Biology subjects

Dahlin, J. S.

Publications and source records attributed to Dahlin, J. S..

8 recordsLinked to original sources

bioRxiv2026

Modelling human haematopoietic stem cell commitment ex vivo identifies IL-33 as a regulator of megakaryopoiesis

Commitment events to specific blood lineages arise from single hematopoietic stem cells (HSCs) and are influenced by stress, inflammation and disease. However, the understanding of how such events are regulated in human haematopoiesis is limited by the lack of tractable in vitro models. In this study, we introduce a novel Early Progenitor Differentiation (EPD) assay to study the initial lineage commitment of human 49+ HSCs, in a system faithfully recapitulating cell states observed in vivo. Combining single cell -omics approaches and single cell functional assays, we show that IL-33 acts directly on human 49f+ HSCs activating the MAPK pathway to enhance their commitment towards Megakaryocytic-Erythroid-Mast cell Progenitors and subsequently megakaryopoiesis. This occurs without affecting HSC self-renewal via accelerated establishment of chromatin programmes associated with Erythroid and Megakaryocyte and mast cells lineages. Our findings demonstrate the utility of the EPD model to identify molecular regulators of human HSC differentiation and uncover a new role of IL-33 in haematopoiesis.

cell biology↗

bioRxiv2026

Integrated analysis of leukemic mutations and transcriptomes at the single-cell level

Single-cell RNA-sequencing-based characterization of cells that belong to the neoplastic clone is a major challenge in hematologic neoplasms, where malignant and normal cells coexist. Confident molecular profiling requires simultaneous analysis of gene expression and genetic mutations in individual cells, an ability that is not supported by the standard 10X Genomics workflow. Here, we systematically evaluated the potential and limitations of repurposing amplified cDNA generated during the 10X Genomics 3' workflow for post-hoc genotyping of individual cells. We first established a mixed leukemic cell line system comprising one cell line with KIT point mutations and another with the BCR::ABL1 fusion gene. Targeted long-read PacBio sequencing enabled post-hoc assignment of mutation data to transcriptionally profiled cells, but recovery differed between targets. Consistent with ambient RNA in microfluidics-based single-cell workflows, mutation-associated transcripts were detected in cells not expected to carry the corresponding mutations, illustrating how transcript recovery complicates cell-level genotype assignment. Target-specific thresholds mitigated this source of misclassification. In primary chronic myeloid leukemia samples, the post-hoc approach detected BCR::ABL1-positive cells at diagnosis, but not during imatinib treatment. Together, we present a framework for adding mutation status to cells already profiled using the 10X Genomics workflow and highlight broader considerations for transcript-based single-cell genotyping.

cancer biology↗

bioRxiv2025

Single-cell omics-based characterization of human basophils reveals two transcriptionally distinct populations

BackgroundBasophils are implicated in various diseases including allergies, but a comprehensive characterization of human basophils has yet to be performed at the single-cell level. ObjectiveWe aimed to generate a single-cell omics-based resource of circulating human basophils, to be made accessible to the research community. We also sought to investigate basophil heterogeneity at the transcriptional and surface epitope levels. MethodsCirculating basophils were analyzed using short- and long-read single-cell RNA-sequencing in combination with large-scale immunoprofiling of more than 100 cell surface markers. ResultsWe used a cellular indexing of transcriptomes and epitopes by sequencing (CITE-seq) based cell barcoding system to accurately track side scatterlow lineage- CCR3+ Fc{varepsilon}RI+ basophils through the single-cell omics analysis. The approach allowed for accurate transcriptional profiling of basophils among low-density peripheral blood leukocytes. The generation of an additional dataset with only basophils revealed two transcriptionally distinct populations. Single-cell transcriptomic analysis of samples from additional donors was performed and coupled with a large-scale immunoprofiling screen, producing a third CITE-seq dataset containing basophils. The analysis verified the existence of the two transcriptionally distinct populations and revealed that these populations have similar immunophenotypes with regard to the investigated surface markers. Long-read single-cell RNA-sequencing analysis provided further insights into the gene expression dynamics of the circulating basophils and confirmed the transcriptionally defined basophil states. ConclusionsThe single-cell omics analysis revealed two transcriptionally distinct basophil populations. Our single-cell omics resource constitutes a reference for charting human basophils at the cellular and molecular levels in health and disease. Capsule summaryShort- and long-read single-cell RNA-sequencing coupled with large-scale immunoprofiling characterize human basophils in peripheral blood and reveal two transcriptionally distinct populations.

immunology↗

bioRxiv2021

Single-cell transcriptomics reveals the identity and regulators of human mast cell progenitors

Mast cell accumulation is a hallmark of a number of diseases including allergic asthma and systemic mastocytosis. IgE-mediated crosslinking of the Fc{varepsilon}RI receptors causes mast cell activation and contributes to disease pathogenesis. The mast cell lineage is one of the least studied among the hematopoietic cell lineages and there are still controversies about the identity of the mast cell progenitor, i.e., whether Fc{varepsilon}RI expression appears during the hematopoietic progenitor stage or in maturing mast cells. Here, we used single-cell transcriptomics to reveal a temporal association between the appearance of Fc{varepsilon}RI and the mast cell gene signature in CD34+ hematopoietic progenitors. In agreement with these data, the Fc{varepsilon}RI+ hematopoietic progenitors formed morphologically, phenotypically and functionally mature mast cells in long-term culture assays. Single-cell transcriptomics analysis further revealed the expression patterns of prospective cytokine receptors regulating mast cell progenitor development. Culture assays showed that IL-3 and IL-5 promoted disparate effects on progenitor cell proliferation and survival, respectively, whereas IL-33 caused robust Fc{varepsilon}RI downregulation. Taken together, we have demonstrated that Fc{varepsilon}RI appears during the hematopoietic progenitor stage of mast cell differentiation and that external stimuli may regulate the Fc{varepsilon}RI expression. Thus, the results resolve the controversy regarding the appearance of Fc{varepsilon}RI during mast cell development. One-sentence summarySingle-cell analysis of human hematopoiesis uncovers the stage at which Fc{varepsilon}RI appears during mast cell differentiation and reveals disparate effects of IL-3, IL-5 and IL-33 on mast cell progenitor proliferation, survival, and suppression of Fc{varepsilon}RI expression.

cell biology↗

bioRxiv2021

Immunoprofiling reveals novel mast cell receptors and a continuous nature of human lung mast cell heterogeneity

BackgroundImmunohistochemical analysis of granule-associated proteases have revealed that human lungs mast cells constitute a heterogeneous population of cells, with distinct subpopulations identified. However, a systematic and comprehensive analysis of cell surface markers to study human lung mast cell heterogeneity is yet to be performed. MethodsHuman lung mast cells were obtained from lung lobectomies and the expression of 332 cell surface markers were analyzed using flow cytometry and the LEGENDScreen kit. Markers that exhibited a high variance were selected for additional analyses to reveal whether they correlated and if discrete mast cell subpopulations were discernable. ResultsWe identified expression of 102 surface markers on human lung mast cells. Several markers showed a high continuous variation of expression within the mast cell population. Six of these markers correlated: SUSD2, CD49a, CD326, CD34, CD66 and HLA-DR. The expression of these markers also correlated to the size and granularity of the mast cells. However, no marker produced an expression profile consistent with a bi- or multimodal distribution. ConclusionsLEGENDScreen analysis identified more than 100 cell surface markers on mast cells, out of which 23 have to our knowledge not previously described on human mast cells. Several of the newly described markers are known to be involved in sensing the microenvironment, and their identification can shed new light on mast cell functions. The exhaustive expression profiling of the 332 surface markers failed to detect distinct mast cell subpopulations. Instead, we demonstrate a continuous nature of human lung mast cell heterogeneity.

immunology↗

bioRxiv2019

Single-cell molecular profiling provides a high-resolution map of basophil and mast cell differentiation

Differentiation of hematopoietic stem and progenitor cells ensure a continuous supply of mature blood cells. Recent models of differentiation are represented as a landscape, in which individual progenitors traverse a continuum of multipotent cell states before reaching an entry point that marks lineage commitment. Basophils and mast cells have received little attention in these models and their differentiation trajectories are yet to be explored. Here, we have performed multicolor flow cytometry and high-coverage single-cell RNA sequencing analyses to chart the differentiation of hematopoietic progenitors into basophils and mast cells in mouse. Analysis of flow cytometry data reconstructed a detailed map of the differentiation, including a bifurcation of progenitors into two specific trajectories. Molecular profiling and pseudotime ordering of the single cells revealed gene expression changes during differentiation, with temporally separated regulation of mast cell protease genes. We validate that basophil and mast cell signature genes increased along the trajectories into their respective lineage, and we demonstrate how genes critical for each respective lineage are upregulated during the formation of the mature cells. Cell fate assays showed that multicolor flow cytometry and transcriptional profiling successfully predict the bipotent phenotype of a previously uncharacterized population of basophil-mast cell progenitor-like cells in mouse peritoneum. Taken together, we provide a detailed roadmap of basophil and mast cell development through a combination of molecular and functional profiling.

immunology↗

bioRxiv2018

Single-cell analysis reveals the KIT D816V mutation in hematopoietic stem and progenitor cells in systemic mastocytosis

Background: Systemic mastocytosis (SM) is a hematological disease characterized by organ infiltration by neoplastic mast cells. Almost all SM patients have a mutation in the gene encoding the tyrosine kinase receptor KIT causing a D816V substitution and autoactivation of the receptor. Mast cells and CD34+ hematopoietic progenitors can carry the mutation, however, in which progenitor cell subset the mutation arises is unknown. We aimed to investigate the distribution of the D816V mutation in single mast cells and single hematopoietic stem and progenitor cells. Methods: Fluorescence-activated single-cell index sorting and D816V mutation assessment were applied to analyze mast cells and more than 10,000 CD34+ bone marrow progenitors across 10 hematopoietic progenitor subsets. In vitro assays verified cell-forming potential. Findings: We found that in SM 60-99% of the mast cells harbored the D816V mutation. Despite increased frequencies of mast cells in SM patients compared with control subjects, the hematopoietic progenitor subset frequencies were comparable. Nevertheless, the mutation could be detected throughout the hematopoietic landscape of SM patients, from hematopoietic stem cells to more lineage-primed progenitors. In addition, we demonstrate that Fc{varepsilon}RI+ bone marrow progenitors exhibit mast cell-forming potential, and we describe aberrant CD45RA expression on SM mast cells for the first time. Interpretation: The KIT D816V mutation arises in early hematopoietic stem and progenitor cells and the mutation frequency is approaching 100% in mature mast cells, which express the aberrant marker CD45RA.

immunology↗

bioRxiv2017

Graph abstraction reconciles clustering with trajectory inference through a topology preserving map of single cells

Single-cell RNA-seq quantifies biological heterogeneity across both discrete cell types and continuous cell transitions. Partition-based graph abstraction (PAGA) provides an interpretable graph-like map of the arising data manifold, based on estimating connectivity of manifold partitions (https://github.com/theislab/paga). PAGA maps provide interpretable discrete and continuous latent coordinates for both disconnected and continuous structure in data, preserve the global topology of data, allow analyzing data at different resolutions and result in much higher computational efficiency of the typical exploratory data analysis workflow -- one million cells take on the order of a minute, a speedup of 130 times compared to UMAP. We demonstrate the method by inferring structure-rich cell maps with consistent topology across four hematopoietic datasets, confirm the reconstruction of lineage relations of adult planaria and the zebrafish embryo, benchmark computational performance on a neuronal dataset and detect a biological trajectory in one deep-learning processed image dataset.

bioinformatics↗