Biology subjects

Steinmetz, L.

Publications and source records attributed to Steinmetz, L..

10 recordsLinked to original sources

bioRxiv2026

Damaging RBM20 E-rich domain variants are not rescued by gene replacement

The promise of precision therapeutics in genetic cardiomyopathies relies on linking specific therapies to variant mechanisms. Missense variants in the cardiac splice regulator RBM20 cause a highly penetrant and arrhythmogenic dilated cardiomyopathy. Disease-causing variants in RBM20s arginine-serine rich (RS) domain act via formation of toxic gain of function cytoplasmic granules, but this is not true for a small number of clinically adjudicated pathogenic variants in its glutamate(E)-rich domain. To better define the effects of E-rich domain variants, we developed a scalable screen based on induced pluripotent stem cell (iPSC) cardiomyocyte differentiation that identified several additional damaging variants. Several of these reduced RBM20 protein abundance and stability. We therefore hypothesized that, unlike RS domain variants, these E-rich variants might be rescued by RBM20 overexpression. To test this hypothesis, we generated induced pluripotent stem cells (iPSCs) from a patient with a pathogenic E-rich domain variant (p.E913K), and confirmed reduced RBM20 protein expression in these RBM20+/p.E913K cells after differentiation to iPSC-derived cardiomyocytes (iPSC-CM, vs. engineered isogenic RBM20+/+). These iPSC-CMs also displayed aberrant transcriptional splicing, reduced contractility, increased calcium-induced calcium release, and nuclear localization of RBM20 protein, often with more than the two expected RBM20-centric splice factories. AAV-based overexpression of RBM20 reversed some, but not all of the mis-splicing events identified in RBM20+/p.E913K iPSC-CMs, and did not improve their abnormal contractility, calcium handling or supernumerary RBM20 nuclear granules. In summary, our data indicate that pathogenic E-rich domain variants reduce RBM20 protein abundance, but that their mechanism is unlikely to be explained by haploinsufficiency alone.

genetics↗

bioRxiv2026

Disruption of RBM20 causes atrial electrophysiological disturbances

BackgroundDilated cardiomyopathy (DCM) is a leading cause of heart failure, with 30-50 % of cases attributed to familial inheritance. Mutations in RNA-binding motif protein 20 (RBM20) account for 3-5 % of cases and are associated with severe DCM and ventricular arrhythmias. However, the role of RBM20 mutations in atrial cardiomyopathy (AtCM) and atrial fibrillation (AF) remains underexplored. This study investigates the effects of the RBM20-R636Q mutation on atrial electrophysiology and evaluates sodium-glucose co-transporter (SGLT) inhibitors as potential therapeutics. ResultsRbm20-R636Q mice exhibited atrial remodeling, including hypertrophy, left atrial enlargement, and shortened action potential duration at 90% repolarization (APD90). Compared with RBM20-knockout and laminopathy models, RBM20-R636Q mice showed distinct reductions in Ito / IKur without changes in IK,sus or IK,tail currents, alongside TASK-1 potassium current upregulation and alterations of ICaL. SGLT inhibitors (sotagliflozin, empagliflozin, dapagliflozin) reduced AP inducibility and partially restored APD90, with effects comparable to lidocaine, suggesting a role in modulating peak sodium currents. ConclusionsRBM20 mutations contribute to atrial remodeling, promoting AtCM and AF. SGLT inhibitors demonstrate therapeutic potential by modulating atrial electrophysiology and reducing arrhythmogenesis, offering a promising strategy for managing RBM20-related cardiac disorders. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=156 SRC="FIGDIR/small/711772v1_ufig1.gif" ALT="Figure 1"> View larger version (46K): org.highwire.dtl.DTLVardef@7bcccaorg.highwire.dtl.DTLVardef@1c20b0dorg.highwire.dtl.DTLVardef@63bbcdorg.highwire.dtl.DTLVardef@1bea67f_HPS_FORMAT_FIGEXP M_FIG C_FIG

molecular biology↗

bioRxiv2025

Innate immune responses to Plasmodium falciparum disrupt the blood-brain barrier

Plasmodium falciparum accumulation at the blood-brain barrier (BBB) is a hallmark of cerebral malaria, a life-threatening complication. Conversely, the contribution of the immune response to vascular injury has long been debated. Here, we studied the role of innate immune cells as potential effectors of vascular damage using a human in vitro 3D-BBB model. Parasite-stimulated immune cells from malaria-naive donors increased adhesion to microvessels, at least partly through LFA-1. This caused barrier disruption and inflammatory activation of BBB cells. Secretion of TNF-, IFN-{gamma}, and granzyme B by monocytes, NK and {gamma}{delta} T cells correlated with vascular injury, and accumulation of immune cells was required for local barrier damage. Our computational analysis disentangled pathogenic mechanisms driven specifically by either P. falciparum parasite or immune cells, as well as shared pathways. These findings demonstrate how vascular-immune interactions may contribute to vascular injury in cerebral malaria and point towards the potential of immunomodulatory therapeutics.

immunology↗

bioRxiv2024

Perturbation-driven transcriptional heterogeneity impacts cell fitness

Heterogeneity is inherent to living organisms and it determines cell fate and phenotypic variability1-3. Indeed, even isogenic cell populations vary in quantifiable phenotypes. Here we generated a high-resolution single-cell yeast transcriptome atlas using genotype and clone RNA barcoded deletions to profile 3500 mutants under control and stress conditions in a genome-scale genetic and environmental perturbation screen. We uncovered a myriad of cell states within a population with specific transcriptional architectures that are both intrinsically and extrinsically regulated, thereby suggesting a continuum of cell states. Cell state occupancy and transition can be genetically modulated with specific mutants that act as state attractors, resulting in differential fitness. By exploiting the power of intra-genetic variability, we identified regulators of transcriptional heterogeneity that are functionally diverse and influenced by the environment. One-Sentence SummaryThe yeast single cell-transcriptome atlas based on RNA-traceable genetic perturbations served to map cellular states and define their underlying genetic basis.

genetics↗

bioRxiv2024

Integration of genetic and epigenetic data pinpoints autoimmune specific remodelling of enhancer landscape in CD4+ T cells

CD4+ T cells play a crucial role in adaptive immune responses and have been implicated in the pathogenesis of autoimmune diseases (ADs). Despite numerous studies, the molecular mechanisms underlying T cell dysregulation in ADs remain incompletely understood. Here, we used transcriptomic and epigenomic data from CD4+ T cells of healthy donors and patients with systemic lupus erythematosus (SLE), psoriasis, juvenile idiopathic arthritis (JIA), and Graves disease to investigate the role of enhancers in AD pathogenesis. By generating enhancer-based gene regulatory networks (eGRNs), we identified disease-specific dysregulated pathways and potential downstream target genes of enhancers harbouring AD-associated single-nucleotide polymorphisms, which we also validated using CRISPRi in primary CD4+ T cells. Our results suggest that alterations in the regulatory landscapes of CD4+ T cells, including enhancers, contribute to the development of ADs and provide a basis for developing new therapeutic approaches.

genomics↗

bioRxiv2023

A scalable, GMP-compatible, autologous organotypic cell therapy for Dystrophic Epidermolysis Bullosa

BackgroundGene editing in induced pluripotent stem (iPS) cells has been hailed to enable new cell therapies for various monogenetic diseases including dystrophic epidermolysis bullosa (DEB). However, manufacturing, efficacy and safety roadblocks have limited the development of genetically corrected, autologous iPS cell-based therapies. MethodsWe developed Dystrophic Epidermolysis Bullosa Cell Therapy (DEBCT), a new generation GMP-compatible (cGMP), reproducible, and scalable platform to produce autologous clinical-grade iPS cell-derived organotypic induced skin composite (iSC) grafts to treat incurable wounds of patients lacking type VII collagen (C7). DEBCT uses a combined high-efficiency reprogramming and CRISPR-based genetic correction single step to generate genome scar- free, COL7A1 corrected clonal iPS cells from primary patient fibroblasts. Validated iPS cells are converted into epidermal, dermal and melanocyte progenitors with a novel 2D organoid differentiation protocol, followed by CD49f enrichment and expansion to minimize maturation heterogeneity. iSC product characterization by single cell transcriptomics was followed by mouse xenografting for disease correcting activity at 1 month and toxicology analysis at 1-6 months. Culture-acquired mutations, potential CRISPR-off targets, and cancer-driver variants were evaluated by targeted and whole genome sequencing. FindingsiPS cell-derived iSC grafts were reproducibly generated from four recessive DEB patients with different pathogenic mutations. Organotypic iSC grafts onto immune-compromised mice developed into stable stratified skin with functional C7 restoration. Single cell transcriptomic characterization of iSCs revealed prominent holoclone stem cell signatures in keratinocytes and the recently described Gibbin-dependent signature in dermal fibroblasts. The latter correlated with enhanced graftability. Multiple orthogonal sequencing and subsequent computational approaches identified random and non-oncogenic mutations introduced by the manufacturing process. Toxicology revealed no detectable tumors after 3-6 months in DEBCT- treated mice. InterpretationDEBCT successfully overcomes previous roadblocks and represents a robust, scalable, and safe cGMP manufacturing platform for production of a CRISPR-corrected autologous organotypic skin graft to heal DEB patient wounds.

bioengineering↗

bioRxiv2021

Human KIR+CD8+ T cells target pathogenic T cells in Celiac disease and are active in autoimmune diseases and COVID-19

Previous reports show that Ly49+CD8+ T cells can suppress autoimmunity in mouse models of autoimmune diseases. Here we find a markedly increased frequency of CD8+ T cells expressing inhibitory Killer cell Immunoglobulin like Receptors (KIR), the human equivalent of the Ly49 family, in the blood and inflamed tissues of various autoimmune diseases. Moreover, KIR+CD8+ T cells can efficiently eliminate pathogenic gliadin-specific CD4+ T cells from Celiac disease (CeD) patients leukocytes in vitro. Furthermore, we observe elevated levels of KIR+CD8+ T cells, but not CD4+ regulatory T cells, in COVID-19 and influenza-infected patients, and this correlates with disease severity and vasculitis in COVID-19. Expanded KIR+CD8+ T cells from these different diseases display shared phenotypes and similar T cell receptor sequences. These results characterize a regulatory CD8+ T cell subset in humans, broadly active in both autoimmune and infectious diseases, which we hypothesize functions to control self-reactive or otherwise pathogenic T cells. One-Sentence SummaryHere we identified KIR+CD8+ T cells as a regulatory CD8+ T cell subset in humans that suppresses self-reactive or otherwise pathogenic CD4+ T cells.

immunology↗

bioRxiv2021

Survey data on European organic multi-species livestock farms

While there is increasing evidence of the sustainability benefits of diversified systems in the organic cropping sector, this has been much less investigated with organic livestock farming. To fill this knowledge gap, we surveyed a sample of 128 European organic multi-species livestock farms located across seven countries - Austria, Belgium, France, Germany, Italy, Sweden and Switzerland - and covering a large range of livestock species combinations. We recorded 1574 variables as raw data out of which we calculated 107 indicators describing farm structure, management and several sustainability dimensions: resource use efficiency and conservation, animal, land and work productivities, animal and human welfare. After technical validation of the data, we withdrew 26 farms and the database covers 102 farms. This database is well suited to unveil relationships between various dimensions of organic multi-species livestock farm sustainability and their structure and management. It can help reveal sustainable strategies for organic multi-species livestock farming systems and understand levers or barriers to their development.

ecology↗

bioRxiv2018

Condensin controls cellular RNA levels through the accurate segregation of chromosomes instead of directly regulating transcription

Condensins are genome organisers that shape chromosomes and promote their accurate transmission. Several studies have also implicated condensins in gene expression, although the mechanisms have remained enigmatic. Here, we report on the role of condensin in gene expression in fission and budding yeasts. In contrast to previous studies, we provide compelling evidence that condensin plays no direct role in the maintenance of the transcriptome, neither during interphase nor during mitosis. We further show that the changes in gene expression in post-mitotic fission yeast cells that result from condensin inactivation are largely a consequence of chromosome missegregation during anaphase, which notably depletes the RNA-exosome from daughter cells. Crucially, preventing karyotype abnormalities in daughter cells restores a normal transcriptome despite condensin inactivation. Thus, chromosome instability, rather than a direct role of condensin in the transcription process, changes gene expression. This knowledge challenges the concept of gene regulation by canonical condensin complexes.

molecular biology↗

bioRxiv2017

Gene fusion between CDKN1A and RAB44 caused by exon skipping like mechanism due to disruption of a splice site

Splicing contributes to gene regulation and protein diversity, while abnormal splicing underlies both hereditary diseases and cancers. Various mutations that disrupt splicing factors, exonic or intronic splicing enhancers or silencers, as well as splice sites, could be responsible for abnormal splicing. Characterization of abnormal splicing events is not only helpful for understanding the molecular processes linking mutations to disease phenotypes, but also provides promising targets for targeted therapies. In addition, CRISPR/Cas9 editing could be benefited once more attention is given to potential abnormal splicing outcomes other than off-target effects at the DNA level. Although large-scale multiplexed genome editing has been demonstrated in yeast, and has also been attempted for particular exons or genes in other eukaryotic cells to achieve saturation, in practice it is much more difficult to measure splicing consequences with genome-wide saturation editing in human cells. Instead, massive somatic mutations accumulated in cancer cohorts provide invaluable opportunities to study somatic mutation-associated splicing events. Abnormal splicing is not necessarily limited to single genes. Transcript fusion is a special form of abnormal splicing that connects two or more genes due to splicing on a transcriptional level (rather than chromosomal translocations such as BCR-ABL in chronic myeloid leukemia). It could arise from conventional splicing on read-through transcripts when the two genes are next to each other and on the same strand, or from trans-splicing when two genes are on different chromosomes, strands or far away - a few cases had been reported. However, it was found that these fusions not only occurred in tumors but also in normal tissues; there was limited investigation regarding how the fusion could happen, whether it be due to mutations or not, and what the downstream perturbations were. Here, in an effort to characterize somatic mutation-associated abnormal splicing (especially in its simplest form, exon skipping events), we identified over one hundred such events in various tumors, including those in MET, PTEN and TP53. Surprisingly, we detected a recurrent, but previously undescribed, tumor-specific transcript fusion event between the cyclin-dependent kinase inhibitor CDKN1A and the RAS oncogene family gene RAB44. By creating genome-edited cell lines, we demonstrate a causal relationship between splice-site mutations in CDKN1A and the fusion to the RAB44 transcript. We further provide evidence that the fusion arises from a readthrough transcript that escapes exosome-mediated degradation when the splice-site mutation occurred, and we show that the presence of the fusion transcript correlates with TP53 inactivation and CDK activation. The strong tissue specificity of RAB44 and the relatively high prevalence of this transcript fusion in multiple types of cancers warrants further study which could inform subclassifications of these cancers and the development of targeted therapies.

genetics↗