Biology subjects

Schell, C.

Publications and source records attributed to Schell, C..

9 recordsLinked to original sources

bioRxiv2026

The microbiome determines the phenotype in CTLA-4 insufficient mice and men

CTLA-4 (haplo)insufficiency displays incomplete penetrance and phenotypic heterogeneity, indicating the involvement of additional disease modifiers beyond the genetic defect. Microbiome analyses reveal a positive association between disease severity and intestinal dysbiosis, highlighting the microbiome as a critical contributor. To investigate this relationship mechanistically, we generated Ctla4/- wildlings harboring a natural microbiota. Unlike specific pathogen free (SPF) counterparts, which remain healthy, Ctla4/- wildlings spontaneously develop disease phenotypes resembling human CTLA-4 haploinsufficiency. Disease onset is followed by reduced microbial diversity and expansion of pathobionts. Integrative immunophenotyping shows that the natural microbiota synergizes with Ctla4 haploinsufficiency to reshape innate and adaptive immune compartments, generating a sustained pro-inflammatory milieu and reduced CTLA-4 expression in the cecum. Furthermore, microbiota-derived metabolites promote inflammatory cytokine production in both murine and human primary T cells via NF-{kappa}B activation. Collectively, Ctla4/- wildlings constitute an effective model for dissecting microbiome-immune crosstalk in CTLA-4 (haplo)insufficiency and for exploring therapeutic strategies.

immunology↗

bioRxiv2026

Fibroblast-derived Collagen VI shapes the structure and function of the tumor-immune microenvironment in clear cell renal cell carcinoma

The importance of the extracellular matrix (ECM) influencing tumor biology in stroma-rich tumors is well established. However, the relevance of individual ECM proteins in rather stroma-poor cancers such as clear cell renal cell carcinoma (ccRCC) is ill-defined. Using bulk proteomics, spatial imaging, and single-cell transcriptomics, we identify collagen VI (COL6) as a predominant ECM component of the ccRCC interstitial stroma, synthesized primarily by fibroblasts and pericytes. Using cell-derived matrix (CDM) models, we demonstrate that COL6 is essential for maintaining an isotropic ECM network architecture and governs the broader matrisomal composition, with direct pro-proliferative consequences for tumor cells both in vitro and in situ. Granular spatial analysis reveals that COL6-rich stromal septa constrain tumor-infiltrating T cells to boundary zones, where CD8+PD1+ phenotypes predominate. Importantly, tyrosine kinase inhibition (TKI) with cabozantinib suppresses COL6 expression in fibroblasts in vitro and in ex vivo tumor models, mirroring COL6-depleted CDM phenotypes. Our findings establish COL6 as a central stromal regulator of ccRCC tumor biology and immune contexture, revealing ECM remodeling as an underappreciated mechanism of TKI action, with implications for combination immunotherapy strategies.

cancer biology↗

bioRxiv2026

Crosstalk between Stromal cells and Macrophages Shapes Host Immunity to Mycobacteria

Granulomas are disease-defining heterocellular tissue structures in mycobacterial infections. They play a multifaceted role ranging from containing the pathogen to causing tissue destruction. Here, we established a mature peritoneal granuloma model in C57BL/6 mice to investigate the dynamic cell-cell interactions during mycobacterial infection, including long-term immune alterations in serous cavities as important sites of disease manifestation. We found that mycobacteria reside in stromal cells, which actively modulate the local tissue environment and shape macrophage responses, particularly through formation of chemokines and colony-stimulating factor 1. Chronic infection induces sustained reprogramming and diversification of stromal cells toward specialized, immune-like states, including active transfer of mycobacteria to macrophages and a pronounced interferon response. Consequently, stromal cells acquire immunoregulatory properties and support pathogen handling, monocyte recruitment and macrophage maturation, thereby playing a decisive role in granuloma formation and thus in the immune response to mycobacteria. HIGHLIGHTSO_LIA novel peritoneal mycobacterial infection model reveals heterocellular crosstalk in mature granulomas. C_LIO_LIMycobacterial infections persistently reshape immune architecture of serous cavities as important disease sites. C_LIO_LIStromal cells act as mycobacterial host cells and acquire immune effector functions. C_LIO_LIStromal cells co-organize the tissue host-pathogen interface by recruiting and directly communicating with bone marrow-derived monocytes. C_LI

immunology↗

bioRxiv2025

Proteomic characterization of sporadic clear cell renal cell carcinoma reveals a matrix-dense pseudocapsule and heterogeneous tumor subtypes

Clear cell renal cell carcinoma (ccRCC) frequently develops a fibrotic pseudocapsule (PC) at the tumor boundary, yet its implications in the disease remain incompletely defined. We performed DIA-based proteomics on formalin-fixed, paraffin-embedded (FFPE) specimens of sporadic ccRCC from 153 patients, comprising 142 tumor, 123 pseudocapsule (PC), and 121 non-malignant adjacent tissue (NAT) samples. The PC displayed a distinctive proteomic signature characterized by matrix accumulation, enhanced remodeling and ECM-cell signaling, consistent with a signaling-competent boundary and active growth factor sequestration rather than a passive fibrotic barrier. Within the tumor, we observed canonical metabolic reprogramming with upregulated glycolysis and hypoxia markers and suppression of aerobic metabolism, accompanied by strong cell-cycle and pro-angiogenic signatures. Immune programs included increased antigen processing and presentation, together with elevated inflammasome and pyroptosis signatures. T-cell markers were enriched in the PC, indicating an immune-active boundary. Among tumors, we identified five distinct proteomic subtypes (C1-C5) spanning proliferative/mitotic, metabolic, immune/EMT/mTOR, and ECM phenotypes. Semi-specific peptide analysis indicated elevated endogenous proteolysis in the tumor and varied across clusters, with C1 and C5 showing the greatest proteolytic burden. Mechanotransduction features showed only modest PC elevation but were dominated by inter-patient variation. The present study defines a matrix-rich, signaling-active pseudocapsule and a classification of heterogeneous tumor subtypes in sporadic ccRCC. The framework provides a compartment-resolved, cluster-informed approach, and it highlights actionable axes of potential clinical relevance.

molecular biology↗

bioRxiv2025

Mycobacterial infection uncovers plasticity of Kupffer cells

Bona fide Kupffer cells (KCs) are prenatally seeded and show unique functional and immunophenotypic features among tissue macrophages. They are considered as terminally differentiated, and adaptability in disease is attributed to recruited, monocyte-derived KCs. Here, we investigated the extent of KC plasticity and the impact of origin in mycobacterial infections that target macrophages and can persist for months. Fate-mapping combined with high-resolution imaging revealed the emergence of a unique, infection specific KC subset which downregulated the signature markers CLEC4F and VSIG4 ("KClow"). KClow were derived from bona fide KCs and located exclusively to granuloma cores. In contrast, monocyte-derived macrophages were contained at the granuloma borders and contributed to this tissue reaction. ATAC and single-cell RNA sequencing identified a specific signature of KClow with high antimycobacterial activity and specialization to a hypoxic microenvironment. Despite their fundamental deviation from the classical KC phenotype, KClow showed remarkable adaptability, and were capable to return to a homeostatic-like KC state. Accordingly, mycobacterial infections unmask KCs as highly plastic cells, capable of responding to extreme environmental changes.

immunology↗

bioRxiv2024

Versatile roles of Annexin A4 in ccRCC: impact on membrane repair, transcriptional signatures, and composition of the tumor microenvironment

Clear cell renal cell carcinoma (ccRCC) is the most prevalent type of renal malignant disease and is characterized by dismal prognosis in the metastasized setting. Invasive growth of cancer cells relates to high levels of compressive forces translating to relevant damage of the plasma membrane. However, functional implications of protein machineries required for plasma membrane repair in ccRCC are not yet completely elucidated. Given the membrane-associated localization of the large family of annexin proteins, we aimed for a global annotation of annexin proteins, which led to the identification of ANXA4 selectively expressed in cancer cells of ccRCC. Interestingly, ANXA4 showed context-dependent distinct localization patterns including the plasma membrane as well as the nuclear compartment/nuclear membrane. We investigated the functional role of ANXA4 in ccRCC employing genetic titration studies (knockdown, CRISPR/Cas9 knockout and overexpression) and identified impaired acute plasma membrane repair as well as invasive capability in conditions of reduced ANXA4 expression. Utilizing computational segmentation of the tumor microenvironment (TME) of ccRCC samples revealed that ANXA4 low tumors exhibited a distinct TME composition compared to ANXA4 high cases. ANXA4 low tumors showed higher levels of tumor infiltrating lymphocytes accompanied by increased deposition of acellular extracellular matrix. Further transcriptomic analysis demonstrated major alterations in transcriptional signatures related to epithelial-mesenchymal transition (EMT) and immune signaling. Transcription factor enrichment analysis and further functional validation identified ELF3 as one central regulator of invasive properties. Our integrative approach including molecular analyses with advanced histopathological segmentation uncovered novel roles for ANXA4 in modulating acute membrane repair, transcriptional regulation, and shaping cellular composition of the ccRCC tumor microenvironment.

cancer biology↗

bioRxiv2024

The Role of the Co-Chaperone DNAJB11 in Polycystic Kidney Disease: Molecular Mechanisms and Cellular Origin of Cyst Formation

Autosomal dominant polycystic kidney disease (ADPKD) is caused by mutations in PKD1 and PKD2, encoding polycystin-1 (PC1) and polycystin-2 (PC2), which are required for the regulation of the renal tubular diameter. Loss of polycystin function results in cyst formation. Atypical forms of ADPKD are caused by mutations in genes encoding endoplasmic reticulum (ER)-resident proteins through mechanisms that are not well understood. Here, we investigate the function of DNAJB11, an ER co-chaperone associated with atypical ADPKD. We generated mouse models with constitutive and conditional Dnajb11 inactivation and Dnajb11-deficient renal epithelial cells to investigate the mechanism underlying autosomal dominant inheritance, the specific cell types driving cyst formation, and molecular mechanisms underlying DNAJB11-dependent polycystic kidney disease. We show that biallelic loss of Dnajb11 causes cystic kidney disease and fibrosis, mirroring human disease characteristics. In contrast to classical ADPKD, cysts predominantly originate from proximal tubules. Cyst formation begins in utero and the timing of Dnajb11 inactivation strongly influences disease severity. Furthermore, we identify impaired PC1 cleavage as a potential mechanism underlying DNAJB11-dependent cyst formation. Proteomic analysis of Dnajb11- and Pkd1-deficient cells reveals common and distinct pathways and dysregulated proteins, providing a foundation to better understand phenotypic differences between different forms of ADPKD.

molecular biology↗

bioRxiv2021

Synuclein alpha accumulation mediates podocyte injury in Fabry nephropathy

Current therapies for Fabry disease are based on reversing intra-cellular accumulation of globotriaosylceramide (Gb3) by enzyme replacement therapy (ERT) or chaperone-mediated stabilization of the defective enzyme, thereby alleviating lysosome dysfunction. However, their effect in the reversal of endorgan damage, like kidney injury and chronic kidney disease remains unclear. First, ultrastructural analysis of serial human kidney biopsies showed that longterm use of ERT reduced Gb3 accumulation in podocytes but did not reverse podocyte injury. Then, a CRISPR/CAS9-mediated -Galactosidase knockout podocyte cell line confirmed ERT-mediated reversal of Gb3 accumulation without resolution of lysosomal dysfunction. Transcriptome-based connectivity mapping and SILAC-based quantitative proteomics identified alpha-synuclein (SNCA) accumulation as a key event mediating podocyte injury. Genetic and pharmacological inhibition of SNCA improved lysosomal structure and function in Fabry podocytes, exceeding the benefits of ERT. Together, this work reconceptualizes Fabry-associated cell injury beyond Gb3 accumulation, and introduces SNCA modulation as a potential intervention, especially for patients with Fabry nephropathy.

molecular biology↗

bioRxiv2021

Persistence and expansion of cryptic endangered red wolf genomic ancestry along the American Gulf coast

Admixture and introgression play a critical role in adaptation and genetic rescue that has only recently gained a deeper appreciation. Here, we explored the geographic and genomic landscape of cryptic ancestry of the endangered red wolf that persists within the genome of a ubiquitous sister taxon, the coyote, all the while the red wolf has been extinct in the wild since the early 1980s. We assessed admixture across 102,621 SNP loci genotyped in 293 canid genomes. We found support for increased red wolf ancestry along an east-to-west gradient across the southern United States that was associated with historical admixture in the past 100 years. Southwestern Louisiana and southeastern Texas, the geographic zone where the last red wolves were known prior to their extinction in the wild, contained the highest and oldest levels of red wolf ancestry. X-linked regions of low recombination rates were depleted of introgression, relative to the autosomes, suggestive of the large X effect and enrichment with loci involved in maintaining reproductive isolation. Recombination rate was positively correlated with red wolf ancestry across coyote genomes, consistent with theoretical predictions. The geographic and genomic extent of cryptic red wolf ancestry can provide novel and variable genomic resources for the survival of the endangered red wolf.

evolutionary biology↗