Biology subjects

Thomann, S.

Publications and source records attributed to Thomann, S..

4 recordsLinked to original sources

bioRxiv2026

HLiCA: An integrated cell atlas of the healthy human liver

The human liver is composed of a heterogeneous mix of cell types. How these distinct populations contribute individually and collectively to liver function remains poorly understood. Although single-cell technologies have advanced our understanding of liver biology, individual studies have often been limited by small donor cohorts and inconsistent cell type annotations. Integrating multiple datasets can overcome these challenges and better capture biological variability. We present the Human Liver Cell Atlas (HLiCA), an integrated reference of non-disease liver cells assembled from eight datasets across six research centers, encompassing more than 525,000 cells from 110 donors. Developed in collaboration with the Human Cell Atlas Liver Bionetwork, the HLiCA incorporates expert-curated cell annotations refined through community feedback and dedicated cell type annotation meetings. The HLiCA classifies cells into six lineages and expands the cell type resolution to include 47 distinct cell types. Starting from raw sequencing reads, we realigned all data and performed rigorous benchmarking to ensure robust integration across technical and biological variables. Genetic ancestry was inferred for all samples to evaluate the range of ancestral backgrounds represented in the atlas. The expanded cell type annotation enabled identification of previously unrecognized liver cell types, including NRXN1+ stromal cells. Their presence was validated using spatial transcriptomics, which localized NRXN1+ stromal cells to periportal regions. With the number of donors included in the HLiCA we were able to examine cell type specific associations with demographic covariates. In hepatocytes, drug metabolism genes showed differential expression between sexes, and in cholangiocytes, mucus-production genes varied with age. As the largest and most genetically diverse human liver cell atlas to date, the HLiCA provides a comprehensive, well-annotated reference for the field, annotated by expert consensus. This resource will enable deeper interrogation of liver cellular diversity, architecture, and function in the healthy human liver and serve as a reference to understand changes that occur with disease.

genomics↗

bioRxiv2025

An immunobiliary single-cell atlas resolves crosstalk of type 2 cDCs and γδT cells in cholangitis

Background and aimsThe immunobiliary niche serves as a reservoir of tissue-resident immune cells, yet the role of unconventional T cells during cholangitis remains poorly understood. Here, we connect cell state dynamics of type 2 conventional dendritic cells (cDC2) in cholangitis with site-specific{gamma}{delta} T17 responses in liver and draining lymph nodes (LN). MethodsThe 0.1% Diethoxycarbonyl-1,4-Dihydrocollidine (DDC) diet was used to generate an immunobiliary DC- and{gamma}{delta} T-enriched mouse liver and LN single-cell RNA-sequencing (scRNA-seq) atlas covering temporal disease dynamics, resolution and cDC2B depletion. cDC2 trajectories were inferred using VarID2 and{gamma}{delta} T cell transcription factor (TF) regulon activity was predicted by SCENIC. The human biliary niche was resolved by integrating human liver scRNA-seq data with available spatial transcriptomics data. Functional studies were conducted using Tcrd knockout, Il17a/f knockout and Tcrd reporter mice. ResultsA disease trajectory of Mgl2+ cDC2B was identified connecting DC maturation, homing and the expression of Il17-inducing genes. Disease progression was associated with numeric exhaustion of mature cDC2B and recruitment of DC precursors.{gamma}{delta} T cells were the main Il17 producers and were subtyped into Il17ahigh Scart1+ V{gamma}6+ and Il17low Scart2+ V{gamma}4+ populations exhibiting cDC2-directed communication and divergent TF regulon activity. Spatial proximity and conserved molecular interactions of cDC2 and{gamma}{delta} T cells were confirmed in human cholangitis. Il17-deficiency resulted in reduced liver fibrosis in mice, while cDC2B depletion attenuated{gamma}{delta} T17 cell states. ConclusionsIn cholangitis, a profibrogenic function of{gamma}{delta} T cells is contingent on the induction by peribiliary cDC2B, thereby highlighting relevant disease determinants within the immunobiliary and liver-draining LN niche. Impact and ImplicationsThe immunobiliary niche contains rare immune cells such as conventional dendritic cells and unconventional T cells, however, the function of these cell types in liver inflammation remains poorly understood. Mirroring human biliary diseases such as primary sclerosing cholangitis, we induced experimental cholangitis in a mouse model to generate a site-specific single-cell sequencing atlas resource resolving underexplored cell populations. Our data capture a profibrotic hepatic disease state trajectory of Mgl2+ cDC2B inducing a{gamma}{delta} T cell-specific Il17-response, which is attenuated upon cDC2B depletion and in DC precursors, which are characterized by reduced genomic accessibility of{gamma}{delta} T cell-interacting genes. These results highlight the importance of portal niche residing underexplored immune cell populations and the necessity to further resolve immunobiliary niche responses and crosstalk in inflammatory settings such as in cholangitis. Graphical Abstract O_FIG O_LINKSMALLFIG WIDTH=193 HEIGHT=200 SRC="FIGDIR/small/664083v1_ufig1.gif" ALT="Figure 1"> View larger version (49K): org.highwire.dtl.DTLVardef@1d21193org.highwire.dtl.DTLVardef@7ff3dcorg.highwire.dtl.DTLVardef@630c78org.highwire.dtl.DTLVardef@c79f9b_HPS_FORMAT_FIGEXP M_FIG C_FIG

immunology↗

bioRxiv2024

NiCo Identifies Extrinsic Drivers of Cell State Modulation by Niche Covariation Analysis

Cell states are modulated by intrinsic driving forces such as gene expression noise and extrinsic signals from the tissue microenvironment. The distinction between intrinsic and extrinsic cell state determinants is essential for understanding the regulation of cell fate in tissues during development, homeostasis and disease. The rapidly growing availability of single-cell resolution spatial transcriptomics makes it possible to meet this challenge. However, available computational methods to infer topological tissue domains, spatially variable gene expression, or ligand-receptor interactions are limited in capturing cell state changes driven by crosstalk between individual cell types within the same niche. We present NiCo, a computational framework for integrating single-cell resolution spatial transcriptomics with matched single-cell RNA-sequencing reference data to infer the influence of the spatial niche on the cell state. By applying NiCo to mouse embryogenesis, adult small intestine and liver data, we demonstrate the capacity to predict novel niche interactions that govern cell state variation underlying tissue development and homeostasis. In particular, NiCo predicts a feedback mechanism between Kupffer cells and neighboring stellate cells limiting stellate cell activation in the normal liver. NiCo provides a powerful tool to elucidate tissue architecture and to identify drivers of cellular states in local niches.

bioinformatics↗

bioRxiv2020

YAP orchestrates heterotypic endothelial cell communication via HGF/c-MET signaling in liver tumorigenesis

Next to cell autonomous mechanisms, the oncogene yes-associated protein (YAP) controls liver tumor initiation and progression via cell extrinsic functions creating a tumor-supporting environment. However, how YAP affects the microenvironment and in particular the vascular niche, which contributes to liver disease and hepatocarcinogenesis, is poorly understood. In this study, histo-morphological and molecular characterization of murine liver endothelial cells (ECs) populations and human single cell data revealed the presence of liver sinusoidal endothelial cells (LSECs) and capillary endothelial cells (CECs) in healthy liver tissue. In YAPS127A-induced tumorigenesis, a gradual replacement of LSECs by CECs was associated with dynamic changes in the expression of genes involved in EC subtype-specific paracrine communication. The formation of new potential communication hubs connecting CECs and LSECs included the hepatocyte growth factor (Hgf)/c-Met signaling pathway. In hepatocytes and tumor cells, YAP/TEA domain transcription factor 4 (TEAD4)-dependent transcriptional induction of osteopontin (Opn) stimulated c-Met expression in ECs with CEC phenotype, which sensitized these cells to the pro-migratory effects of LSEC-derived Hgf. In human HCCs, the presence of a migration-associated tip-cell signature correlated with poor clinical outcome and the loss of LSEC marker gene expression. In addition, the replacement of LSECs by CECs with exclusive c-MET expression in a CEC subpopulation was confirmed at the single cell level. In summary, YAP-dependent changes of the liver vascular niche comprise the formation of heterologous communication hubs (e.g. the HGF/c-Met axis), in which tumor cell-derived factors modify the crosstalk between LSECs and CECs.

cancer biology↗