Rare genetic disorders affect more than 300 million people worldwide, yet for roughly 95 percent of them there is no specific treatment. A substantial share of these conditions arises from haploinsufficiency, a situation in which a person retains only one working copy of a gene and the protein made from that single copy is not enough for normal development and physiology. The obvious therapeutic goal is to coax the surviving healthy allele to produce more protein, but safely turning up gene output has proved remarkably difficult. A team of researchers led from the University of Oxford now reports in Genome Medicine a general strategy that could change that picture: rather than editing DNA or flooding cells with extra gene copies, they propose to remove a hidden brake built into the mRNA itself by rewiring how the message is spliced.
The brake in question sits in the 5ʹ untranslated region, the stretch of RNA that precedes the protein-coding sequence of a transcript. Although it does not encode protein, this region exerts powerful control over how efficiently ribosomes translate the main message. One of its most potent repressive elements is the upstream open reading frame, or uORF, a short alternative reading frame that begins at an upstream start codon and diverts ribosomes away from the true protein. When a ribosome initiates at a uORF and terminates before reaching the main coding sequence, that translation event is wasted. Genes carrying strong uORFs therefore tend to make less protein than their mRNA abundance would predict, and in a haploinsufficient disease that shortfall can tip an individual over the threshold of clinical disease.
Earlier proposals for exploiting this biology focused on steric-block antisense oligonucleotides, synthetic DNA-like molecules that bind to the uORF start codon and physically obstruct ribosome initiation. The approach has shown promise for a handful of specific genes, but its broad applicability has been debated, because the geometry of each uORF differs and blocking initiation is not always feasible or effective. The Oxford-led team, working with colleagues at the International Centre for Genetic Engineering and Biotechnology in Trieste, the University of Exeter and industry partners, pursued a different tactic. Instead of masking the uORF, they asked whether the exon that contains it could be spliced out of the mature mRNA altogether, converting an inhibitory 5ʹUTR into a shorter, permissive one through the cell’s own RNA processing machinery.
To test how widely such an approach might apply, the researchers systematically screened human transcript annotations. Using MANE transcript definitions, the matched annotations agreed upon by NCBI and EMBL-EBI as the definitive reference set for each human gene, they catalogued exons located entirely within 5ʹ untranslated regions whose removal would preserve the reading frame and regulatory logic of the transcript. This analysis yielded 2,210 potentially skippable 5ʹUTR exons. The critical next step was to determine which of those exons actually contain functional uORF start codons, since a start codon annotated in the genome is only repressive if ribosomes genuinely engage with it in living cells.
To make that determination, the team mined ribosome profiling data generated from 13 human tissues and cell lines, including brain, heart and skeletal muscle. Ribosome profiling captures snapshots of ribosome positions across the transcriptome, allowing researchers to distinguish start codons that are actively used from those that are silent. Applying this filter, the researchers identified 1,056 skippable 5ʹUTR exons harbouring translated uORF start codons. Crucially, 79 of these exons sit in genes already classified as haploinsufficient monogenic disease genes in expert-curated resources such as ClinGen, the Gene Curation Coalition and Gene2Phenotype. In other words, a defined, immediately clinically relevant target list already exists, and the authors suggest it could serve as a roadmap for precision medicines across dozens of rare disorders.
From that list the team prioritised six candidate exons in genes linked to neurodevelopmental disorders, a therapeutic area where haploinsufficiency is common and where the blood–brain barrier complicates conventional protein replacement. They constructed dual luciferase reporter assays in which the native 5ʹUTR of each target gene drives a measurable enzyme, then compared translation when the candidate exon was removed. For four of the six genes—CTCF, GRIN2B, KRIT1 and TSC1—skipping the target exon significantly boosted downstream protein production, with increases ranging from 1.4-fold to 5.5-fold. That magnitude matters, because many haploinsufficient disorders are thought to respond to even modest restoration of gene dosage, and a twofold increase in protein output would be transformative for conditions in which patients carry essentially half of the normal complement.
A key mechanistic question was whether the benefit came from removing the uORF itself or from other regulatory elements embedded in the skipped exons, such as RNA structures, microRNA sites or RNA-binding protein motifs that might independently suppress translation. To disentangle these effects, the researchers created reporters in which only the uORF start codons were mutated, leaving the rest of the exon sequence intact. Removing the start codons alone increased translation to comparable or even greater levels, between 1.4-fold and 7.9-fold, indicating that the uORF is the dominant repressive element in these exons. For TSC1, the gene mutated in a subset of tuberous sclerosis complex cases, the team went further and showed that multiple uORFs act additively, with each additional upstream reading frame further depressing protein output from the main coding sequence.
The most clinically significant experiment involved splice-switching antisense oligonucleotides, shortened to SSOs. These chemically modified oligonucleotides bind pre-mRNA sequences such as splice donor or acceptor sites and trick the cellular splicing machinery into excluding a chosen exon. The researchers designed SSOs against the prioritised TSC1 5ʹUTR exon and demonstrated that treatment induced the intended exon skipping in cells and up-regulated levels of the endogenous TSC1 protein, produced from the cell’s own genomic copy rather than from a reporter construct. This is the decisive proof of concept: it shows that the strategy works not just on engineered sequences but on the authentic genomic context of a real disease gene, using a drug modality—antisense oligonucleotides—that already has an established clinical track record in spinal muscular atrophy, Duchenne muscular dystrophy and other conditions.
Splice-switching antisense technology brings genuine advantages for rare disease. Because ASOs can be designed rationally from the genomic sequence, a bespoke candidate can be developed quickly for an individual gene or even an individual patient, an approach that has already produced landmark personalised treatments for ultra-rare genetic conditions. The Oxford team’s systematic catalogue of 1,056 uORF-bearing skippable exons effectively converts that bespoke potential into a scalable pipeline: identify the haploinsufficient gene, check whether it carries a skippable 5ʹUTR exon with an active uORF, design an SSO, and titrate protein output back toward normal. The authors argue that their findings support the broad application of 5ʹUTR exon skipping as a general therapeutic mechanism for upregulating protein production from clinically relevant haploinsufficient genes.
Important caveats remain before patients benefit. The four of six prioritised exons that did not respond uniformly remind the field that uORF architecture varies, and that some 5ʹUTR exons may contain activating elements whose loss could be harmful. Delivery to the brain and other tissues, dose control, and the safety of chronically boosting dosage of tumour-suppressor-class genes such as TSC1 and CTCF will all require careful preclinical and clinical evaluation. The translational potential has nonetheless attracted commercial interest: several of the authors hold patents on uORF-targeting technologies and exon-skipping approaches licensed to a University of Oxford spin-out, and the work draws on genomic data from hundreds of thousands of participants in the UK’s National Genomic Research Library. If the approach clears those hurdles, the humble untranslated region—a stretch of RNA long treated as a footnote to the genetic code—may become one of the most promising drug targets in rare disease medicine.
Subject of Research: Using splice-switching antisense oligonucleotides to skip uORF-containing 5ʹ untranslated region exons and upregulate protein expression from haploinsufficient disease genes.
Article Title: Modulating splicing in 5ʹ untranslated regions to treat rare haploinsufficient disease
Article References: Beer Wells, E. S., De Conti, L., Kim, H. C., Rohani, N., Chundru, K., Svrzikapa, N., McClorey, G., Watts, L. M., Dawes, R., Chen, Y., Martin-Geary, A. C., Griffiths, M. J., Scott, S., Bamford, R. A., Wood, M. J., Roberts, T. C., Mill, J., Wright, C. F., Baralle, M., … Whiffin, N. (2026). Modulating splicing in 5ʹ untranslated regions to treat rare haploinsufficient disease. Genome Medicine. https://doi.org/10.1186/s13073-026-01773-0
Image Credits: AI Generated
DOI: 10.1186/s13073-026-01773-0
Keywords: rare disease, haploinsufficiency, antisense oligonucleotides, 5ʹ untranslated region, upstream open reading frames, splicing, therapeutic upregulation, TSC1, CTCF, GRIN2B, neurodevelopmental disorders, Genome Medicine
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Juliet Wilcox. (September 20, 2026). Hidden RNA Switches Offer a New Way to Boost Genes in Rare Disease. Scienmag. https://scienmag.com/hidden-rna-switches-offer-a-new-way-to-boost-genes-in-rare-disease/
Juliet Wilcox. “Hidden RNA Switches Offer a New Way to Boost Genes in Rare Disease.” Scienmag, 20 September 2026, https://scienmag.com/hidden-rna-switches-offer-a-new-way-to-boost-genes-in-rare-disease/. Accessed 20 September 2026.
Juliet Wilcox. “Hidden RNA Switches Offer a New Way to Boost Genes in Rare Disease.” Scienmag. September 20, 2026. https://scienmag.com/hidden-rna-switches-offer-a-new-way-to-boost-genes-in-rare-disease/
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Tags: 5ʹ untranslated regionantisense oligonucleotidesCTCFgene expression modulation without DNA editingGenome MedicineGRIN2Bhaploinsufficiencyhaploinsufficiency treatment approacheshidden RNA switches for gene expressioninnovative genetic medicine techniquesmRNA splicing and translation controlNeurodevelopmental Disordersnovel RNA-based therapies for genetic diseasesovercoming protein deficiency in rare diseasesrare diseaseribosome translation regulation mechanismsRNA gene regulationsplicingtargeting untranslated regions of mRNA for therapytherapeutic strategies for rare genetic disorderstherapeutic upregulationTSC1upstream open reading framesupstream open reading frames (uORFs) in gene regulation
