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Hafner, M.

Publications and source records attributed to Hafner, M..

At least 19 recordsLinked to original sources

Oncofetal RNA-binding proteins of IGF2BP family suppress IRF-3 and NF-kB dependent transcription downstream of cytosolic RNA sensors

Activation of innate inflammatory signaling and tumor-specific antigen presentation in cancer cells provides a foundation for anti-cancer immunotherapies. Here, we show that the insulin-like growth factor 2 mRNA-binding proteins (IGF2BP1, IGF2BP2, and IGF2BP3), which are upregulated across diverse human malignancies, including acute myeloid leukemia (AML), suppress RNA-sensing pattern recognition receptor signaling and downstream ISRE-and NF-{kappa}B-dependent transcription. Among these pathways, RIG-I signaling is particularly sensitive to IGF2BP-mediated inhibition. This suppressive effect is strongest when all three IGF2BP paralogs are co-expressed, especially in embryonic-like hematoendothelial cells and leukemia stem cells. Mechanistically, IGF2BPs suppress innate immune signaling by directly binding to TNFAIP3 mRNA and promoting its expression. Consequently, inhibition of IGF2BPs activates innate immune signaling and induces MHC class I gene expression in AML cells, highlighting IGF2BPs as promising therapeutic targets to enhance RIG-I- and TLR-based cancer immunotherapies. HighlightsO_LIIGF2BP family of proteins regulate PRR responses C_LIO_LIIGF2BP levels affect chromatin accessibility and pan-transcriptome C_LIO_LISV40 large T antigen induces de novo expression of IGF2BPs C_LIO_LITNFAIP3 mRNA levels and stability are regulated by IGF2BPs C_LI

cancer biology↗

Stage-resolved iPSC-to-motoneuron differentiation: Metabolic switch & mitochondrial remodeling

Development of motoneurons from stem cells is characterized by a change from glycolytic to oxidative metabolism. Since this transition remains poorly understood, we examined it at five distinct differentiation stages from hiPSC to motoneuron. While a direct comparison of hiPSCs and mature motoneurons confirmed the expected glycolytic-to-oxidative shift, the intermediate stages showed that the conversion was not monotonic. After an initial drop of glycolysis at the hiPSC-to-neuroepithelial transition, late neuroepithelial cells showed intermittent peaks of the glycolytic marker lactate dehydrogenase A and the metabolic regulator TIGAR. Furthermore, the lactate-produced-to-glucose-consumed ratio remained elevated. A fully oxidative phenotype was only assumed upon progress from neural progenitors to motoneurons, portrayed by a definitive drop of the lactate-produced-to-glucose-consumed ratio, an increase of mitochondrial membrane charging, and shifts from lactate dehydrogenase A to B, from pyruvate dehydrogenase to anaplerotic pyruvate carboxylase, and from Mitofusin 1 to 2. Together, our data show that metabolic maturation in human motoneurons does not occur as a simple switch. Instead, it unfolds through distinct stages in a directional yet nonlinear manner.

developmental biology↗

The human DEAD-box protein DDX3X regulates host and viral mRNA translation during Sendai Virus infection

DDX3X is a multifunctional DEAD-box RNA helicase with important roles in translation initiation and antiviral innate immune signaling, yet it is currently unknown whether viral infection affects its interactions with host RNAs. Here, we define the transcriptome-wide binding landscape of endogenous DDX3X in Sendai virus-infected human cells using PAR-CLIP. We show that DDX3X maintains its preference for GC-rich, highly structured 5'UTR regions during infection, but acquires a distinct set of infection-induced targets, including IFNB1 and multiple interferon-stimulated genes. We demonstrate that DDX3X directly binds the IFNB1 5'UTR and promotes its translation, establishing a previously unrecognized post-transcriptional mechanism contributing to DDX3X-dependent IFN-{beta} production. We also evaluated DDX3Xs binding to SeV RNAs and concluded that DDX3X is likely not actively recruited by SeV or has a significant effect on its viral life cycle. Our findings add a novel dimension to DDX3Xs involvement in anti-viral immunity with implications for further therapeutic development of DDX3X inhibitors.

molecular biology↗

Single-cell profiling reveals pervasive heterogeneity in subcellular RNA localization

Subcellular RNA localization is a fundamental layer of gene regulation, yet its heterogeneity across individual cells remains poorly understood. Here, we introduce the RNA Localization Profiler (RLP), a proximity-based RNA-editing strategy that maps compartment-specific RNAs in living cells. Across the cytoplasm, endoplasmic reticulum (ER), and plasma membrane, RLP identifies robust and highly specific RNA localization programs linked to translation and membrane organization. Single-cell RLP (scRLP) reveals that individual cells harbor roughly 5,000-7,000 cytoplasmic RNAs, with <10% associated with the ER. These measurements uncover pervasive subcellular heterogeneity in RNA localization that is undetectable by bulk assays. Spatial RNA patterns define an orthogonal axis of cell-state identity that is independent of gene expression. For example, ZWINT mRNA relocalizes to the cytoplasm in a cell cycle-dependent manner. These findings establish heterogeneous levels of subcellular RNA localization as a variable dimension of intracellular organization and cell identity.

cell biology↗

Advanced 3D spheroid-based skin models and deep-learning based image analysis enable in-depth investigation of keratinocyte differentiation and barrier function

To date, a panel of different biological models have been used in skin research, ranging from in vivo testing to 2D and 3D cultures. Among these, organotypic skin models represent the current gold standard for preclinical dermatology and toxicology studies. However, they are variable in quality and require long maturation times and a lot of work and cells, the latter often of primary origin. Here, we propose dermal-epidermal spheroids as an alternative model that balances physiological relevance and throughput. Next to corresponding full thickness skin models, different fibroblast/keratinocyte coculture spheroids were generated. These used the commonly employed HaCaT cells as well as two recently immortalized keratinocyte cell lines, NHK-SV/TERT and NHK-E6/E7. To investigate their differentiation with detailed spatio-temporal resolution, a deep-learning segmentation-based pipeline, capable of revealing nuclear morphology and positioning as well as marker expression with single-cell precision, was developed and applied. Moreover, the formation of a functional barrier was assessed by live-imaging of Lucifer yellow diffusion. These experiments identified the NHK-E6/E7 cell line as the most and HaCaT cells as the least suitable alternative to primary keratinocytes in both spheroids and full thickness models. Furthermore, NHK-based coculture spheroids displayed functional maturation, including stratification, cornification, and barrier formation, closely recapitulating these features of corresponding full thickness models. Given the scalability and compatibility with automation, these micro-skin fibroblast/NHK-based 3D coculture spheroids might represent a promising new platform for pharmaceutical, cosmetic, and toxicological testing.

bioengineering↗

RBProximity-CLIP Enables Subcellular Mapping of RNA-Binding Protein Interactions at Nucleotide Resolution

RNA-binding proteins (RBPs) enable post-transcriptional gene regulation (PTGR) through specific interactions with RNA molecules, influencing processes ranging from nuclear processing and export to cytoplasmic localization, translation, storage and degradation. A key determinant of PTGR processes is the subcellular compartmentalization of RBPs, which dictates RNA targets they can access and the regulation performed in that environment. To characterize RBP-RNA interactions at subcellular resolution, we developed RBProximity-CLIP. RBProximity-CLIP enables compartment-specific isolation and profiling of individual RBP-RNA interactions by combining APEX2-based proximity labeling and 4-thiouridine-enhanced RNA-protein crosslinking, with sequential RBP- and biotin-affinity purifications. Using this approach, we profiled the RNA targets of three RBPs, AGO2, YBX1, and ELAVL1, across the cytoplasmic, nuclear, and nucleolar compartments, revealing nucleus-specific miRNA-mediated AGO2 targets, as well as subsets of YBX1 and ELAVL1 targets that differ by compartment, yet share identical binding motifs. RBProximity-CLIP enables specific and sensitive detection of compartment-specific RBP-RNA interactomes, thereby providing new insight into spatial gene regulation by RBPs.

cell biology↗

PCLIPtools: A Robust Framework for Identifying RNA-Protein Interaction Sites from PAR-CLIP experiments.

PAR-CLIP is a widely used method for identifying binding sites of RNA-binding proteins (RBPs) transcriptome-wide. A characteristic T-to-C transition in the sequenced cDNA pinpoints the site of RBP-RNA crosslinking and is induced by the use of a photoreactive uridine analogue, 4-thiouridine (4SU). As with other systems-wide methods, PAR-CLIP, too, is prone to false discoveries as the T-to-C signal might result from systematic noise, pre- existing SNPs, and PCR errors. Therefore, rigorous statistical methods are required for analyzing PAR-CLIP data. The few existing tools to analyze PAR-CLIP data lack updates and sufficient documentation, and often fail to process current higher-depth sequencing data. Here we report PCLIPtools, a lightweight, customizable suite for analyzing PAR-CLIP data. PCLIPtools considers the read depth, T-to-C transitions, and the other mutations to statistically estimate high-confidence interaction sites. Benchmarking shows that PCLIPtools identifies more functionally significant targets than the current standard tool, PARalyzer, without losing high-confidence sites and outperforming it in runtime. Exploratory analyses show PCLIPtools specific targets are enriched for read depth and T-to-C conversion, supporting their validity. With simplicity, robustness, and speed, PCLIPtools improves the precision of PAR-CLIP data analysis while being accessible to experimental RNA biologists. PCLIPtools can be found on github (https://github.com/paulahsan/pcliptools). Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=76 SRC="FIGDIR/small/688892v1_ufig1.gif" ALT="Figure 1"> View larger version (19K): org.highwire.dtl.DTLVardef@19b32d5org.highwire.dtl.DTLVardef@267a45org.highwire.dtl.DTLVardef@255880org.highwire.dtl.DTLVardef@1d55b60_HPS_FORMAT_FIGEXP M_FIG C_FIG

bioinformatics↗

A human forebrain organoid model phenocopies dysregulated RNA and protein homeostasis in ALS/FTD-associated TDP-43 proteinopathies

TAR DNA-binding protein 43 (TDP-43) proteinopathy is a defining pathological feature of amyotrophic lateral sclerosis (ALS) and frontotemporal dementia (FTD), yet the downstream molecular events linking TDP-43 dysfunction to neurodegeneration remain incompletely understood. Here, we model TDP-43 proteinopathy by introducing the ALS/FTD-associated TARDBP K181E mutation into human induced pluripotent stem cells and differentiating them into three-dimensional forebrain organoids. Organoids carrying the K181E mutation exhibit spontaneous TDP-43 hyperphosphorylation, cytoplasmic p-TDP43 accumulation, RNA dysregulation, pro-inflammatory signaling, and activation of apoptotic pathways without TDP-43 overexpression or external stress. Single-cell transcriptomics and enhanced crosslinking immunoprecipitation reveal that the K181E mutation alters TDP-43 RNA-binding specificity, causing widespread RNA mis-splicing including cryptic exon inclusion. Among affected targets, we identify cryptic exon inclusion in the transcription factor PRDM2. PRDM2 cryptic exon-derived peptide immunoreactivity was detected in ALS spinal motor neurons and associated with p-TDP-43 pathology. These findings identify PRDM2 mis-splicing as a candidate downstream event linking TDP-43 dysfunction relevant to ALS and FTD. One sentence summaryHuman brain organoids reveal how mutant TDP-43 disrupts RNA processing and causes neuronal stress.

neuroscience↗

Dysregulation of U12-Type Splicing in Lupus Neutrophils

ObjectiveNeutrophil dysfunction is a hallmark of systemic lupus erythematosus (SLE), but its molecular basis remains unclear. This study explores transcriptional and post-transcriptional changes in low-density granulocytes (LDGs), a proinflammatory neutrophil subset expanded in SLE, focusing on NADPH oxidase (Nox) function and minor intron splicing. MethodsLDGs and normal-density neutrophils (NDGs) were isolated from SLE patients and healthy controls (HCs). CYBA (P22phox) expression was evaluated at transcript and protein levels. Nox activity was measured using luminol assays. Bulk RNA sequencing and rMATS software were used to assess alternative splicing, particularly of U12-type intron-containing genes. ResultsCYBA expression was reduced in SLE LDGs (n=11) compared to SLE NDGs and HCs (n=6), with levels resembling those in chronic granulomatous disease neutrophils. SLE LDGs exhibited impaired Nox activity (n=7 SLE, n=12 HC). CYBA is a U12 intron-containing gene, and transcriptomic analysis revealed broad downregulation of this gene class in SLE LDGs, suggesting minor spliceosome dysfunction. rMATS analysis showed increased U12-type intron retention and widespread splicing defects-- including exon skipping and mutually exclusive exon use--in genes such as GBP5, MAEA and STX10. These abnormalities were validated in an independent long-read RNA-seq dataset from SLE PBMCs. Importantly, splicing disruptions correlated with disease activity and autoantibody profiles. ConclusionImpaired U12-dependent splicing may contribute to neutrophil dysfunction in SLE, potentially via defective oxidative burst and altered immune regulation. These findings highlight the minor spliceosome as a novel player in lupus pathogenesis.

immunology↗

The DND1-NANOS3 complex shapes the primordial germ cell transcriptome via a heptanucleotide sequence in mRNA 3'UTRs

The RNA-binding proteins DND1 and NANOS3 are essential for primordial germ cell survival1-5. Their co-immunoprecipitation and overlapping loss-of-function phenotypes suggest joint function6-8, yet how they co-regulate target mRNAs remains unclear. Here, we developed Tandem PAR-CLIP and identified a DND1-NANOS3 ribonucleoprotein that specifically recognizes an AUGAAUU heptanucleotide on target mRNAs, termed the NANOS3-dependent DND1 Recognition Element (N3-DRE). mRNAs containing 3'-UTR N3-DREs are aberrantly upregulated in DND1- or NANOS3-deficient germ cells and encode key cell-cycle and epigenome regulators, such as CDK1. Genome editing showed that the N3-DRE is essential for Cdk1 repression in mouse PGCs in vivo. A 1.7-[A] crystal structure of the ternary complex of DND1, NANOS3, and CDK1- N3-DRE RNA revealed a continuous RNA-binding surface that confers high-affinity, sequence- specific recognition. Together, these findings define the molecular and functional basis of N3-DRE-mediated mRNA regulation in germ cell development. Moreover, we provide a paradigm of two RNA-binding proteins with low (DND1) or no (NANOS3) intrinsic sequence-specificity, jointly building a high-information-content RNA sequence motif that is different from the sum of their individual preferences. Because RNA-binding protein specificities are typically studied individually9-13, rather than in the context of ribonucleoproteins, this type of "two-factor authorization" may be an underappreciated mechanism to protect posttranscriptional gene regulatory networks from aberrant expression of an individual ribonucleoprotein component.

molecular biology↗

The MLLT3 YEATS domain is a dual reader of histone marks (H3K9/18/27ac/cr) and ncRNA (7SK), linking epigenetic and RNA signaling to regulate hematopoiesis

The protein MLLT3 (AF9) is a critical regulator of hematopoiesis. The N-terminal YEATS domain of MLLT3 is an epigenetic reader that binds to acetylated as well as crotonylated lysine. Using PAR-CLIP, biochemical assays, and NMR based mapping of binding, we demonstrate that the YEATS domain of MLLT3 binds to a specific stem-loop region of the noncoding RNA 7SK. 7SK is a noncoding RNA with a well-documented function in transcriptional elongation. We developed point mutations in the YEATS domain that disrupt RNA binding while having no effect on binding of acetylated histone peptides to probe the specific role of RNA binding in MLLT3 function. Our results show loss of RNA binding by MLLT3 skews hematopoietic differentiation away from the myeloid lineage and toward the lymphoid lineage and has substantial effects on gene expression, confirming the essential nature of MLLT3-RNA binding for function.

biochemistry↗

Identification of RNA binding proteins that mediate a quality control mechanism of splicing

Accurate splicing, which involves the controlled removal of non-coding sequences (introns) from precursor messenger RNAs (pre-mRNAs), is essential for producing correct mature mRNAs that encode functional proteins. Within pre-mRNAs, latent splice sites (LSSs) resemble proper splice sites but are usually not used because their activation can introduce in-frame STOP codons. The nuclear suppression of splicing (SOS) mechanism prevents the use of LSSs. Although the SOS mechanism is not fully understood, recent studies have identified initiator-tRNA and the NCL protein as key components. To discover additional regulators, we performed a genetic screen targeting RNA-binding proteins (RBPs) with an siRNA library and a luminescence reporter for latent splice site activation. This identified five RBPs -- ALYREF (THOC4), PPIE, DDX41, DHX38, and HNRNPA2B1 -- whose knockdown significantly increased LSS usage in the reporter. RNA-Seq analysis after knocking down each of these RBPs confirmed these results, showing widespread LSS activation in hundreds of mRNAs. Among these, we focused on ALYREF, a conserved protein involved in mRNA export and splicing. Using fPAR-CLIP, we found that U5 snRNA is ALYREFs main binding partner. Overexpressing ALYREF deletion mutants activated latent splicing, and affinity purification confirmed its interaction with U5 snRNA. These mutants exhibited different binding properties, highlighting the importance of specific structural elements within ALYREF in SOS regulation. Our findings reveal that nuclear RBPs play a key role in suppressing LSS activation and suggest that ALYREF has a novel role in maintaining splicing accuracy within the spliceosome, advancing our understanding of the SOS mechanism.

genomics↗

Discovery and therapeutic exploitation of Master Regulatory miRNAs in Glioblastoma

Glioblastoma is a fatal primary malignant brain tumor, with an average survival of only 15 months despite surgical resection, chemotherapy, and radiation therapy. Due to the concurrent deregulation of numerous genes in glioblastoma, molecular monotherapies have not improved clinical outcomes. Evidence suggests that effectively targeting multiple deregulated molecules is essential for better therapies; however, this is limited by the lack of suitable drugs and the increased toxicity of combination therapies. To address this, we hypothesized that miRNAs, small gene-regulatory RNAs that suppress multiple target genes via sequence complementarity, could be developed to inhibit multiple deregulated genes simultaneously, leading to more effective treatments. We identified master regulatory miRNAs--those that target several deregulated genes in glioblastoma--using PAR-CLIP screenings in glioblastoma cells and analyzed TCGA tumor data to find which targets were deregulated. An algorithm ranked these targets based on their significance in glioblastoma malignancy. We selected two tumor suppressor master regulatory miRNAs, miR-340 and miR-382, and one oncogenic miRNA, miR-17. Validation showed that these miRNAs target critical glioblastoma pathways and significantly inhibit cell growth, survival, invasion, and tumor growth in vivo. We developed an innovative therapeutic delivery approach using Brain Penetrating Nanoparticles in combination with MRI-guided focused ultrasound and microbubbles, resulting in reduced tumor volume and extended survival in glioblastoma-bearing mice. This strategy offers a promising pathway for translating miRNA-based therapies into clinical trials for glioblastoma and other cancers. One Sentence SummaryWe developed and used new computational, experimental, and therapeutic approaches to identify and therapeutically deliver master regulatory miRNAs to inhibit the growth of glioblastoma, the most common and deadly primary brain tumor.

cancer biology↗

Effective in vivo RNA base editing via engineered cytidine deaminase APOBECs fused with PUF proteins

Base editing stands at the forefront of genetic engineering, heralding precise genetic modifications with broad implications. While CRISPR-based DNA and RNA base editing systems capitalize on sgRNA-guided specificity and diverse deaminase functionalities, the pursuit of efficient C-to-U RNA editing has been hampered by the inherent constraints of cytidine deaminases. Here, we report an RNA base editing platform by refining cytidine deaminases, termed professional APOBECs (ProAPOBECs), through systematic enhancements and AI-driven protein engineering. ProAPOBECs demonstrate unprecedented catalytic versatility, particularly fused with RNA-recognizing Pumilio and FBF (PUF) proteins. We present the first effective use of RNA base editing in the brain with ProAPOBECs in Mef2c mutant mice, a model for autism. The AAV-mediated RNA base editing via ProAPOBEC not only corrects genetic mutation in mRNAs but significantly alleviates autistic-like behaviors in the mice. This work introduces a pioneering collection of RNA base editing instruments, emphasizing their therapeutic potential in combatting genetic disorders.

molecular biology↗

Determining the off-target activity of antibiotics and novel translation initiation sites in mitochondria

The 13 mtDNA-encoded proteins are synthesized using a dedicated translation system that is more similar to bacterial systems than the cytoplasmic system. Consequently, many bacterial protein synthesis inhibitors, used as antibiotics, exhibit mitochondrial toxicity as off-target effects. However, whether these antibiotics act through the same mechanisms in mitochondria as in bacteria remains unclear. To address this, we characterized the impact of a panel of bacterial translation and elongation inhibitors on mitochondrial translation through mitoribosome profiling. We found that the mechanism of action for every antibiotic, except telithromycin, is the same in both bacteria and mitochondria. Additionally, mitoribosome profiling data showed that MT-ND1 and MT-ND5 have incorrectly annotated translation initiation sites and suggested the presence of several translation initiation sites on ncRNAs that produce mitoribosome footprints, as indicated by the detection of mitoribosome footprints at these locations. This work demonstrates how antibiotics can inhibit mitochondrial translation by mechanisms identically or very similar to those found in bacteria and the utility of mitoribosome profiling for annotating mitochondrial genes.

biochemistry↗

Transformer-based modeling of Clonal Selection and Expression Dynamics (TraCSED) reveals resistance signatures in breast cancer

Understanding transcriptional heterogeneity in cancer cells and its implication for treatment response is critical to identify how resistance occurs and may be targeted. Such heterogeneity can be captured by in vitro studies through clonal barcoding methods. We present TraCSED (Transformer-based modeling of Clonal Selection and Expression Dynamics), a dynamic deep learning approach for modeling clonal selection. Using single-cell gene expression and the fitness of barcoded clones, TraCSED identifies interpretable gene programs and the timepoints at which they are associated with clonal selection. When applied to cells treated with either giredestrant, an estrogen receptor (ER) antagonist and degrader, or palbociclib, a CDK4/6 inhibitor, time-dependent resistance pathways are revealed. For example, ER activity is associated with positive selection around day four under palbociclib treatment and this adaptive response can be suppressed by combining the drugs. Yet, in the combination treatment, one clone still emerged. Clustering based on partial least squares regression found that high baseline expression of both SNHG25 and SNCG genes was the primary marker of positive selection to co-treatment and thus potentially associated with innate resistance - an aspect that traditional differential analysis methods missed. In conclusion, TraCSED enables associating pathways with phenotypes in a time-dependent manner from scRNA-seq data.

cancer biology↗

MATRIN3 deficiency triggers autoinflammation via cGAS-STING activation

Interferon-stimulated genes (ISGs) comprise a program of immune effectors important for host immune defense. When uncontrolled, ISGs play a central role in interferonopathies and other inflammatory diseases. The mechanisms responsible for turning on ISGs are not completely known. By investigating MATRIN3 (MATR3), a nuclear RNA-binding protein mutated in familial ALS, we found that perturbing MATR3 results in elevated expression of ISGs. Using an integrative approach, we elucidate a pathway that leads to activation of cGAS-STING. This outlines a plausible mechanism for pathogenesis in a subset of ALS, and suggests new diagnostic and therapeutic approaches for this fatal disease. One-Sentence SummaryMis-splicing of Tudor Domain Containing 3 (TDRD3) in the absence of MATR3 unleashes R-loops and interferon-stimulated genes.

molecular biology↗

A Multiparametric Analysis Reveals Differential Behavior of Spheroid Cultures on Distinct Ultra-Low Attachment Plates Types

Spheroids have become principal three-dimensional biological models to study cancer, developmental processes, and drug efficacy. For spheroid generation, ultra-low attachment plates are noteworthy due to their simplicity, compatibility with automation, and experimental and commercial accessibility. Nonetheless, it is unknown whether and to what degree the plate type impacts spheroid formation and biology. This study employed automated brightfield microscopy to systematically compare the size and eccentricity of spheroids formed in six different plate types using four distinct human cell lines, i.e., CCD-1137Sk fibroblasts, HaCaT keratinocytes, and MDA-MB-231 and HT-29 cancer cells. Results showed that all plate types exhibited similar sphe-roid-forming capabilities, and the gross patterns of growth or shrinkage during four days after seeding were comparable. Yet, size and eccentricity varied systematically among specific cell lines and plate types. A confocal wholemount analysis by a novel pipeline of AI-based 3D-image analysis procedures revealed changes in cell proliferation, cell number, nuclear volume, and keratino-cyte differentiation, which were accompanied by altered YAP1-signals. The findings show that the plate type may influence the outcome of experimental campaigns. It is advisable to scan different plate types for the optimal configuration for a specific investigation instead of using one standard plate for all kinds of applications.

cancer biology↗