SEARCH · Search PubMed

Results for “loss-of-function”

Search indexed PubMed citations on genomics, clinical trials, systematic reviews and public health. Explore titles, authors and supplied subject terms, then open the PubMed record.

SourceResearch connectionFrom yearThrough year

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 19 recordsLinked to original sources

PubMed2026

Identification of biallelic loss-of-function PREP variants in three individuals with syndromic intellectual disability.

BACKGROUND: Neurodevelopmental disorders are one of the most prevalent reasons for genetic testing in childhood. Despite the identification of over 1950 associated genes, many proposed candidate genes lack convincing gene-disease validity. The gene PREP encodes the broadly expressed prolyl endopeptidase whose exact function remains largely unknown. A homozygous PREP variant has been reported once as a candidate gene in two siblings with intellectual disability but no functional studies were conducted. METHODS: Exome and trio genome sequencing were performed in two unrelated families as part of larger cohorts. Segregation analysis, RNA sequencing and immunoblots were performed to further examine the pathogenicity of detected PREP variants. RESULTS: We report three individuals from two unrelated families who presented with intellectual disability, behavioural abnormalities, strabismus, generalised muscular hypotonia, dysmorphic facial features and epilepsy. Exome and genome sequencing identified two different homozygous rare PREP variants: c.1570_1573dup, p.(Asn525Thrfs*5) and c.1839-2A>G, p.?. RNA sequencing confirmed the detected intronic variant to result in two aberrant mRNA isoforms. In patient-derived cells immunoblots showed absence of PREP protein. CONCLUSION: Our data suggest PREP deficiency as the underlying cause of a syndromic neurodevelopmental disorder.

Female↗

PubMed2026

Selectivity Filter KCND3 Variant Causes Spinocerebellar Ataxia 19/22 and KV4.3 Functional Loss.

BACKGROUND: Spinocerebellar ataxia type 19/22 (SCA19/22) is a rare autosomal dominant neurodegenerative disorder caused by KCND3 variants encoding the KV4.3 potassium channel. While most pathogenic variants result in loss-of-function (LOF), no pathogenic variants were previously identified in the channel's selectivity filter, a critical domain for ion selectivity. OBJECTIVES: To elucidate the genetic cause and functional LOF mechanisms underlying severe early-onset cerebellar ataxia and neurodevelopmental impairment in monozygotic twins. METHODS: We evaluated twins presenting with early-onset cerebellar ataxia, developmental delay, and cognitive impairment. Whole-exome sequencing (WES) identified a KCND3 c.1103T>C (p.L368P) variant. Functional impacts were assessed through HEK293T cell protein expression, Xenopus oocyte electrophysiology, and structural homology modeling. RESULTS: WES identified a heterozygous de novo p.L368P variant in the "TLGYG" selectivity filter sequence. Modeling predicted a pore radius reduction, blocking potassium permeation. Biochemical analyses revealed markedly reduced protein expression and impaired trafficking. Electrophysiological recordings confirmed complete potassium current loss and a strong dominant-negative effect on wild-type KV4.3 currents. Clinically, the twins exhibited severe intellectual disability, developmental delay, and cerebellar atrophy with pontine flattening, without epilepsy. CONCLUSIONS: Identifying the first pathogenic variant in the KV4.3 selectivity filter highlights its critical role in channel proteostasis and ion conductance. The p.L368P variant produces a pronounced LOF phenotype and broadens the SCA19/22 clinical spectrum, indicating the filter's structural integrity is a key determinant of disease severity. © 2026 International Parkinson and Movement Disorder Society.

KCND3↗

PubMed2026

Context-dependent effects of MIR100HG on tumorigenic phenotypes and p38/MAPK-AKT signaling in hepatocellular carcinoma.

Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related mortality worldwide and is characterized by a hypoxic tumor microenvironment that promotes tumor progression, cellular adaptation, and therapeutic resistance. Increasing evidence indicates that long non-coding RNAs (lncRNAs) play critical roles in regulating tumor-associated signaling networks; however, the contribution of MIR100HG to hepatocellular carcinoma progression, particularly under hypoxic conditions, remains insufficiently understood. In this study, we investigated the expression pattern and functional significance of MIR100HG in hepatocellular carcinoma using epithelial-like Hep3B and mesenchymal-like SNU-398 cells, together with non-tumor hepatocytes (Clone-9). Gain- and loss-of-function approaches were employed to evaluate the impact of MIR100HG on tumor-associated cellular phenotypes under both normoxic and hypoxic conditions. Functional assays demonstrated that MIR100HG overexpression significantly enhanced cell proliferation, clonogenic potential, migration, and invasion, whereas MIR100HG silencing markedly suppressed these tumorigenic properties and increased apoptotic cell death. Mechanistic analyses revealed that MIR100HG promotes oncogenic signaling through the p38/MAPK and AKT pathways under normoxic conditions, whereas MIR100HG depletion reduced the phosphorylation of these key signaling proteins. Notably, additional pathway analyses under hypoxia-mimicking conditions revealed a distinct signaling response, in which the MIR100HG-associated activation of p38/MAPK and AKT observed under normoxia was not maintained. Moreover, the expression patterns of AKT-associated regulatory genes, including GAS6 and PTEN, were reversed under hypoxia-mimicking conditions. These findings suggest that the effects of MIR100HG on oncogenic signaling are highly dependent on the cellular oxygenation context and that hypoxia reshapes the downstream signaling consequences of MIR100HG expression in HCC cells. Collectively, our findings identify MIR100HG as a hypoxia-associated oncogenic regulator that enhances tumorigenic phenotypes and promotes survival signaling in hepatocellular carcinoma. These results highlight MIR100HG as a potential biomarker and therapeutic target in liver cancer and provide new insights into the molecular mechanisms underlying hypoxia-driven tumor progression.

Humans↗

PubMed2026

OLR1 drives gastric cancer progression through NF-κB activation and immunosuppressive macrophage polarization.

Gastric cancer remains a leading cause of cancer-related mortality worldwide, and the identification of clinically relevant biomarkers is critical for improving patient outcomes. Oxidized low-density lipoprotein receptor 1 (OLR1) has been implicated in tumor progression; however, its role in gastric cancer and the tumor microenvironment remains unclear. OLR1 expression and clinical significance were analyzed using The Cancer Genome Atlas (TCGA) dataset and validated in gastric cancer cell lines. Gain- and loss-of-function experiments, together with in vitro and in vivo assays, were performed to investigate the biological functions and underlying mechanisms of OLR1 in gastric cancer progression. OLR1 was significantly upregulated in gastric cancer and associated with unfavorable prognosis. Functional analyses demonstrated that OLR1 promoted gastric cancer cell proliferation, migration, and tumor growth. Mechanistically, OLR1 activated NF-κB signaling and facilitated macrophage polarization toward the M2 phenotype, thereby contributing to a protumorigenic microenvironment. OLR1 promotes gastric cancer progression through activation of NF-κB signaling and modulation of macrophage polarization. These findings identify OLR1 as a potential prognostic biomarker and therapeutic target for gastric cancer.

Humans↗

PubMed2026

TWIST2-dependent transcriptional activation of TPI1 mediates TGF-β1-driven fibroblast activation in pulmonary fibrosis.

Idiopathic pulmonary fibrosis (IPF) is a progressive and fatal interstitial lung disease characterized by aberrant profibrotic signaling and excessive extracellular matrix deposition, accompanied by fibroblast-to-myofibroblast transition. Despite extensive investigation, the molecular mechanisms underlying IPF pathogenesis remain incompletely understood. Here, we investigated the role of triosephosphate isomerase 1 (TPI1) in IPF progression and its regulation by transforming growth factor-β (TGF-β) signaling. Loss-of-function analyses identified TPI1 as a downstream effector of TGF-β1, as its knockdown markedly suppressed fibrotic marker expression, fibroblast proliferation, and migration. Mechanistically, TWIST2 was shown to function as a direct transcriptional regulator of TPI1, binding to its promoter and promoting transcriptional activation. Rescue experiments further confirmed that the TWIST2-TPI1 axis is central to the progression of pulmonary fibrosis. Notably, knockdown of either TPI1 or TWIST2 effectively attenuated TGF-β1-induced fibrotic phenotypes. Collectively, these findings define the TGF-β1/TWIST2/TPI1 signaling axis as an important regulator of pathogenic fibroblast behavior and pro-fibrotic responses through transcriptional control of TPI1, highlighting its potential as a therapeutic target for IPF.

Twist-Related Protein 1↗

PubMed2026

PRDX1 facilitates USP7-dependent stabilization of SCD1 and promotes bladder cancer progression.

Bladder cancer is characterized by redox adaptation and metabolic plasticity, but the mechanisms linking these processes remain incompletely understood. Integrating bulk, single-cell, and spatial transcriptomic analyses, we identified PRDX1 as a malignant epithelial cell-associated factor linked to adverse outcome. Genetic gain- and loss-of-function studies showed that PRDX1 promoted proliferation, motility, and xenograft growth while limiting reactive oxygen species accumulation and mitochondrial apoptosis. Proteomic and biochemical analyses identified an association between PRDX1 and SCD1. PRDX1 prolonged the SCD1 protein half-life without detectably altering SCD1 transcript abundance and increased USP7-SCD1 co-precipitation. USP7 removed K48-linked polyubiquitin chains from SCD1 and prevented its proteasomal degradation, whereas catalytically inactive USP7 failed to deubiquitinate SCD1. Deletion of PRDX1 residues 157-199 weakened its association with SCD1 and reduced USP7-SCD1 co-precipitation. Depletion of SCD1 or USP7 suppressed PRDX1-dependent growth in vitro and in xenografts. These findings support a model in which PRDX1 facilitates USP7-dependent stabilization of SCD1 and promotes bladder cancer progression.

Bladder cancer↗

PubMed2026

Whole-exome characterization of host genetic variation in HIV-associated genes across the high-prevalence Mizo population, Northeast India.

BACKGROUND: The Mizoram state of Northeast India has one of the highest HIV prevalence rates in Asia, yet the host genetic factors influencing HIV susceptibility in this Tibeto-Burman population remain uncharacterised. METHODS: We performed whole-exome sequencing using Illumina NovaSeq 6000, mean coverage 100X on 76 HIV-negative Mizo individuals. Variants were called using GATK HaplotypeCaller v4.3 against GRCh38p14, annotated with ANNOVAR, and filtered using hard-quality thresholds (QD ≥ 2, SOR ≤ 3, MQ ≥ 40, DP ≥ 10, GQ ≥ 20). The allele frequencies were compared against gnomAD v2.1.1 population databases. Hardy-Weinberg equilibrium was assessed using the Wigginton exact test with Bonferroni correction. RESULTS: Post-quality filtering resulted in 12,011 sample-variants across 2,821 unique positions from 36 HIV-associated loci (33 protein-coding genes, 2 chemokine ligands, and 3 lncRNA targets). Of these, 784 observations (51 unique positions) were high-impact nonsynonymous or loss-of-function variants. ADAR rs2229857 (p.K384R, NM_015840) was the most frequently observed variant (Mizo carrier frequency = 0.895; 95% CI: 0.806-0.946). CXCR1 rs16858808 (p.R335C) showed the greatest population enrichment (Mizo carrier frequency = 0.197; 95% CI: 0.123-0.300; 7.65-fold carrier-frequency enrichment versus gnomAD South Asian; CADD = 15.60). Sixteen of 20 tested variants deviated from Hardy-Weinberg equilibrium after Bonferroni correction (p < 0.0025), predominantly showing excess homozygosity consistent with the endogamous Mizo population. The protective variant CCR5-Δ32 was absent in all the 76 individuals tested. CONCLUSION: This first whole-exome characterization of HIV host genes in the Mizo population identifies CXCR1 rs16858808 as the most population-enriched functional variant and reveals a pervasive endogamy signature. These findings provide a population-specific genetic framework for future HIV susceptibility studies and ART pharmacogenomics research.

Humans↗

PubMed2026

Monogenic ALB Variants as Determinants of Severe Hypercholesterolemia: A Population-Based Cohort Study.

BACKGROUND: Hypoalbuminemia is associated with several risk factors for myocardial infarction, including hypercholesterolemia, liver disease, kidney disease, and diabetes. Homozygosity of loss-of-function (LoF) variants in the ALB gene, which encodes albumin, is a known cause of congenital hypoalbuminemia. Studies have also shown that heterozygous ALB LoF variants are associated with increases in low-density lipoprotein cholesterol (LDL-C), comparable to those seen in familial hypercholesterolemia. OBJECTIVES: This study examined the effect of ALB LoF variants and other causes of low albumin on LDL-C levels in 2 population biobanks. METHODS: This study used data from 2 large cohorts with linked electronic health record and genetic information: Geisinger's MyCode Community Health Initiative, a health care population based in Pennsylvania, USA; and the National Institutes of Health All of Us Research Program, a nationwide epidemiologic cohort. LDL-C values were adjusted for lipid-lowering medication use. Myocardial infarction diagnoses were extracted from electronic health records using International Classification of Diseases codes. A polygenic score for serum albumin was calculated for participants of European ancestry. Linear regression models were used to estimate associations, and results were meta-analyzed across cohorts using fixed-effects models. RESULTS: Among 155,530 MyCode and 405,701 All of Us adult participants, 77 individuals (1 of 7,289) carried an ALB LoF variant. Among noncarriers, a 1 g/dL decrease in serum albumin was associated with a 10.9 mg/dL (95% CI:, 10.4-11.4) decrease in LDL-C. In contrast, ALB LoF variants were associated with a 0.69 g/dL (95% CI: 0.60-0.78) reduction in serum albumin and a 38.3 mg/dL (95% CI: 28.2-48.5) increase in LDL-C. Paradoxically, whereas monogenic determinants of hypoalbuminemia were associated with increased LDL-C, polygenic determinants of lower albumin were associated with a 0.22 mg/dL (95% CI: 0.17-0.26) decrease in LDL-C per decile. CONCLUSIONS: ALB LoF variants represent a previously underrecognized monogenic cause of elevated LDL-C, with effect sizes slightly less than canonical familial hypercholesterolemia variants. The divergent effects of ALB-mediated vs polygenic or physiological reductions in albumin on LDL-C suggest distinct underlying mechanisms.

Humans↗

PubMed2026

Intellectual disability, neuroregression and adult-onset progressive dystonia due to a DLG4 pathogenic variant.

We report a 34-year-old male with childhood developmental delay, severe intellectual disability in adulthood, episodes of agitation with a previous diagnosis of schizoaffective disorder and adult-onset cognitive regression who developed progressive generalised dystonia due to a de novo DLG4 pathogenic loss-of-function variant. This case expands the phenotypic spectrum of recognised movement disorder manifestations associated with DLG4-related synaptopathy.

Humans↗

PubMed2026

Generation of two induced pluripotent stem cell lines from hereditary hemorrhagic telangiectasia patients harboring ACVRL1 mutations.

Hereditary hemorrhagic telangiectasia (HHT) is an autosomal dominant vascular disorder in which dysregulated endothelial signaling drives telangiectasias and arteriovenous malformations across multiple organs. Loss-of-function variants in ACVRL1 (ALK1), a core receptor in BMP9/10 signaling, are a major genetic cause. Here we report two patient-derived induced pluripotent stem cell (iPSC) lines generated from clinically diagnosed HHT donors carrying heterozygous ACVRL1 mutations: c.129dup (p.Pro44Alafs*125) and c.430C > T (p.Arg144*). Both lines showed expected iPSC morphology, robust expression of markers of the undifferentiated iPSC state, genomic stability by LP-WGS, and tri-lineage differentiation capacity. These resources enable human cell-based studies of ACVRL1 haploinsufficiency and provide a starting point for mechanistic and therapeutic work focused on HHT vascular pathobiology.

Journal Article↗

PubMed2026

Establishment of a human induced pluripotent stem cell line, KMUGMCi011-A, from a patient bearing a frameshift mutation in the KMT2D gene leading Kabuki syndrome 1.

Kabuki syndrome 1 is a rare genetic disorder typically characterized by facial abnormalities, cognitive impairment, developmental delay and organ dysfunction. It is caused by a loss-of-function mutation in the KMT2D gene. The peripheral blood mononuclear cells from a patient carrying frameshift mutation in the KMT2D gene were reprogrammed using the CytoTune-iPS2.0 Sendai Reprogramming Kit. This frameshift mutation results in a truncated protein. This established human induced pluripotent cell line will allow proper in vitro disease modelling of Kabuki syndrome 1.

Journal Article↗

PubMed2026

Unveiling the power of TIIC: A prognostic tool for esophageal adenocarcinoma.

BACKGROUND: Esophageal adenocarcinoma (EAC) remains a lethal malignancy with limited prognostic tools for guiding immunotherapy. Tumor-infiltrating immune cells (TIICs) play a critical role in EAC prognosis and treatment response. METHODS: We integrated single-cell RNA sequencing and bulk transcriptome data from TCGA and GEO databases. TIIC-specific RNAs were identified via tissue specificity index calculation combined with machine learning feature selection. Twenty machine learning algorithms were benchmarked to construct an optimal TIIC signature score (TIIC-Score) based on the comprehensive C-index. Immunotherapy response, genomic mutation, and copy number variation were analyzed. Summary-data-based Mendelian randomization (SMR) and two-sample Mendelian randomization (MR) were performed to explore genetic associations. Core prognostic TIIC-related genes were functionally validated in esophageal cancer cell lines through loss-of-function assays. RESULTS: The TIIC-Score demonstrated robust prognostic value for 1-, 2-, and 3-year overall survival across multiple cohorts, outperforming 22 published models. High TIIC-Score was associated with poor survival and increased chromosomal instability. Mutation profiling revealed high frequencies of TP53 (78.2%), TTN (48.7%), and SYNE1 (30.8%). MR analysis identified a significant association between gastro-oesophageal reflux and EAC risk at SNP rs8130507. Functionally, CCNI was upregulated in esophageal cancer cells, and its knockdown suppressed malignant phenotypes while promoting apoptosis, supporting its pro-tumorigenic role. CONCLUSION: The TIIC-Score provides a novel prognostic framework for EAC that effectively stratifies patient risk and may help identify individuals most likely to benefit from immunotherapy.

Esophageal adenocarcinoma↗

PubMed2026

The Jumonji C domain-containing proteins GmJMJ19 and GmJMJ20 link florigen signaling with epigenetic regulation of photoperiodic flowering and post-flowering plant height in soybean.

Soybean (Glycine max) is a photoperiod-sensitive legume whose latitudinal adaptation depends on the precise control of flowering time and plant height. Histone demethylases of the JmjC domain-containing (JMJ) protein family have been implicated in these processes across plant species, but their specific roles in soybean remain largely unexplored. Here, we identify soybean GmJMJ19 and GmJMJ20, two closely related JMJD5/KDM8 orthologs, as master epigenetic regulators that coordinately control both photoperiodic flowering and post-flowering plant height. Both genes exhibit intrinsic, rhythmic expression peaking at ZT12, and their encoded proteins physically interact with the florigen proteins FT2a and FT5a. Loss-of-function mutants display delayed flowering under long days (LDs) and increased plant height under both LDs and short days (SDs), whereas overexpression phenocopies the mutant flowering phenotype, indicating revealing a critical dosage requirement for proper function. Mechanistically, GmJMJ19 and GmJMJ20 are recruited by the FT/FD transcriptional complex to directly activate AP1a and AP1c expression through chromatin modulation. Population genomic analyses reveal distinct selection signatures: GmJMJ19 underwent sustained directional selection during cultivation, whereas GmJMJ20 experienced an early domestication sweep with limited subsequent change. Haplotype analysis identifies coordinated latitudinal clines, with the JMJ19H1/JMJ20H1 combination predominating at high latitudes to promote early flowering and limit height, while JMJ19H2/JMJ20H2 and wild JMJ19H3/JMJ20H3 alleles prevail at low latitudes, conferring later flowering and increased height. Collectively, our findings establish GmJMJ19 and GmJMJ20 as central chromatin regulators linking florigen signaling to downstream target expression and provide valuable allelic resources for breeding regionally adapted soybean varieties across a wide range of latitudinal environments.

Histone modulation↗

PubMed2026

Mapping genetic modifiers of epimutation rates identifies VIM2/4 as dosage-sensitive negative regulators of CG methylation maintenance.

Spontaneous epimutations are stochastic gains and losses of cytosine methylation that arise from imperfect maintenance across cell divisions. At CG sites, such epimutations can be inherited across generations in plants and constitute a major source of CG methylation (mCG) diversity. However, why the fidelity of mCG inheritance varies among genotypes, and how this variation relates to steady-state mCG levels, remains poorly understood. Here we tracked DNA methylation over 10 generations in ~400 mutation-accumulation lines derived from ~70 Arabidopsis thaliana Ler × Cvi recombinant inbred founders. By treating methylation gain and loss rates as quantitative molecular traits, we mapped a major-effect locus to a Cvi-derived deletion between VARIANT IN METHYLATION (VIM)2 and VIM4, two key components of the METHYLTRANSFERASE 1-dependent mCG maintenance pathway. Lines carrying this deletion showed elevated VIM2/4 (VIM2 and VIM4) expression, a rapid shift of genome-wide mCG towards a lower steady state and reduced fidelity of methylation inheritance across generations. Complementary overexpression and loss-of-function experiments identify VIM2/4 as dosage-sensitive negative regulators of mCG maintenance, in contrast to the canonical positive role of VIM-family proteins in mCG. Together, our results support a punctuated-equilibrium model of DNA methylome evolution, in which naturally segregating modifiers of mCG homeostasis can produce abrupt shifts in methylation state and alter the rate at which heritable epigenetic variation accumulates in plant genomes.

Journal Article↗

PubMed2026

Chemogenomic maps reveal a PRDX1-dependent iron-damage axis in the DNA damage response.

The DNA damage response (DDR) is a sophisticated network of cellular pathways whose perturbation leads to genome instability and is a key hallmark of oncogenesis. Here, we present data from 32 genome-scale loss-of-function CRISPR interference chemical-genetic screens with inhibitors targeting core constituents of the DDR machinery (PARP, ATR, ATM, DNAPK and WEE1), as both single agents and in combination with poly(ADP-ribose) polymerase inhibitors. These experiments identify >1,000 genes whose perturbation modifies the DDR and provides a rich resource to the DDR community. In addition, this compendium of functional genomics data reveals key principles governing the DDR and highlights a strong chemical-genetic interaction between loss of activity of the peroxiredoxin PRDX1 and all tested DDR inhibitors through a mechanism involving iron availability mediated by an MRGBP-PAX7-IREB2 axis. Our data position PRDX1 as a key suppressor of DNA damage accumulation and potential druggable target in combination with DDR inhibitors.

Journal Article↗

PubMed2026

Maize terpene synthase 8 (ZmTPS8) produces a blend of sesquiterpenes and contributes to defense against pests and pathogens.

Maize (Zea mays) produces terpenoid-based chemical defenses through a large family of terpene synthases, but the contributions of individual enzymes to specific compounds and stress resistance remain difficult to predict. Maize terpene synthase 8 (ZmTPS8) produces multiple sesquiterpenes in heterologous systems, but its in planta function remains unknown. We integrated a metabolite genome-wide association study (mGWAS), CRISPR/Cas9 generated tps8 loss-of-function mutants, metabolite profiling, and biotic stress assays to define ZmTPS8's role in terpene synthesis and biotic stress responses. The mGWAS identified ZmTPS8 as the primary locus associated with herbivore-induced emission of the sesquiterpene volatile germacrene D. Consistently, ZmTPS8 expression was induced by foliar and root herbivory, and tps8 mutants exhibited reduced emission of germacrene D, α-copaene, and δ-cadinene during Spodoptera frugiperda feeding. Loss of ZmTPS8 increased S. frugiperda larval growth but did not affect the belowground herbivore Diabrotica virgifera virgifera. ZmTPS8 also contributed to resistance against sugarcane mosaic virus, and the fungal pathogen Fusarium verticillioides, affecting terpenoid profiles, global metabolism, and fungal toxin production, but had no impact on Cochliobolus heterostrophus or Pythium spp. susceptibility. Together, these results demonstrate that ZmTPS8 contributes to maize defense in a threat-dependent manner, shaping volatile emissions and defense outcomes.

Zea mays↗

PubMed2026

Involvement of tRNA thiolation in uORF-mediated translational regulation during Xylogenesis in Arabidopsis thaliana.

Post-transcriptional modification of tRNAs is an important mechanism for regulating translation efficiency and cellular homeostasis, yet its contribution to upstream open reading frame (uORF)-mediated translational control remains largely unexplored. In this study, we investigated the role of tRNA thiolation in thermospermine-dependent regulation of xylem development in Arabidopsis thaliana. Using a suppressor screen of the thermospermine-deficient mutant acaulis5 (acl5), which exhibits dwarfism and excessive xylem differentiation, we identified suppressor-of-acl502 (sac502) as a recessive loss-of-function allele of CTU2, a gene encoding a key enzyme in the biosynthesis of the wobble uridine modification 5-methoxycarbonylmethyl-2-thiouridine. Mutations in other components of the same modification pathway, including ROL5 and TRM9, similarly suppressed the acl5 phenotype. Translational analyses using 5' leader-GUS reporter constructs revealed that the ctu2 mutation did not enhance translation of the mRNA containing a thermospermine-responsive uORF of SAC51, but instead significantly reduced translation of that of SACL3, a member of the SAC51 family, and that of LONESOME HIGHWAY (LHW), which contains another conserved uORF in the 5' leader region. Polysome profiling further demonstrated decreased association of SACL3 and LHW mRNAs with actively translating ribosomes in ctu2. Genetic interaction analyses supported the conclusion that the suppression of excessive xylem formation in acl5 by ctu2 is attributable to reduced LHW activity. In addition, ctu2 mutants displayed increased sensitivity to exogenous thermospermine, resembling the response of lhw mutants. Together, our results reveal that tRNA thiolation contributes to uORF-mediated translational regulation of key developmental regulators and identify tRNA modification as an important regulatory layer controlling vascular development.

Arabidopsis↗

PubMed2026

Glycemic and bodyweight effects of GIPR coding variation reflect differences in surface expression and intrinsic functional impairment.

The glucose-dependent insulinotropic polypeptide receptor (GIPR) is a major therapeutic target in type 2 diabetes and obesity. Missense variation in GIPR could confer phenotypic effects through alterations to constitutive activity or functional responses to GIP or pharmacological agonists. In this study, we aimed to provide a deep understanding of the molecular mechanisms that underpin the cellular and physiological impacts of GIPR coding variation by studying 30 GIPR coding variants in cellular models and pancreatic islets. Many variants showed impaired GIP-induced cyclic adenosine monophosphate responses, and population-based association analysis highlighted that these loss-of-function variants decrease body mass index but increase glycemia. In many cases, reduced function was partly driven by reduced expression at the cell surface due to impaired stability and redirection toward proteasomal degradation. Molecular dynamics simulations suggest distinct variant-induced perturbations in inter- and intrahelical interactions, which interfere with receptor stability. This study highlights the mechanisms and consequences of GIPR coding variation, which may have implications for the therapeutic targeting of this receptor.

Humans↗