npj Genomic Medicine

Copy number variants (CNV) contribute significantly to the pathogenic variation associated with developmental disorders. CNV detection is often not included in standard exome sequencing (ES) analysis. Complementary methods such as chromosomal microarray are typically offered in diagnostic laboratories to diagnose pathogenic CNV. In this study, we aimed to develop an optimal approach for incorporating CNV detection within our ES analysis process for the Deciphering Developmental Disorders in Africa (DDD-Africa) cohort. We analyzed ES data from 505 probands with a developmental disorder, applying a CNV detection approach that assessed data generated using the tools CANOES and XHMM. When available, parental ES data was used to assess inheritance patterns. We confirmed a diagnosis in 42/505 (8,3%) patients with 44 pathogenic CNV identified in the probands. There were 31 deletions and 13 duplications. Among the 27 probands with parental data, all identified CNV were de novo. The addition of CNV analysis to our ES analysis pipeline resulted in an 8.3% increase in diagnostic yield in the DDD-Africa cohort without additional laboratory cost. This approach offers a feasible approach which is likely to reduce analytical cost and is suitable for low- and middle-income countries where funding and resources for genomic medicine initiatives are limited.

Variant databases ClinVar and gnomAD are the backbone of clinical variant interpretation, but their population composition is skewed toward European ancestry. Whether this skew creates systematic classification disadvantages for non-European patients with monogenic diabetes has not been examined at the database level. ClinVar variant_summary (GRCh38, April 2026; 4,421,188 variants) was cross-referenced with gnomAD v4.0 genome data for 17 monogenic diabetes genes. Annotation coverage and variant classification rates were computed stratified by genetic ancestry group (AFR, AMR, EAS, SAS, MID, NFE, FIN, ASJ). Of 14,691 gnomAD variants across the 17 genes, only 29.7% had any ClinVar classification (range: 12.7%-61.3% by gene). Among classified variants, non-Finnish European (NFE) variants had the highest variant of uncertain significance (VUS) rate (32.1%) and the lowest benign/likely benign fraction (41.6%), consistent with a large submission volume without functional follow-up. African-ancestry (AFR) variants showed the second-highest VUS rate (29.2%), not statistically distinguishable from NFE after Bonferroni correction, while all other non-European groups had significantly lower rates (all p < 0.001). GCK showed a pattern inversion - non-European VUS rate (18.5%) exceeding European (15.0%) - consistent with progressive reclassification in European populations absent in non-European cohorts. Annotation coverage and VUS divergence were uncorrelated (r = -0.15, p = 0.57). The primary equity problem is a 70% annotation gap combined with a non-European curation deficit, not a simple VUS excess. Ancestry-stratified evaluation of ClinGen Variant Curation Expert Panel (VCEP) criteria performance is warranted across disease domains.

Autism shows a consistent sex bias, yet how sex shapes de novo variant (DNV) risk across coding and noncoding sequence remains unclear. We analyzed DNVs in 41,367 parent-child sequenced trios from three autism family-based cohorts and compared DNV characteristics and enrichment patterns in males and females. Importantly, these trios consisted of some trios with individuals with autism and some without autism. We developed a new sex-aware DNV caller and performed intensive, feature-based investigation of each candidate DNV to produce a high-confidence callset. We identified enrichment of missense and loss-of-function (LOF) DNVs both overall and within known autism-related genes (i.e., SFARI genes). Gene-specific enrichment analyses revealed twelve genes that were exome-wide significant and specific to males, for significance, including FOXP1, SMAD6, AUTS2, CCDC168, PIEZO1, EML6, ZNF84, IGSF23, OTOG, SLC6A1, GIGYF1, and FREM3 and four genes that were specific to females, for significance, including TAOK1, MECP2, DDX3X, and TBL1XR1 within a variant class. Direct comparisons of DNVs in males and females revealed GABBR2 as the only gene trending toward enrichment in the direct males with autism comparison to females with autism. Finally, we analyzed promoters and identified a single significant promoter region (p = 3.8x10-13), associated with the WDR74 gene, with the signal driven by DNVs observed in males with autism. Surprisingly, the noncoding RNA gene RNU2-2 lies within this significant WDR74 promoter and accounted for most of the DNVs in the region. RNU2-2 DNVs were present in 0.2% of males with autism, and several are predicted to potentially alter RNA folding. We also observed RNU2-2 DNVs in 0.2% of females with autism, including two DNVs that were recurrent (i.e., shared) with unrelated, affected males. Notably, RNU2-2 DNVs were detected in 0.1% of unaffected males and were not observed in unaffected females. Together, these results suggest that although RNU2-2 does not show a sex bias, it contributes to autism risk, which is intriguing due to a prior study implicating RNU2-2 in a severe neurodevelopmental disorder.

BackgroundThe transport of transfer RNAs (tRNAs) from the nucleus to the cytoplasm is a crucial step in the regulation of gene expression and protein synthesis. This process is mediated by specialized export molecules, among which XPOT (Exportin-t, XPO3) plays a central role by recognizing and transporting mature tRNAs through the nuclear pore complex. XPOT is not essential in RNA trafficking in the simple organisms, however the potential impact of XPOT deficiency in human health remains unresolved. MethodsWe identified eight patients from five unrelated families with rare biallelic germline variants in XPOT resulting in putative loss-of-function. Functional analyses were carried out in patient-derived fibroblasts, lymphoblastoid cells and zebrafish models. Ex vivo immunohistochemical stainings for Xpot were performed in the mouse cochlea. xpot knockout zebrafish models were generated to assess the morphology and hearing ability. ResultsAll patients presented with a uniform clinical phenotype that included increased susceptibility to infection, bronchiectasis, severe sensorineural hearing loss, developmental delay, and growth retardation. We demonstrated a complete absence of XPOT protein expression in three patient-derived cell lines. XPOT deficiency leads to disruptions in protein synthesis of the cytokine TNF pathway upon cellular stimulation. Additional XPO1 inhibition in XPOT deficient cells had little effect on cellular functions, suggesting alternative tRNA nuclear transporter pathways. Increased XPOT immunoreactivity was observed in type I spiral ganglion neurons and hair cells of the mouse cochlea, with enrichment in stereocilia. xpot knockout zebrafish model showed dysmorphic features, and reduced hearing, recapitulating key patient phenotypes. ConclusionsOur findings establish a direct connection between impaired XPOT-dependent tRNA export and human pathology. It illustrates that perturbations in nuclear export pathways lead to disease. It also raises the possibility that other nuclear transport receptors may play similarly underappreciated roles in human health and disease. The identification of XPOT as a disease-associated gene opens up new research directions and potential targets for therapeutic intervention.

BackgroundExome sequencing (ES) has become a key diagnostic tool for rare diseases (RDs). However, most evidence on ES performance comes from high-income countries and patients from European ancestry. In countries such as Chile, limited access to next generation sequencing amplifies health disparities and highlights the need to identify which patients are most likely to benefit from ES. MethodsThis study presents the second phase of the Chilean DECIPHERD project, in which we performed ES in a new group of patients with RDs presenting with multiple congenital anomalies (MCA), neurodevelopmental disorders (NDD), and/or suspected inborn errors of immunity. To identify clinical and demographic factors associated with an increased probability of obtaining an informative ES result, we conducted a logistic regression analysis, combining the results of the first and second phases of the project. We also objectively evaluated global ancestry measured using ADMIXTURE, as a potential factor. ResultsSixty-seven patients participated in this second phase of DECIPHERD with a median age of 6 years (range: 0-27); 55.2% were female, with an average ({+/-} s.d.) proportion of Native American ancestry of 0.615 {+/-} 0.18. Clinically, 52.2% presented with both MCA and NDD, and the rest had other phenotype combinations. An informative result, including pathogenic or likely pathogenic variants in genes consistent with the patients phenotype, was identified in 34.3% of the cohort; 61% of these variants had not been previously reported in databases such as ClinVar. By combining the two phases of the study, we reached a total of 167 patients, in whom the presence of NDD and/or MCA significantly increased the probability of achieving an informative ES outcome. In contrast, previous use of gene panel testing was associated with a decreased likelihood of receiving an informative result. Ancestry was not associated with diagnostic yield. ConclusionsThis study demonstrates the utility of ES in achieving a diagnosis in a clinically diverse cohort of Chilean patients with RDs, and characterized features associated with a higher diagnostic yield. These findings may contribute to evidence-based patient prioritization strategies in settings with limited access to NGS resources.

ImportanceGenome-wide association studies have identified hundreds of common single nucleotide polymorphisms (SNPs) and small insertions/deletions (indels) associated with primary open-angle glaucoma (POAG) risk, though these variants have modest effect sizes and individually may have minor contributions to disease development. As whole-genome sequencing data is becoming more readily available, structural variants and other complex genomic features can be interrogated for contribution to disease risk. ObjectiveTest the association of structural variants in known glaucoma loci with disease risk. DesignCross-sectional study. SettingA multicenter cohort of individuals from the United States who contributed genomic and electronic health record data to the All of Us Research Program. ParticipantsPOAG case/control cohorts were generated in the All of Us Researcher Workbench using age (>40 for cases, >65 for controls) and ICD 9/10 diagnosis codes. Main Outcomes and MeasuresLogistic regression analyses adjusted for age, sex, and the top 10 principal components of ancestry were used to test association of structural variants within 500 kilobases of 309 known open-angle glaucoma risk loci. The significance threshold after Bonferroni correction was set at p<1.6x10-4. Results516 POAG cases and 18,716 controls of European ancestry from the All of Us v8 data release were included in the analysis. Mean age was 77.0 years among cases and 74.7 years among controls. Females comprised 45.7% of cases and 56.5% of controls. An 8,732 base pair deletion upstream of PITX2 (chr4:110680827-110689558) was associated with 7.3-fold higher odds of POAG (95% confidence interval: 2.9-18.5, p= 2.4x10-5, variant carrier frequency= 1.6% in cases and 0.25% in controls). Functional annotation identified multiple enhancers overlapping the deletion, suggesting that this structural variant likely impacts gene regulation and expression. Conclusion and RelevanceWhole genome sequencing data captures rare structural variants with large effect sizes that are missed by conventional SNP and indel genotyping approaches, enabling improved POAG risk stratification. These data also expand the phenotypic spectrum of structural variation in the PITX2 locus from childhood glaucoma to adult-onset disease, where age at diagnosis and clinical severity may be influenced by the extent of disrupted regulatory elements.

RNA sequencing (RNA-seq) provides a powerful complement to DNA sequencing for uncovering pathogenic defects affecting gene expression and splicing in individuals with genetically undiagnosed rare disorders. However, as large rare disease consortia adopt RNA-seq, challenges arise due to cohort heterogeneity, variability in tissues and sample sizes, and differences in interpretation practices. Here, we present a harmonized analytical and interpretation framework developed by the pan-European Solve-RD consortium to address these challenges. We analyzed 521 RNA-seq samples from whole blood, fibroblasts, muscle and peripheral blood mononuclear cells collected across more than 30 clinics and five European Reference Networks. Aberrant expression and splicing events were identified using OUTRIDER and FRASER 2.0 and analysed through a standardized four-level scoring framework that encompassed RNA-seq outlier reliability, phenotype relevance, variant mechanism, and segregation evidence, captured in structured reports for interpretation. Regular meetings, and collaborative "Solvathon" workshops were used to evaluate variant pathogenicity. This effort resulted in molecular diagnoses for 19 families out of 248 (7.7%) for whom DNA analyses had been inconclusive. Furthermore, three cases diagnosed using DNA analyses were confirmed, and 49 candidate events and five novel candidate disease genes were identified in the remaining families. Our results demonstrate the feasibility and impact of large-scale, standardized RNA-seq analysis in a transnational research setting. This framework provides a model for other international initiatives such as the Undiagnosed Diseases Network and ERDERA, paving the way for broader clinical implementation of transcriptome-based rare disease diagnostics.

Abstract Background Understanding the phenotypic spectrum of disease-associated genes is essential for accurate diagnosis and targeted therapy. FRMPD4 (FERM and PDZ Domain Containing 4) has previously been associated with intellectual disability and epilepsy. However, its potential role in non-syndromic hearing loss has not been explored. Methods We performed genetic analysis in two unrelated families presenting with non-syndromic sensorineural hearing loss, identifying maternally inherited missense variants in FRMPD4. Clinical phenotyping included audiological assessment and evaluation for neurodevelopmental involvement. Cross-species expression analyses were conducted in Drosophila, zebrafish, and mouse. Functional characterization included quantitative evaluation of sound-evoked responses in Drosophila nicht gut hoerend (ngh) mutants, assessment of neuronal development and acoustic startle responses in zebrafish loss of function models, and morphological cochlear analyses with auditory brainstem response measurements in knockout mice. Results Three affected males from two unrelated families presented with prelingual, bilaterally symmetrical sensorineural hearing loss, with confirmed congenital onset in one individual and no evidence of neurodevelopmental abnormalities. Cross-species analyses demonstrated evolutionarily conserved expression of FRMPD4 in auditory structures. In Drosophila, quantitative analysis of sound-evoked responses in ngh mutants revealed impaired auditory function. Zebrafish loss of function models exhibited reduced neuronal populations in the otic vesicle and posterior lateral line, abnormal neuromast development, and diminished acoustic startle responses. In mice, Frmpd4 knockout resulted in high-frequency hearing loss and cochlear abnormalities consistent with the human phenotype. Conclusions Our findings expand the phenotypic spectrum of FRMPD4 to include non-syndromic sensorineural hearing loss and establish its evolutionarily conserved role in auditory function. These results have direct implications for genetic diagnosis and variant interpretation in patients with hearing loss.

Low-frequency variants (LFVs), defined by minor allele frequencies (MAF) of 1-5%, occupy the gap between common and rare variants in both frequency and effect size. The conventional genome-wide association study (GWAS) significance threshold (5x10-) is overly conservative for LFVs, which account for more than 25% of variants in GWAS. This limitation may obscure meaningful associations in highly heritable yet genetically complex disorders such as autism spectrum disorder (ASD). We hypothesize that the scarcity of significant LFVs in ASD GWAS reflects statistical constraints rather than a true lack of association. To address this, we derived a MAF-specific genome-wide significance threshold using linkage disequilibrium-informed simulations applied to ASD GWAS summary statistics, identifying 2.03x10- as optimal. Applying this threshold revealed three novel LFVs mapping to zinc finger proteins (ZNF420, ZNF781) and known ASD-related genes (KMT2E, PRKDC, MCM4). Enrichment analyses suggested their function in nervous system development and gene regulation. Our findings highlight the contribution of LFVs to ASD risk and underscore the importance of frequency-aware association strategies.

tRNA-derived fragments (tRFs) are relatively recently discovered class of small RNAs implicated in gene-regulatory processes in diverse biological contexts but there have been very few reports of a clear phenotypic role of these small RNAs in cancer progression. By analyzing small RNA-seq data from The Cancer Genome Atlas (TCGA), we found that high expression of three 3' tRFs (tRF-3a), tRF-3009a, tRF-3021a or tRF-3030a, is significantly associated with poor overall survival in low-grade glioma (LGG). In glioblastoma cells, tRF-3009a, tRF-3021a and tRF-3030a enhance cell invasion and migration but tRF-3021a was uniquely required for cell proliferation and suppression of apoptosis. Interestingly, tRF-3021a knockdown decreases global protein synthesis prior to and independent of apoptosis. These data indicate that tRF-3021a supports glioma cell survival and particularly protein synthesis while promoting cellular invasion and migration. Given its association with poor outcome in LGG patients, tRF-3021a represents a promising biomarker and potential therapeutic target in gliomas and these results provide a foundation for future studies to define its molecular interactors and downstream pathways controlling protein synthesis and apoptosis in cancer cells. ImplicationtRF-3021a promotes malignant glioma phenotypes, sustains global protein synthesis and prevents spontaneous apoptosis, motivating efforts to evaluate it as a biomarker and therapeutic target.

Wolfram syndrome is a rare genetic disorder characterized by antibody-negative early-onset atypical diabetes mellitus, optic nerve atrophy, sensorineural hearing loss, diabetes insipidus (arginine vasopressin deficiency), and progressive neurodegeneration, with significant variability in disease severity. We assessed the accuracy of a genotype-based severity scoring system to predict the onset of cardinal symptoms in Wolfram syndrome. This system is based on the type of WFS1 variants (in-frame or out-of-frame) and their location relative to transmembrane domains. Severity scores were assigned to 324 patients with documented onset ages for diabetes mellitus, optic atrophy, hearing loss, and diabetes insipidus. Our analysis revealed a clear correlation between severity scores and earlier onset of diabetes mellitus and optic atrophy. Patients with in-frame variants outside transmembrane domains exhibited milder symptoms, especially WFS1 c.1672C>T (p.Arg558Cys) variant, whereas those with out-of-frame variants showed the earliest onset. Severity scores 3 and 4 did not follow the expected progression, suggesting that transmembrane domain involvement in both alleles may result in greater severity. These findings suggest that this scoring system provides valuable insights into the progression of Wolfram syndrome and may guide clinical care. Further refinement may improve its utility for predicting the onset of non-diabetic symptoms.

MET exon 14 skipping is a pathogenic event that results in decreased ubiquitin-mediated degradation of the MET receptor, sustained oncogenic signaling, and conferred sensitivity to MET tyrosine kinase inhibitors. While exon 14 skipping is most commonly caused by somatically acquired base substitutions and small indels near the exon 14 splice sites, here we report nine cases in which long interspersed element-1 (LINE-1, L1)-mediated insertions within or adjacent to MET exon 14, including one case of a LINE-1-mediated pseudogene insertion, appear to cause exon 14 skipping. These describe the first recurrent and clinically actionable mutations caused by LINE-1 retrotransposition in cancer.

Genotype-phenotype databases are essential for variant interpretation and disease gene discovery. Genetic variation differs among human populations, mainly in allele frequencies and haplotype patterns shaped by ancestry and demographic history. Population-specific genotypes can influence traits and disease risk; this makes population specific characterization important. Most existing resources focus on the characterization of a population's genetic background, but do not represent the resulting phenotypes. We have developed PAVS (Phenotype-Associated Variants in Saudi Arabia), a curated, publicly accessible database that integrates 5,132 Saudi clinical cases from four Saudi cohorts and 522 cases from analysis of a mixed-population cohort, together with 1,856 cases from the Deciphering Developmental Disorders study (DDD) and 9,588 literature phenopackets. Each case record describes patient-level phenotypes, encoded with the Human Phenotype Ontology (HPO), and links them to genomic variants, gene identifiers, zygosity, pathogenicity classifications, and disease diagnoses mapped to standardized disease terminologies. The data is represented in Phenopackets format and as a knowledge graph in RDF. Additionally, a web interface provides phenotype-based similarity search, gene and variant browsers, and an HPO hierarchy explorer. We evaluate the utility of the phenotype annotations for gene prioritization using semantic similarity. While there are clear differences to global literature-curated databases, phenotypes in PAVS can successfully rank the correct gene at high rank (ROCAUC: 0.89). PAVS addresses a gap in population-specific genotype-phenotype resources and provides a benchmark for phenotype-driven variant prioritization in under-represented populations.

BackgroundWhole-genome sequencing (WGS) has improved the diagnosis of rare genetic disorders, yet interpretation of non-coding variants that affect splicing remains challenging. In silico predictions alone are insufficient, and short-read RNA sequencing may fail to capture complex or low-abundance splicing events. Targeted amplicon-based long-read RNA sequencing (Amp-LRS) offers a cost-effective approach for functional validation of candidate splice-altering variants. MethodsWe applied Amp-LRS to five patients with neurological disorders (central nervous system, peripheral nervous system, or muscle) harbouring candidate non-coding variants predicted to alter splicing. RNA was extracted from fibroblasts or peripheral blood, and full-length transcript amplicons were sequenced using Oxford Nanopore Technologies. Nonsense-mediated decay (NMD) inhibition was performed on fibroblast cultures using cycloheximide. ResultsAmp-LRS validated all five candidate variants, including intronic and UTR variants in POLR3A, OPA1, PYROXD1, GDAP1, and SPG11. Aberrant splicing events included exon skipping, intron retention, cryptic splice site activation, and pseudoexon inclusion, often resulting in frameshifts and premature termination codons. For POLR3A and OPA1, multiple abnormal isoforms arose from single variants, highlighting the complexity of splicing disruption. Some pathogenic effects were detectable only in a minority of reads and variably enriched by NMD inhibition, consistent with being hypomorphic. The approach was successfully applied using accessible tissues and enabled multiplexed sequencing at low per-sample cost. ConclusionsAmp-LRS is a sensitive, versatile, and cost-effective method for functional assessment of non-coding splice-altering variants identified by WGS. By enabling full-length transcript analysis from accessible tissues, this approach improves interpretation of variants of uncertain significance and could enhance molecular diagnosis in rare neurological diseases.

Despite the multidimensional value of implementing genomic medicine, in terms of diagnostic yield, cost-effectiveness, and optimisation of care trajectories, its deployment in many African countries, including Algeria, remains constrained by major structural and interpretive challenges, compounded by the persistent underrepresentation of African populations in genomic databases with direct consequences for variant interpretation and clinical decision-making. We implemented a fully in-house whole-exome sequencing (WES) workflow structured through a clinically driven sequential framework in 14 unrelated patients with unexplained neurodevelopmental disorders, in a context of high consanguinity and enriched recessive inheritance. A definitive molecular diagnosis was established in 8 cases, with pathogenic or likely pathogenic variants identified in MECP2, PTPN11, FOXG1, ARV1, GNAO1, ATM, ROBO3, and CHD3. Five cases yielded variants of uncertain significance and one clinically relevant incidental finding was identified. Beyond its diagnostic contribution, this study reveals persistent interpretive limitations: a disproportionate VUS burden, complex incidental finding management, and reduced accessibility to classification criteria, reflecting database underrepresentation, the predominance of private variants, and the limits of current frameworks in consanguineous settings. These findings underscore the necessity of population-specific reference datasets, iterative phenotyping, adapted ethical frameworks, and strategies addressing territorial disparities in access. This work demonstrates that WES implementation requires a structured multidisciplinary ecosystem integrating clinical, bioinformatic, and ethical dimensions, and provides a transferable model for the sustainable integration of genomic medicine in under-resourced settings, while highlighting the global scientific value of incorporating underrepresented populations into genomic research.

Introduction Pathogenic germline variants in the BRCA1 and BRCA2 genes confer a markedly increased risk of breast and ovarian cancer, for which effective preventive strategies are available. Although national and international guidelines recommend BRCA testing and cascade screening of relatives, implementation in Italy remains highly heterogeneous across regions. This study estimates the potential population health and cost impact of achieving full nationwide implementation of BRCA1/2 cascade screening in Italy and identifies key organisational barriers and priority actions for implementation. Methods We conducted a Health Impact Assessment integrating literature review, simulation modelling, and stakeholder consultation. A decision tree and Markov model compared the current heterogeneous implementation of BRCA screening in Italy with an ideal scenario reflecting full adherence to national guidelines, optimal cascade screening, and uptake of preventive strategies. Outcomes included breast and ovarian cancer incidence and mortality, healthcare costs over a lifetime horizon (80 years). Key barriers affecting organisational feasibility, acceptability, and patient well-being were assessed, and a set of priority action recommendations was developed. Results In the ideal scenario, 25,626 eligible cancer patients would undergo BRCA testing annually, identifying 4,254 mutation carriers and enabling cascade testing of 27,650 relatives, of whom 8,682 would be BRCA-positive. Under the current implementation, only 8,807 patients and 2,168 relatives are tested, identifying 948 carriers. Over 30 years, full implementation would prevent 821 cancer cases (- 27.9%) and 1,282 deaths (- 49.7%) compared with the current scenario. While initial expenditures increase due to expanded testing and preventive interventions, cumulative costs decrease over time, resulting in net savings of 5.8 million euros at 30 years and a saving per event avoided (- 2,779 euros). Major implementation barriers include fragmented governance, limited access to genetic counselling, heterogeneous laboratory practices, insufficient professional training, and weak referral pathways. Conclusion Full implementation of BRCA1/2 cascade screening in Italy would yield substantial population health benefits and long-term cost savings. Coordinated national governance, standardised pathways, investment in counselling and workforce capacity, and robust monitoring systems are essential to ensure equitable access and sustainable delivery of personalised cancer prevention. This study demonstrates the value of the HIA methodology for evaluating and guiding genomic prevention policies.

Pancreatic ductal adenocarcinoma (PDAC) is a highly lethal cancer characterized by a high abundance of cancer-associated fibroblasts (CAFs), which influence therapy response, tumor biology and tumor aggressiveness. CAFs are a heterogeneous cell type and previous single-cell RNA sequencing (scRNAseq) of PDAC tumors identified three main CAF subtypes: myofibroblastic, inflammatory and antigen-presenting CAFs (myCAF, iCAF, apCAF, respectively). However, scRNAseq on large patient cohorts is often not feasible due to costs and technical constraints. Therefore, bulk RNAseq deconvolution can be used to identify cell types within the heterogeneous tumor microenvironment. Here, Statescope deconvolution was used to identify different cell types of the tumor microenvironment within an early onset PDAC cohort, comprising 74 patients aged under 60. Three CAF populations were identified (iCAFs, myCAFs and desmoplastic CAFs), and their correlations with tumor microenvironment components, mutational signatures and survival were examined. iCAFs were associated with classical-like tumor cells, whereas myCAFs and desmoplastic CAFs correlated with basal-like tumor cells. Desmoplastic CAFs are associated with inflammatory granulocytes/neutrophils, while negatively associating with monocyte-derived macrophages and immature/transitional B cells. No associations were observed between mutational signatures and the abundance of CAF and epithelial tumor subtypes. Interestingly, a high abundance of CAFs, and specifically increased iCAF abundance, was associated with improved survival. This iCAF-mediated survival effect was predominantly apparent in female patients. All in all, deconvolution of bulk RNA sequencing data, followed by its integration with clinical and biological parameters, reveals the heterogeneity and prognostic implications of CAF subpopulations in the tumor microenvironment of early onset PDAC patients.

Both splicing and kinase signaling are biochemical processes that fundamentally determine and shape cell physiology. Although there has been some indication that there is an interaction between the two - splicing can alter the availability of exons encoding kinase targets and kinases can phosphorylate splicing factors - it has yet to be established the extent to which altering splicing factor expression impacts kinase signaling networks. In this work, we implemented a data-driven analysis using ENCODE RNA-sequencing data and prior work mapping post-translational modifications onto splice events to identify candidate splice factor perturbations that show extensive alterations to phosphorylation-encoding protein products. We then replicated the ENCODE knockdown experiments and performed global phosphoproteomics for two candidates, U2AF1 and SRSF3, complementing the transcription-level data. Both knockdowns showed extensive changes in phosphorylation and kinase activities, both basally and upon receptor tyrosine kinase stimulation. U2AF1 knockdown drove decreased JNK-associated cell death signaling but elevated chromosome regulation through CSNK2A1, PLK, and EIF2AK4 activity. SRSF3 knockdown, on the other hand, led to decreased cell cycle signaling through CDK and HIPK2 but increased cytoskeletal signaling through various PAKs. In addition, we found a striking enrichment of phosphorylated splicing regulators in both knockdowns that were linked to their splicing activity, such as HNRNPC, suggesting potential feedback and crosstalk between splice factors through signaling pathway activation. Importantly, comparison of differential phosphorylation measurements from this study to mRNA expression and splicing measurements from ENCODE revealed significant knockdown-dependent protein regulation, not captured by transcriptomic measurements alone, underscoring the value of phosphoproteomic profiling after splice factor perturbations. Combined, the transcriptomics and phosphoproteomics reveal deep interconnection between the two processes that are relevant to understanding cell signaling in health and disease.

Splice site mutations represent a major class of pathogenic mutations in many diseases, as these changes disrupt normal splicing leading to gene expression changes. Cystic fibrosis (CF) results from mutations to the cystic fibrosis transmembrane conductance regulator (CFTR) gene that encodes an essential ion channel. Approximately 13% of the over 2,100 known CFTR mutations disrupt 3 or 5 splice sites and are predicted to cause splicing defects. Because each splicing mutation is rare, developing individualized therapies to treat each one is financially challenging. Exon specific U1 snRNA (ExSpeU1) targets the non-conserved intronic region downstream the 5 splice site (ss) to rescue exon skipping. Because this approach is exon-rather than mutation-specific, a single agent can potentially rescue multiple mutations. In this study, we have developed a platform to systematically classify all patient variants associated with an exon that are predicted to affect splicing and then determine their rescue potential using ExSpeU1. Here we report the results of these studies. Our minigene reporter study shows that 7 of 10 exon 18 variants resulted in exon skipping. Four mutations at the 3 and 5 ss were rescued at least partially using a single ExSpeU1. Using a luciferase reporter, we observe that the splicing rescue is reflected at the protein level. Lastly, we demonstrate exon-targeting ExSpeU1s can also rescue 3 and 5 ss mutations. Overall, this study exemplifies the power of our platform to screen and rescue multiple patient-derived splicing mutations using a single agent.

Neurexin 1 (NRXN1) is an adhesion protein involved in synapse development and function. Mutations in NRXN1 are strongly linked with neurodevelopmental and psychiatric conditions. Mono-allelic NRXN1 mutations are associated with autistic traits, with increased likelihood of co-occurring intellectual disability. However, mono-allelic mutations have variable penetrance and occur in individuals without neurodevelopmental phenotypes. Conversely, bi-allelic mutations, though rarer, are associated with more stable penetrance and severe neurodevelopmental phenotypes. Human induced pluripotent stem cells (iPSC) have been used to study how mutations in NRXN1 impacts its function, with most studies focusing on monoallelic mutations. In this study, we systematically compared monoallelic and biallelic mutations in NRXN1, characterising their effects on molecular, synaptic, and functional phenotypes. Using CRISPR-Cas9, we introduced indels in NRXN1 exon 19, in an iPSC line containing inducible NGN2. These edits caused either mono-allelic or compound bi-allelic frameshift mutations. iPSCs containing either mutation robustly generated glutamatergic neurons, but these neurons displayed reduced expression of major NRXN1 isoforms. Transcriptomic profiling revealed modest gene expression changes in mono-allelic mutant neurons, whereas bi-allelic mutants exhibited extensive dysregulation of gene networks associated with neuronal maturation and synaptic function. Furthermore, synaptic phenotypes were mild in mono-allelic mutants but pronounced in bi-allelic mutant neurons. Both mono-allelic and bi-allelic mutant neurons displayed alterations in neuronal network activity and reduced peak depolarisation responses to KCl stimulation. Together, these data demonstrate that NRXN1 exhibits gene-dosage sensitivity, with bi-allelic disruption of exon 19 unmasking molecular, synaptic, and functional phenotypes that are only modest in mono-allelic mutant neurons.