding preference, and in the gastric epithelium-specific exon of MLCK1, whose isoform-specific interactions are relevant to inflammatory bowel disease. The authors caution that their analysis is limited to frame-preserving events overlapping annotated interfaces, and that imaging assays relied primarily on tagged overexpression, though the SNX2 rescue experiments mitigated this concern. Even so, the message is clear: to understand where a protein lives and whom it talks to, scientists may need to look not just at the gene, but at the tiny splicing decisions that sculpt its interfaces one residue at a time.

Subject of Research: How alternative splicing and microexons reshape protein interaction interfaces and subcellular localization

Article Title: Alternative splicing fine-tunes modular protein interfaces to control protein localization

Article References: Kjer-Hansen, P., Pazaky, K., Kavanagh, D., King, H. E., O’Connell, S., Santos-Rodriguez, G., Grootveld, A. K., Vieira, H. G. S., Berry, S., Fernandez-Chamorro, J., & Weatheritt, R. J. (2026). Alternative splicing fine-tunes modular protein interfaces to control protein localization. Nature Structural & Molecular Biology. https://doi.org/10.1038/s41594-026-01875-8

Image Credits: AI Generated

DOI: 10.1038/s41594-026-01875-8

Keywords: alternative splicing, microexons, protein localization, protein-protein interactions, proteome organization, SNX2, BAR domain, high-content imaging, AlphaFold2, electrostatics, interactome, RNA splicing

Poison exons are a striking example of evolutionary ingenuity. They are highly conserved exon sequences whose inclusion in a mature transcript introduces a premature termination codon, an early stop signal that the cell recognizes as a mistake. Rather than translating the flawed message into a truncated and potentially harmful protein, the cell destroys the transcript through a quality-control pathway known as nonsense-mediated decay, or NMD. In effect, a poison exon acts as a molecular volume knob: when it is spliced in, the gene is silenced; when it is spliced out, the gene’s protein is produced. Because this mechanism allows cells to fine-tune protein levels rapidly and reversibly, without changing the underlying DNA, poison exons have long been suspected to play a major role in post-transcriptional regulation. What has been missing is a systematic, transcriptome-wide inventory of where they are and what they do.

The new study addresses that gap with unusual breadth. The researchers performed a comparative analysis of 954 eukaryotic transcriptomes spanning a wide range of species, asking how frequently each organism produces RNA isoforms targeted by nonsense-mediated decay. The answer was unambiguous: Homo sapiens stands out as the species with the highest enrichment of NMD-targeted isoforms, suggesting that this form of regulation became especially elaborate in the human lineage. Building on that observation, the team systematically predicted and annotated splicing events capable of generating premature termination codons across the human genome, cataloging 9,814 poison exons in total — a dramatic expansion over the fragmentary annotations that existed before.

With the catalog in hand, the researchers turned to two of the most valuable resources in human genomics: GTEx, which profiles gene expression across dozens of tissues from hundreds of donors, and BrainSpan, which charts transcriptomic changes across human brain development from prenatal stages into adulthood. By mining RNA sequencing data from these repositories, they mapped how poison exon inclusion varies across the body and across the lifespan. The results were striking. The team identified 83 poison exons found uniquely in the human brain, 973 that show brain-specific differential splicing compared with other tissues, and 1,284 whose splicing changes significantly during brain development. In other words, a substantial fraction of the genome’s poison exon repertoire is deployed in neural tissue, and its deployment shifts as the brain matures — a pattern consistent with a regulatory system tailored to the demanding and precisely timed business of building and maintaining neurons.

What kinds of genes carry these brain-relevant poison exons? The functional and pathway enrichment analyses performed by the team point toward processes at the heart of neural biology, including synaptic function and neuronal development, and toward disease categories dominated by neurological conditions. That connection moved from correlation to mechanism when the researchers cross-referenced their poison exon map with ClinVar, a public archive of clinically observed genetic variants, and with SpliceAI, a deep-learning tool that predicts how DNA variants alter splicing patterns. The screen revealed 1,625 pathogenic variants associated with neurological disorders that are predicted to disrupt the splicing of 743 poison exons. Each such variant, in principle, could tilt a cellular volume knob in the wrong direction — forcing a poison exon into transcripts that should exclude it, or removing one from transcripts that need it, thereby raising or lowering the level of a critical neural protein.

Crucially, the team did not stop at prediction. They functionally validated the impact of a subset of these variants using CRISPR prime editing in human cells, a precision genome-engineering technique that can introduce exact genetic changes without making double-strand breaks in DNA. The experiments confirmed that the predicted splicing defects were real: engineered variants changed poison exon inclusion in the predicted direction, providing direct experimental support for the computational pipeline and for the broader idea that poison exon mis-splicing is a genuine disease mechanism rather than a bioinformatic curiosity.

The most detailed case study centered on a variant with a known clinical consequence. The intronic NDUFAF6 c.420+784C>T variant is associated with Leigh syndrome, a devastating mitochondrial disorder that typically strikes infants and progressively damages the brain and other energy-hungry organs. NDUFAF6 encodes an assembly factor required for building mitochondrial complex I, the molecular machine that generates much of the cell’s energy supply. Using induced pluripotent stem cell-derived neurons — i3N neurons, a rapid differentiation system that produces neuronal-like cells from patient or engineered stem cells — the researchers showed that the variant causes increased inclusion of a poison exon in the NDUFAF6 transcript. The consequence was a significant reduction in NDUFAF6 protein levels, and downstream of that, impaired mitochondrial membrane potential compared with control neurons. The chain of causation was thus traced end to end: a single DNA letter change, deep inside an intron, rewires splicing to insert a premature stop codon, the cell destroys the transcript, protein levels fall, and mitochondria malfunction — the cellular signature of Leigh syndrome.

The implications of this work extend well beyond a single gene or disease. Because poison exons act as tunable regulators of protein abundance, they represent an unusually attractive class of therapeutic targets. Antisense oligonucleotides — short synthetic RNA molecules that can be designed to block or promote specific splicing events — are already approved for other splicing-based disorders, and the study’s authors note that their own patent portfolio includes work on RNA splicing modulation. A poison exon that is aberrantly included in a patient’s neurons could, in principle, be skipped by a designed oligonucleotide, restoring normal protein production without ever touching the genome. Conversely, prime editing or base editing strategies could correct the underlying splicing variants at their source, an approach the team has explored for familial dysautonomia, another splicing-driven neurological disease. The new catalog of 9,814 poison exons, together with the list of 743 whose splicing is predicted to be disrupted by pathogenic variants, effectively hands the therapeutic community a prioritized target list.

The study also reframes how scientists should think about the enormous fraction of disease-causing mutations that lie outside protein-coding regions. Variants in introns and other non-coding DNA have often been difficult to interpret, but the NDUFAF6 case demonstrates that a deep intronic change can be every bit as pathogenic as a mutation in a coding sequence — provided one knows to look for its effect on splicing. Tools like SpliceAI, applied systematically as they were here to more than 236,000 ClinVar variants, can surface such effects at scale, and the authors compared SpliceAI’s performance against another splicing predictor, Pangolin, to strengthen their calls. As diagnostic sequencing expands, incorporating poison exon-aware splicing prediction into variant interpretation could resolve cases that currently go undiagnosed, particularly in neurodevelopmental and neurodegenerative conditions where the genetic basis remains elusive for many patients.

There are caveats and open questions, as with any ambitious mapping effort. The study’s tissue and developmental analyses rest on bulk RNA sequencing data, which averages signals across the many cell types of the brain, and the functional validations, while rigorous, cover a subset of the predicted events. The authors acknowledge that the field’s understanding of poison exon regulation — which splicing factors control which switches, and in response to what signals — is still in its infancy. Yet the scale of the new resource, the evolutionary signal that humans are the most NMD-enriched species examined, and the demonstration that a single poison exon mis-splicing event can recapitulate the mitochondrial pathology of Leigh syndrome together make a compelling case. Poison exons, once a footnote of RNA biology, now look like a central chapter in the story of how the human brain regulates its genes — and a promising frontier for treating the diseases that arise when that regulation fails.

Subject of Research: Poison exon splicing and its role in gene regulation and neurological disorders in the human brain

Article Title: Poison exon splicing in the human brain provides a new paradigm for understanding and targeting neurological disorders

Article References: Pigini, P., Xu, H., Ji, Y., Lindmeier, H., Saltzman, H. R., Shull, H., Yun, S., Alves, C. R. R., Walker, M. A., Silva, M. C., Gao, D., & Morini, E. (2026). Poison exon splicing in the human brain provides a new paradigm for understanding and targeting neurological disorders. Genome Biology. https://doi.org/10.1186/s13059-026-04292-8

Image Credits: AI Generated

DOI: 10.1186/s13059-026-04292-8

Keywords: poison exons, alternative splicing, nonsense-mediated decay, RNA splicing, human brain, neurological disorders, Leigh syndrome, NDUFAF6, SpliceAI, CRISPR prime editing, GTEx, BrainSpan

The clinical spectrum of myotonic disorders is broad. Myotonic dystrophy type 1, or DM1, is the most common of them, with prevalence estimates based on clinical diagnosis ranging from one in six to ten thousand, although genetic screening data suggest as many as one in 2,100 people may be affected. DM1 results from an unstable expansion of CTG repeats in the DMPK gene on chromosome 19. The expanded transcripts exert a toxic gain of function, sequestering RNA-binding proteins and disrupting alternative splicing across the genome, which explains why the disease touches so many organ systems. Patients may develop progressive muscle wasting and weakness, cardiac conduction disease and cardiomyopathy, respiratory failure, cataracts, diabetes, thyroid dysfunction and cognitive impairment. Presentation varies enormously: some individuals live nearly normal lives and remain undiagnosed well into adulthood, while others lose ambulation and face shortened life expectancy from cardiorespiratory complications. Myotonic dystrophy type 2, caused by a CCTG expansion in the CNBP gene on chromosome 3, shares the same RNA-mediated spliceopathy mechanism but tends to produce a milder, proximal myopathy without the congenital forms or genetic anticipation seen in DM1.

Distinct from the dystrophies are the non-dystrophic myotonias, pure skeletal muscle channelopathies caused by variants in ion channel genes, with no systemic involvement and a normal life expectancy. Myotonia congenita, the most common with a prevalence of roughly two to seven per 100,000, stems from variants in CLCN1, the gene encoding the ClC-1 voltage-gated chloride channel essential for membrane repolarisation. It is the same channel whose function is secondarily disrupted in myotonic dystrophy. Paramyotonia congenita and sodium channel myotonia are allelic autosomal dominant disorders of SCN4A, the gene for the Nav1.4 sodium channel that generates the action potentials driving contraction. Paramyotonia is notorious for worsening with cold and repeated activity, and can be accompanied by episodic paralysis, while sodium channel myotonia may show both warm-up and paradoxical worsening. For many patients, pain and fatigue are as troublesome as the stiffness itself, and the visible normality of their appearance can make the condition a hidden disability.

The therapeutic mainstay for myotonia has long been sodium channel blockade. In paramyotonia and sodium channel myotonia the mechanism is direct, since the underlying SCN4A variants confer a gain of channel function that the drugs inhibit. In myotonia congenita and the dystrophies the effect is indirect: reducing persistent sodium current partially compensates for impaired chloride-mediated repolarisation. Mexiletine emerged as first-line therapy on the strength of clinical impression, and in 2012 the first randomised controlled trial confirmed its efficacy in non-dystrophic myotonia, with subsequent studies, including aggregated N-of-1 trials, consolidating the evidence. Secondary outcomes consistently showed benefits extending to quality of life, pain, fatigue, independence and emotional well-being. Lamotrigine joined the arsenal in 2017 when a phase 2 crossover trial in 22 patients demonstrated efficacy on the myotonia behaviour score, making these two drugs the only anti-myotonic agents with randomised trial evidence. A head-to-head phase 3 trial failed to show lamotrigine was non-inferior to mexiletine, but it still delivered considerable benefit, giving clinicians two credible options.

Both drugs have also shown efficacy in DM1, with favourable cardiac safety profiles in trials, though these studies were small, short and potentially subject to selection bias in a population where cardiac conduction defects are common. Evidence in DM2 remains far thinner, with no dedicated large randomised trials, forcing treatment strategies to be extrapolated from other populations. Cardiac caution has historically shadowed mexiletine because of its potential pro-arrhythmic properties, yet neither the trials nor 302.4 years of real-world follow-up in non-dystrophic myotonia demonstrated significant electrocardiographic changes, and observational data in myotonic dystrophy show no safety signal on conduction parameters. The FDA has issued a warning on lamotrigine based on in vitro class 1B sodium channel blocker activity, but this has not been replicated by other regulators, including the European Medicines Agency, and has not translated into observable effects on human cardiac conduction. A joint ILAE/AES task force now recommends baseline electrocardiography only for those over 60 or with multiple cardiovascular risk factors, with specialist review mandatory for known cardiac disease. Clinicians must also weigh the rare but serious risk of Stevens-Johnson syndrome with lamotrigine, which a 55-year review of the FDA adverse event database found accounted for nearly ten percent of reported cases.

Practical considerations are also reshaping prescribing. Mexiletine, licensed as Namuscla for adults with non-dystrophic myotonia in several countries and used off-label in children and in myotonic dystrophy, typically requires dosing up to three times daily, which can undermine adherence. Prolonged-release once-daily formulations are now in phase 3 trials: the HERCULES study in DM1 and DM2 and the ACHILLES study in non-dystrophic myotonia. Meanwhile, basic science continues to probe alternative targets. No specific chloride channel activators exist, but intriguing work has shown that niflumic acid, which acutely blocks the ClC-1 channel in transfected cells, paradoxically acts as a pharmacological chaperone that increases channel protein expression when applied over 24 hours. Potassium channel openers such as retigabine, withdrawn from the market in 2017 over blue pigmentation concerns, have inspired next-generation compounds in development.

The most dramatic shift, however, is in DM1, where an era of molecularly targeted clinical trials is underway. Several companies are developing therapies designed to reduce the mutant DMPK transcript or to prevent the sequestration of muscleblind-like protein 1, the key splicing regulator whose loss drives the downstream transcriptional chaos. Delivery strategies range from naked oligonucleotides to targeted conjugates and adeno-associated virus vectors, with studies progressing from early-phase work to phase 3. The most advanced candidate is del-desiran, an antibody-oligonucleotide conjugate that hijacks the transferrin receptor to ferry the drug into muscle. In the phase 2 MARINA trial it demonstrated target engagement and amelioration of aberrant alternative splicing in some patients, a proof of principle that has electrified the field. None of these approaches is curative, and the extent of achievable molecular and clinical correction remains uncertain, but they represent the first credible assault on the underlying pathology rather than its symptoms.

Translational challenges loom large. Many trials use video hand opening time as the primary endpoint, a measure that captures skeletal muscle excitability and likely reflects modulation of MBNL-dependent mis-splicing of ion channel transcripts, making it a useful proof-of-mechanism marker, but its relevance to broader clinical benefit in a multisystem disease is debated. Effects on the heart and brain may not be established for years and will depend on post-marketing surveillance. Delivery poses further difficulties: repeated intravenous infusions at six- to eight-week intervals demand substantial healthcare infrastructure and may limit scalability and central nervous system penetration. Alongside the genetic approaches, repurposed small molecules are advancing. Metformin showed signals of efficacy on the six-minute walk test in the MYOMET phase 2 study, though the primary endpoint was missed in the intention-to-treat population, and the larger phase 3 METFORMYO trial is now underway with the MFM-32 as its primary measure. Tideglusib, a GSK3-beta inhibitor tested in congenital and childhood-onset DM1, showed signals in cognitive and neuromuscular ratings without significant safety concerns, and a phase 2/3 study in children is recruiting. Erythromycin, which modulates MBNL-dependent splicing preclinically, was well tolerated in a phase 2 trial with promising improvements in splicing biomarkers and creatine kinase levels.

Symptomatic care continues to evolve in parallel. Excessive daytime sleepiness affects the majority of people with DM1, yet randomised evidence for psychostimulants such as modafinil remains thin. A phase 2 trial of pitolisant in 30 participants suggested improvements in subjective sleepiness but was not powered for statistical significance, and a small study of intravenous flumazenil found no benefit over placebo. The overall picture that emerges from the review is not one of replacement but of layering: mechanism-based therapies are being built on top of a symptomatic framework that already works reasonably well for myotonia, even as it leaves progressive weakness and multisystem degeneration unaddressed. The recurring theme, the authors note, is the gap between molecular target engagement and clinically meaningful benefit, a gap that applies equally to established drugs and to the new genetic agents. Whether the emerging therapies will ultimately change disease trajectory remains uncertain, but for patients who have waited decades for anything more than symptomatic relief, the pipeline now offers genuine hope, and clinicians are being urged to prepare for a practice landscape that may look radically different within a few years.

Subject of Research: Treatment advances for myotonia in myotonic dystrophy and non-dystrophic muscle channelopathies

Article Title: Treatment updates in myotonic disorders

Article References: Matthews, E., Specterman, M. J., & Mul, K. (2026). Treatment updates in myotonic disorders. Journal of Neurology, 273(10), Article 562. https://doi.org/10.1007/s00415-026-14073-9

Image Credits: AI Generated

DOI: 10.1007/s00415-026-14073-9

Keywords: myotonia, myotonic dystrophy type 1, myotonia congenita, sodium channel blockers, mexiletine, lamotrigine, RNA splicing, oligonucleotide therapy, clinical trials, muscle channelopathies, DMPK gene, disease-modifying therapy

Protein S is a cofactor for the activated protein C system, one of the body’s principal brakes on blood coagulation. When PROS1 function is impaired, the clotting cascade runs unchecked, and affected individuals face elevated risks of deep vein thrombosis and pulmonary embolism. Genetic testing for Protein S deficiency routinely encounters variants of uncertain significance, or VUS, and synonymous changes are among the most frequently dismissed, typically labeled benign because the protein sequence appears intact. The new study set out to test whether that dismissal is justified, systematically evaluating fourteen synonymous PROS1 variants with an unusually comprehensive experimental toolkit.

The investigators combined computational prediction with laboratory validation. In silico analyses assessed each variant’s likely impact on pre-mRNA splicing, messenger RNA stability, and codon usage, the preference for particular synonymous codons that can influence how efficiently ribosomes translate a transcript. The team then moved to bench experiments, deploying minigene splicing assays to see how each variant altered RNA processing in a controlled cellular setting, measuring mRNA decay rates to quantify transcript stability, and running protein expression and anticoagulant activity assays to determine the downstream functional consequences.

The results were unambiguous: these silent mutations are anything but silent. Six of the fourteen variants, or 42.9 percent, caused aberrant pre-mRNA splicing, meaning the cellular machinery misprocessed the RNA intermediate and produced faulty transcripts. Two variants, 14.3 percent, reduced mRNA stability, hastening the degradation of the PROS1 message before enough Protein S could be made. Another two variants, also 14.3 percent, impaired translational efficiency, leaving ribosomes less able to convert the message into functional protein. In every affected case, the molecular defect cascaded into decreased Protein S expression and diminished anticoagulant activity in the relevant assays.

The clinical significance of these findings was reinforced by data from three additional patients carrying spliceogenic PROS1 variants. Each of these individuals exhibited reduced Protein S levels and thrombotic manifestations that matched the functional defects identified experimentally, providing a genotype-phenotype correlation that links laboratory mechanism to real-world disease. This convergence of molecular and clinical evidence is precisely what variant interpretation guidelines have long demanded but rarely received for synonymous changes.

That convergence had immediate diagnostic consequences. By integrating the multi-layer functional evidence with clinical data, the researchers were able to reclassify several variants under the American College of Medical Genetics and Genomics and Association for Molecular Pathology framework, the standard rubric for assessing pathogenicity. Variants previously parked in the VUS category were moved to likely pathogenic or, in some cases, benign, sharpening the molecular diagnosis of Protein S deficiency and giving clinicians firmer ground for counseling patients and their families about thrombotic risk.

Perhaps the most forward-looking part of the study is its therapeutic proof of concept. Rather than stopping at diagnosis, the team pursued mechanism-guided RNA correction. For selected spliceogenic variants, they engineered modified U1 small nuclear RNAs, components of the spliceosome that can be tailored to recognize mutated splice sites, and antisense U7 snRNAs, which can block aberrant splice sites or redirect the splicing machinery. Delivered into cells, these engineered molecules partially restored normal splicing patterns for the targeted variants, demonstrating that the molecular defects are not only identifiable but potentially correctable.

The implications extend well beyond a single gene. Synonymous variants populate every protein-coding gene in the genome, and growing evidence indicates they can contribute to disease through splicing disruption, mRNA destabilization, altered microRNA binding, and impaired translation. Yet in routine clinical reporting they are still too often waved through as benign. The PROS1 study offers a template for how to interrogate them properly: pair computational screening with minigene assays, mRNA measurements, and protein-level functional readouts, then anchor the findings in patient phenotype data. Applied more broadly, such pipelines could rescue meaningful diagnoses from the VUS backlog that clogs modern genomics.

For patients with inherited thrombophilia, the therapeutic angle is particularly compelling. Current management of Protein S deficiency relies on anticoagulant drugs and vigilance rather than correction of the underlying defect. RNA-based splice correction, already being explored in other genetic diseases, offers a strategy that is variant-specific yet conceptually scalable: once a patient’s spliceogenic variant is defined, a tailored snRNA could in principle be designed to fix it. The partial restoration achieved in this study is an early step, and translating engineered snRNAs from cell culture to safe, effective human therapy will require substantial further development, but the feasibility argument has now been made for PROS1-related thrombosis.

The study also carries a cautionary message for genetic counseling. A synonymous PROS1 variant reported as benign today could, in a family with unexplained thrombosis, be the culprit. As functional evidence accumulates, guidelines will need to keep pace, and laboratories may need to treat synonymous variants near splice junctions or in conserved codon contexts with greater suspicion. What this research makes clear is that the genome’s apparent redundancy conceals layers of regulation, splicing, transcript stability, and translation, that mutation can disturb without changing a single amino acid. In the case of PROS1, listening to those silent signals revealed both hidden causes of a dangerous clotting disorder and a credible route toward fixing them with RNA.

Subject of Research: Functional and clinical characterization of synonymous PROS1 variants causing Protein S deficiency and their RNA-based splicing correction

Article Title: Comprehensive molecular and clinical characterization of synonymous PROS1 variants: from molecular mechanisms to RNA-based splicing correction

Article References: Zhang, H., Su, X., Yu, Q., Pan, B., Ma, D., Francesco, B., Guo, W., Wang, B., Balestra, D., & Zhao, Y. (2026). Comprehensive molecular and clinical characterization of synonymous PROS1 variants: from molecular mechanisms to RNA-based splicing correction. Journal of Translational Medicine. https://doi.org/10.1186/s12967-026-09005-0

Image Credits: AI Generated

DOI: 10.1186/s12967-026-09005-0

Keywords: PROS1, Protein S deficiency, synonymous variants, RNA splicing, thrombophilia, U1 snRNA, U7 snRNA, ACMG/AMP classification, mRNA stability, variant interpretation, RNA therapeutics, minigene assay

Lsm8 is the defining subunit of the nuclear Lsm2-8 complex, a heptameric ring of Like-Sm proteins that binds the 3-prime end of U6 small nuclear RNA, the catalytic core of the spliceosome. The spliceosome is the macromolecular machine that removes introns from pre-messenger RNA, and without properly assembled Lsm2-8, U6 is left unprotected and splicing cycles falter. Sequence analysis showed that the Fusarium Lsm8 protein shares roughly half its identity with its yeast counterpart and about 65 percent with the human version, underscoring how ancient this module is. Although Lsm8 lacks a predicted nuclear localization signal, a fluorescent Lsm8-GFP fusion co-localized precisely with a histone marker in fungal nuclei, confirming where the protein operates.

To map the complex’s architecture, the team deployed a battery of interaction assays. Yeast two-hybrid tests revealed direct contacts between Lsm8 and Lsm2 and Lsm3, bimolecular fluorescence complementation captured a nuclear interaction between Lsm8 and Lsm4, and co-immunoprecipitation validated all of these associations in living fungal cells. Most decisively, affinity purification followed by mass spectrometry, using Lsm8-GFP as bait, co-purified all six remaining Lsm subunits. The picture that emerged is of Lsm8 as a central architectural keystone. When the researchers deleted the LSM8 gene, GFP-tagged Lsm2, Lsm3 and Lsm4 abandoned the nucleus entirely and diffused throughout the cytoplasm, demonstrating that Lsm8 is indispensable for both assembling the ring and escorting it to its workplace.

The consequences of losing this keystone were dramatic. Deletion mutants grew slowly on every medium tested, from rich potato dextrose agar to minimal medium. Transcriptome sequencing revealed massive reprogramming: 1,710 genes were significantly upregulated and 1,796 downregulated. The upregulated set was enriched in ribosome biogenesis, spliceosome function and RNA degradation, which the authors interpret as a compensatory feedback response to the missing splicing machinery. The downregulated genes clustered in carbon and nitrogen metabolism, including glycolysis and the pentose phosphate pathway, providing a molecular explanation for the growth collapse. Quantitative PCR confirmed the sequencing results for splicing factors such as PRP4 and PRP5, degradation factors such as RRP6 and XRN2, and glycolytic genes such as FBA1 and ENO1.

The most striking defect, however, lay in splicing itself. Across 13,982 detected introns, the median intron retention rate jumped from 0.011 in the wild type to 0.089 in the mutant, a highly significant eight-fold increase. In total, 2,344 introns from 1,821 genes showed significantly elevated retention, while only 45 introns became better spliced. Crucially, most of the affected genes, 1,270 of them, showed no change in overall transcript abundance, meaning the damage was purely post-transcriptional: transcripts were made normally but never spliced correctly. Retained introns disrupt reading frames, producing truncated or non-functional proteins, or triggering nonsense-mediated decay. The affected genes were enriched in chromatin remodeling, RNA polymerase activity, nucleocytoplasmic transport and DNA repair, processes essential to cellular integrity.

The splicing failures mapped directly onto the fungus’s environmental vulnerabilities. When challenged with a panel of eight stress agents, the mutant proved hypersensitive to all of them, with the strongest effects under osmotic stress from salt and the fungicide fludioxonil, which works by hyperactivating the osmotic stress pathway. The team traced this to the high osmolarity glycerol, or HOG, MAPK cascade. HOG1 carries eight introns, and nearly all of them were inefficiently spliced in the mutant, with defects worsening under stress. Total HOG1 mRNA levels were unchanged, but Hog1 protein levels dropped significantly, showing that the defect lies in protein production rather than transcription. Intriguingly, the residual Hog1 that remained was hyperphosphorylated, and intracellular glycerol accumulated to roughly three times wild-type levels, suggesting distorted pathway feedback. The downstream transcription factor ATF1 also showed splicing abnormalities.

Reproduction fared no better. The mutant produced fewer conidia, the asexual spores that spread infection, and those spores were shorter and abnormally septated. Sexual development was abolished outright: on carrot agar under black light, the mutant formed no perithecia at all, the fruiting bodies that generate overwintering ascospores. The molecular culprits were again splicing defects, this time in two developmental regulators. GPA1, encoding a heterotrimeric G protein alpha subunit, retained all three of its introns at elevated rates, and STE12, a transcription factor essential for sexual reproduction, retained both of its introns. As with HOG1, total mRNA levels were largely unaffected, reinforcing the theme that Lsm8’s influence operates after transcription.

Virulence and mycotoxin synthesis collapsed in parallel. Infection assays on wheat heads, wheat coleoptiles and corn silks showed the mutant was nearly nonpathogenic, and deoxynivalenol production fell sharply. The TRI gene cluster that manufactures the toxin was hit twice: key genes including TRI1, TRI4, TRI5, TRI6, TRI10 and TRI101 were transcriptionally downregulated, and the splicing efficiency of TRI1, TRI4 and TRI5 transcripts was significantly reduced. Microscopy of a Tri1-GFP reporter delivered perhaps the most visually compelling result: in the wild type, Tri1 aggregates into the spherical toxisomes, specialized compartments where deoxynivalenol is synthesized, but in the mutant almost no toxisomes formed and Tri1-GFP protein levels plummeted. Lsm8 thus guards the fungus’s chemical arsenal at every regulatory level simultaneously.

Finally, the study answered a long-standing question about what happens to all those defective transcripts. In eukaryotes, aberrant RNAs are normally cleared by nonsense-mediated decay, the RNA exosome, which degrades transcripts in the 3-prime to 5-prime direction, or by Xrn enzymes working in the opposite direction. Mass spectrometry showed that Lsm8 physically interacts with core exosome subunits including Rrp45, Rrp4 and Dis3, and the mutant compensated by upregulating exosome components. Genetic dissection proved decisive: intron-retained HOG1 transcripts accumulated massively in an exosome-subunit deletion mutant and even more in an Lsm8-exosome double mutant, while accumulation in an Xrn1 mutant was comparatively modest. The exosome, the authors conclude, is the predominant degrader of intron-retained transcripts arising from Lsm2-8 dysfunction, with Xrn1 playing a supporting role. Because both the Lsm2-8 complex and the exosome are conserved across eukaryotes, from yeast and plants to worms and humans, this coupled splicing-and-surveillance module appears to be a fundamental feature of eukaryotic biology. In Candida albicans, a human fungal pathogen, Lsm loss already impairs filamentation and pathogenicity, suggesting the Fusarium findings generalize. Targeting this conserved module, the researchers argue, could yield antifungal strategies that strike at core RNA-processing machinery shared by diverse pathogens, simultaneously curbing crop disease and mycotoxin contamination while sparing the host, whose own cells process RNA through homologous but distinct regulatory contexts.

Subject of Research: RNA splicing fidelity and the Lsm8-exosome surveillance module in fungal stress adaptation and virulence

Article Title: A conserved Lsm8–exosome module maintains RNA splicing fidelity to control fungal stress adaptation and virulence

Article References: Ren, Y., Cheng, H., Han, X., Guo, M., Xu, C., Yan, J., Ge, Z., Ma, Z., & Chen, Y. (2026). A conserved Lsm8–exosome module maintains RNA splicing fidelity to control fungal stress adaptation and virulence. Stress Biology, 6(1), Article 14. https://doi.org/10.1007/s44154-026-00285-6

Image Credits: AI Generated

DOI: 10.1007/s44154-026-00285-6

Keywords: Fusarium graminearum, Lsm8, Lsm2-8 complex, RNA splicing, intron retention, RNA exosome, deoxynivalenol, mycotoxin biosynthesis, HOG-MAPK pathway, fungal virulence, post-transcriptional regulation, antifungal targets