Biology subjects

Schmauch, E.

Publications and source records attributed to Schmauch, E..

9 recordsLinked to original sources

bioRxiv2026

Length-dependent hypercontractility decoupled from cellular adaptations is the initial phenotype in MYBPC3-haploinsufficient iPSC-derived engineered cardiac tissues

Hypertrophic cardiomyopathy (HCM) is often characterized by a complex landscape of secondary compensatory changes, making it difficult to distinguish primary events triggered by the underlying genetic variants. Here, using patient-derived iPSC-engineered heart tissues cultured in conditions minimizing external stimuli, we identify the initial phenotype of the HCM inducing variant MYBPC3-Q1061X. We demonstrate that initially MYBPC3 haploinsufficiency leads to robust, muscle length-dependent hypercontractility with emerging diastolic dysfunction at higher contraction rates. This phenotype is entirely decoupled from early transcriptional and metabolic stress responses, as evidenced by physiological phenotype and metabolite and cell type-specific transcriptional profiles. Mathematical modeling reveals that the hypercontractile phenotype can be translated to adult cardiac muscle with a small change in myosin availability, amplified by inherent cooperativity within the sarcomere that is instrumental in enhancing the force and the speed of the contraction cycle. Despite the apparent calcium sensitization, these sarcomeric changes do not affect excitation-contraction coupling or calcium buffering in this proximal stage. These results suggest that the primary biophysical defect in MYBPC3-haploinsufficiency manifests as a latent mechanical hypersensitivity that precedes secondary cellular remodeling and functional instability. This initial phenotype provides a window for preventive therapeutic intervention before the onset of permanent cellular remodeling in the heart.

physiology↗

bioRxiv2025

Coordinated circulating and tissue-based T cell responses precede xenograft rejection

Despite the life-saving successes of solid organ transplantation, the number of individuals needing organ transplant far exceeds the number of organs available for use each year. Porcine xenotransplantation, or the use of pig organs for transplantation in people, holds substantial promise but xenograft rejection in humans is poorly understood. T cell rejection by the host immune system is a major challenge for human allografts and may limit the longevity of porcine xenografts. To study the xenograft rejection, we evaluated T cell responses and repertoire dynamics across tissues following porcine thymokidney transplantation in a decedent model over 61 days after bilateral native kidney nephrectomy. Despite induction with anti-thymocyte globulin and ongoing immune suppression consisting of rituximab, corticosteroids, calcineurin inhibition, and mycophenolate mofetil, human T cell infiltration of the xenograft was observed and was associated with xenograft dysfunction. Longitudinal analysis of T cell clonotypes in biopsies of thymokidney revealed accumulation of clonal human CD4 and CD8 T cell responses. Moreover, circulating activated T cells, including circulating T follicular helper (cTfh), were xeno-reactive and increased in frequency around rejection events. We confirmed clonal dominance of a single CD8 clonotype - identified as donor-reactive in a mixed lymphocyte reaction - in the circulation leading up to the acute cellular rejection event. Following re-treatment with anti-thymocyte globulin and intensification of corticosteroids, the T cell clonotypes were dramatically diminished in frequency in thymokidney and lymph nodes, though not eliminated. Over time of observation, the T cell clonotypes were shared across multiple compartments, including xenograft, circulation and lymph nodes and formed clonal families with known xeno-reactive clonotypes, suggesting a coordinated immune response against a limited pool of antigenic targets. Together, these data demonstrate T cell repertoire dynamics across tissues in the setting of xenograft rejection and highlight opportunities for early surveillance, prediction and potential intervention. One-sentence summaryAfter pig-to-human kidney xenotransplantation, xenoreactive T cells form clonotypic families across blood, graft, and lymphoid tissues, indicating a coordinated and targeted response.

immunology↗

bioRxiv2025

Investigating the Intracellular Compartmental Dynamics of miRNAs in Response to Hypoxia

MicroRNAs (miRNAs) are a class of small non-coding RNAs (ncRNAs) with established functions in cytoplasmic gene regulation, where they interact with mRNA transcripts, impeding their translation--a process known as post-transcriptional gene silencing (PTGS). Recent studies have found that miRNAs and other components involved in PTGS are abundantly present in the nucleus of the cells, where they also play important roles in gene regulation. However, the understanding of their function in the nucleus is not well characterized, particularly in response to cellular stress. We conducted nuclear-cytoplasmic fractionation of primary human endothelial cells (ECs) to assess the distribution of miRNAs during hypoxia. The onset of hypoxia led to changes in miRNA expression in both nuclear and cytoplasmic compartments. Notably, a larger proportion of deregulated miRNAs were identified in the nucleus than in the cytoplasm upon hypoxia exposure. We focused on these nuclear-enriched, differentially expressed miRNAs to investigate their cellular functions and their effects on target mRNAs in different compartments. The data indicated a more pronounced alteration in nuclear mRNA expression compared to cytoplasmic expression, pointing towards a nuclear-specific role for these miRNAs. Several miRNAs influenced target mRNAs associated with pathways of cell proliferation and inflammation. Functional assays under hypoxia showed that miR-5091 and miR-7974 reduced EC cell proliferation, while miR-1246 increased it. Additionally, miR-3662 was found to regulate the secretion levels of specific cytokines, impacting the inflammatory response. Overall, our findings highlight the significant role of miRNAs in the nuclear compartment of ECs in modulating the hypoxic response and provide insights into their multifaceted functions.

molecular biology↗

bioRxiv2024

The critical role of isomiRs in accurate differential expression analysis of miRNA-seq data

MicroRNAs (miRNAs) are crucial for the regulation of gene expression and are promising biomarkers and therapeutic targets. miRNA isoforms (isomiRs) differ in their start/end offsets, which can impact the target gene selection and non-canonical function of the miRNA species. In addition, isomiRs frequently differ in their expression patterns from their parent miRNAs, yet their roles and tissue-specific responses are currently understudied, leading to their typical omission in miRNA research. Here, we evaluate the expression differences of isomiRs across conditions and their impact on standard miRNA-seq quantification results. We analyze 28 public miRNA-seq datasets, showing significant expression pattern differences between the isomiRs and their corresponding reference miRNAs, leading to misinterpretation of differential expression signals for both. As a case study, we generate a new dataset assessing isomiR abundance under hypoxia in human endothelial cells between the nuclear and cytosolic compartments. The results suggest that isomiRs are dramatically altered in their nuclear localization in response to hypoxia, indicating a potential non-canonical effect of the species, which would be missed without isomiR-aware analysis. Our results call for a comprehensive re-evaluation of the miRNA-seq analysis practices.

bioinformatics↗

bioRxiv2023

Integrative Multi-omic Profiling of Two Human Decedents Receiving Pig Heart Xenografts Reveals Strong Perturbations in Early Immune-Cell and Cellular Metabolism Responses.

BackgroundRecent advances in xenotransplantation in living and decedent humans using pig xenografts have laid promising groundwork towards future emergency use and first in human trials. Major obstacles remain though, including a lack of knowledge of the genetic incompatibilities between pig donors and human recipients which may led to harmful immune responses against the xenograft or dysregulation of normal physiology. In 2022 two pig heart xenografts were transplanted into two brain-dead human decedents with a minimized immunosuppression regime, primarily to evaluate onset of hyper-acute antibody mediated rejection and sustained xenograft function over 3 days. MethodsWe performed multi-omic profiling to assess the dynamic interactions between the pig and human genomes in the first two pig heart-xenografts transplants into human decedents. To assess global and specific biological changes that may correlate with immune-related outcomes and xenograft function, we generated transcriptomic, lipidomic, proteomic and metabolomics datasets, across blood and tissue samples collected every 6 hours over the 3-day procedures. ResultsSingle-cell datasets in the 3-day pig xenograft-decedent models show dynamic immune activation processes. We observe specific scRNA-seq, snRNA-seq and geospatial transcriptomic changes of early immune-activation leading to pronounced downstream T-cell activity and hallmarks of early antibody mediated rejection (AbMR) and/or ischemia reperfusion injury (IRI) in the first xenograft recipient. Using longitudinal multiomic integrative analyses from blood in addition to antigen presentation pathway enrichment, we also observe in the first xeno-heart recipient significant cellular metabolism and liver damage pathway changes that correlate with profound physiological dysfunction whereas, these signals are not present in the other xenograft recipient. ConclusionsSingle-cell and multiomics approaches reveal fundamental insights into early molecular immune responses indicative of IRI and/or early AbMR in the first human decedent, which was not evident in the conventional histological evaluations.

systems biology↗

bioRxiv2022

QClus: Robust and reliable preprocessing method for human heart snRNA-seq

Single nuclei RNA sequencing (snRNA-seq) remains a challenge for many human tissues, as incomplete removal of background signal masks cell-type-specific signals and interferes with downstream analyses. Here, we present QClus, a droplet-filtering algorithm targeted toward challenging samples, using cardiac tissue as an example. QClus uses specific metrics such as cell-type-specific marker gene expression to cluster nuclei and filter empty and highly contaminated droplets, providing reliable cleaning of samples with varying number of nuclei and contamination levels. In a benchmarking analysis against seven alternative methods across six datasets consisting of 252 samples and over 1.9 million nuclei, QClus achieved the highest quality in the greatest number of samples over all evaluated quality metrics and recorded no processing failures, while robustly retaining numbers of nuclei within the expected range. QClus combines high quality, automation, and robustness with flexibility and user-adjustability, catering to diverse experimental needs and datasets.

genomics↗

bioRxiv2021

Neurons burdened by DNA double strand breaks incite microglia activation through antiviral-like signaling in neurodegeneration.

DNA double strand breaks (DSBs) are linked to aging, neurodegeneration, and senescence1,2. However, the role played by neurons burdened with DSBs in disease-associated neuroinflammation is not well understood. Here, we isolate neurons harboring DSBs from the CK-p25 mouse model of neurodegeneration through fluorescence-activated nuclei sorting (FANS), and characterize their transcriptomes using single-nucleus, bulk, and spatial sequencing techniques. We find that neurons harboring DSBs enter a late-stage DNA damage response marked by the activation of senescent and antiviral-like immune pathways. We identify the NFkB transcription factor as a master regulator of immune gene expression in DSB-bearing neurons, and find that the expression of cytokines like Cxcl10 and Ccl2 develop in DSB-bearing neurons before glial cell types. Alzheimers Disease pathology is significantly associated with immune activation in excitatory neurons, and direct purification of DSB-bearing neurons from Alzheimers Disease brain tissue further validates immune gene upregulation. Spatial transcriptomics reveal that regions of brain tissue dense with DSB-bearing neurons also harbor signatures of inflammatory microglia, which is ameliorated by NFkB knock down in neurons. Inhibition of NFkB or depletion of Ccl2 and Cxcl10 in DSB-bearing neurons also reduces microglial activation in organotypic brain slice culture. In conclusion, we find that in the context of age-associated neurodegenerative disease, DSBs activate immune pathways in neurons, which in turn adopt a senescence associated secretory phenotype to elicit microglia activation. These findings highlight a novel role for neurons in the mechanism of age-associated neuroinflammation. SummaryIt is unclear how age-associated DNA double strand break (DSB) accumulation in neurons influences the progression of cellular senescence and neurodegenerative disease. Here, we leverage mouse models of neurodegeneration, single-nucleus, bulk, and spatial transcriptomics from Alzheimers disease patients, mouse models, and primary neuron cultures to dissect the immune signaling pathways initiated by DSB-bearing neurons that trigger neuroinflammation.

neuroscience↗

bioRxiv2021

isomiRs-specific differential expression is the rule, not the exception: Are we missing hundreds of species in microRNA analysis?

MicroRNAs (miRNAs) are small RNA molecules that act as regulators of gene expression through targeted mRNA degradation. They are involved in many biological and pathophysiological processes and are widely studied as potential biomarkers and therapeutics agents for human diseases, including cardiovascular disorders. Recently discovered isoforms of miRNAs (isomiRs) exist in high quantities and are very diverse. Despite having few differences with their corresponding reference miRNAs, they display specific functions and expression profiles, across tissues and conditions. However, they are still overlooked and understudied, as we lack a comprehensive view on their condition-specific regulation and impact on differential expression analysis. Here, we show that isomiRs can have major effects on differential expression analysis results, as their expression is independent of their host miRNA genes or reference sequences. We present two miRNA-seq datasets from human umbilical vein endothelial cells, and assess isomiR expression in response to senescence and compartment-specificity (nuclear/cytosolic) under hypoxia. We compare three different methods for miRNA analysis, including isomiR-specific analysis, and show that ignoring isomiRs induces major biases in differential expression. Moreover, isomiR analysis permits higher resolution of complex signal dissection, such as the impact of hypoxia on compartment localization, and differential isomiR type enrichments between compartments. Finally, we show important distribution differences across conditions, independently of global miRNA expression signals. Our results raise concerns over the quasi exclusive use of miRNA reference sequences in miRNA-seq processing and experimental assays. We hope that our work will guide future isomiR expression studies, which will correct some biases introduced by golden standard analysis, improving the resolution of such assays and the biological significance of their downstream studies.

bioinformatics↗

bioRxiv2021

Single-cell dissection of live human hearts in ischemic heart disease and heart failure reveals cell-type-specific driver genes and pathways

Ischemic heart disease is globally the leading cause of death. It plays a central role in the electrical and structural remodeling of the right atrium, predisposing to arrhythmias, heart failure, and sudden death. Here, we provide the first dissection of the gene expression changes in the live right atrial tissue, using single-nuclei RNA-seq and spatial transcriptomics. We investigate matched samples of the tissue and pericardial fluid and reveal substantial differences in disease- associated gene expression in all cell types, leading to inflammatory microvascular dysfunction and changes in the tissue composition. Our study demonstrates the importance of creating high- resolution cellular maps and partitioning disease signals beyond epicardial coronary arteries and ischemic left ventricle to identify candidate mechanisms leading to more severe types of human cardiovascular disease. One-Sentence SummarySingle-cell dissection of ex vivo heart biopsies and pericardial fluid in ischemic heart disease and heart failure

molecular biology↗