Biology subjects

Collin, M.

Publications and source records attributed to Collin, M..

9 recordsLinked to original sources

bioRxiv2025

DNMT3A-R882 mutations intrinsically drive dysfunctional neutropoiesis from human haematopoietic stem cells

Clonal haematopoiesis (CH) arises from the expansion of hematopoietic stem cells (HSCs) carrying leukaemia-associated somatic mutations. CH is linked to pathological immune dysregulation and a greater risk of age-related inflammatory diseases. Yet, how CH mutations impact HSC differentiation into immune effector cells remains understudied. Here, we report a single-cell resolution functional and multi-omic investigation of HSC clonal and differentiation dynamics in individuals with DNMT3A-R882 CH. DNMT3A-R882 reshapes the clonal architecture of haematopoiesis towards an aged phylogenetic structure. Functionally, DNMT3A-R882 HSCs produce decreased monocytic output but more abundant and mature neutrophil progeny compared to WT HSCs in the same individual. Whereas DNMT3A-R882 myeloid progenitors display attenuated inflammatory transcriptional programmes, DNMT3A- R882 mature neutrophils acquire proinflammatory and immunomodulatory features typical of maladaptive immunity and CH co-morbidities. Our findings, validated in humanised mice, identify aberrant DNMT3A-R882 HSC-driven neutropoiesis as a key link between CH, immune dysregulation and risk of inflammatory disease.

cell biology↗

bioRxiv2025

Streptococcus pyogenes nuclease A interferes with host complement functions

Bacterial pathogens deploy diverse virulence factors to subvert host immunity, yet the molecular details of these interactions often remain unresolved. Here, we investigate the structure and host interactome of the Streptococcus pyogenes nuclease A (SpnA). We characterized the structure and dynamics of SpnA using hydrogen-deuterium exchange mass spectrometry and single-particle electron cryo microscopy, yielding the first structural insights to this protein. This allowed us to identify an additional oligonucleotide-binding domain whose flexible structure may play an important function in the nucleolytic activity of SpnA. Affinity-pulldown mass spectrometry identified the complement system membrane attack complex C5b67 components as key interactors in human plasma. Cross-linking mass spectrometry combined with integrative modeling identified the direct binding interfaces between SpnA and C5b67. These interfaces are highly conserved among genetically diverse S. pyogenes strains. The interaction between SpnA and C5b67 is suggested to prevent the assembly of a functional membrane attack complex. Taken together, our findings uncover a novel function of SpnA in complement inhibition and identifies new potential targets to prevent and treat S. pyogenes infections.

microbiology↗

bioRxiv2025

Intra-tumoral delivery of FLT3L with CXCR3/CCR5 ligands promotes XCR1+ DC1 infiltration and activates anti-tumor immunity

Tumor infiltration by XCR1 conventional dendritic cells (cDC1) correlates strongly with favorable prognosis and improved responses to immunotherapy. Yet, tumor-driven immunosuppressive programs restrict efficient cDC1 recruitment, highlighting the need for strategies increasing cDC1 access to the tumor microenvironment. Here, we establish a proof-of-concept cell-based immunotherapy that enhances the infiltration of circulating cDC1 progenitors and supports their local expansion. Intratumoral engraftment of autologous mesenchymal stromal cells engineered to express membrane bound FLT3L promotes cDC1 recruitment when combined with poly(I:C). We identify poly(I:C)-induced CXCL9 and CCL5 as essential chemokines controlling intratumoral cDC1 infiltration. Stromal cell-mediated local delivery of FLT3L together with CXCL9 and CCL5 is sufficient to enhance cDC1 infiltration in mice or humanized mice settings. Finally, this approach activates antitumor immunity and partially overcomes resistance to immune checkpoint blockade. Collectively, our data support the therapeutic potential of expanding intratumoral cDC1s through local and sustained delivery of FLT3L, CXCL9, and CCL5.

immunology↗

bioRxiv2021

Epigenetic regulator genes direct lineage switching in MLL-AF4 leukaemia

The fusion gene MLL-AF4 defines a high-risk subtype of pro-B acute lymphoblastic leukaemia. However, relapse can be associated with a switch from acute lymphoblastic to acute myeloid leukaemia. Here we show that these myeloid relapses share oncogene fusion breakpoints with their matched lymphoid presentations and can originate in either early, multipotent progenitors or committed B-cell precursors. Lineage switching is linked to substantial changes in chromatin accessibility and rewiring of transcriptional programmes indicating that the execution and maintenance of lymphoid lineage differentiation is impaired. We show that this subversion is recurrently associated with the dysregulation of repressive chromatin modifiers, notably the nucleosome remodelling and deacetylation complex, NuRD. In addition to mutations, we show differential expression or alternative splicing of NuRD members and other genes is able to reprogram the B lymphoid into a myeloid gene regulatory network. Lineage switching in MLL-AF4 leukaemia is therefore driven and maintained by defunct epigenetic regulation. Statement of SignificanceWe demonstrate diverse cellular origins of lineage switched relapse within MLL-AF4 pro-B acute leukaemia. Irrespective of the developmental origin of relapse, dysregulation of NuRD and/or other epigenetic machinery underpins fundamental lineage reprogramming with profound implications for the increasing use of epitope directed therapies in this high-risk leukaemia.

cancer biology↗

bioRxiv2020

Genomic diversity generated by a transposable element burst in a rice recombinant inbred population

Genomes of all characterized higher eukaryotes harbor examples of transposable element (TE) bursts - the rapid amplification of TE copies throughout a genome. Despite their prevalence, understanding how bursts diversify genomes requires the characterization of actively transposing TEs before insertion sites and structural rearrangements have been obscured by selection acting over evolutionary time. In this study rice recombinant inbred lines (RILs), generated by crossing a bursting accession and the reference Nipponbare accession were exploited to characterize the spread of the very active Ping/mPing family through a small population and the resulting impact on genome diversity. Comparative sequence analysis of 272 individuals led to the identification of over 14,000 new insertions of the mPing miniature inverted-repeat transposable element (MITE) with no evidence for silencing of the transposase-encoding Ping element. In addition to new insertions, Ping-encoded transposase was found to preferentially catalyze the excision of mPing loci tightly linked to a second mPing insertion. Similarly, structural variations, including deletion of rice exons or regulatory regions, were enriched for those with breakpoints at one or both ends of linked mPing elements. Taken together, these results indicate that structural variations are generated during a TE burst as transposase catalyzes both the high copy numbers needed to distribute linked elements throughout the genome and the DNA cuts at the TE ends known to dramatically increase the frequency of recombination. Significance StatementTransposable elements (TEs) represent the largest component of the genomes of higher eukaryotes. Among this component are some TEs that have attained very high copy numbers with hundreds, even thousands of elements. By documenting the spread of mPing elements throughout the genomes of a rice population we demonstrate that such bursts of amplification generate functionally relevant genomic variations upon which selection can act. Specifically, continued mPing amplification increases the number of tightly linked elements that, in turn, increases the frequency of structural variations that appear to be derived from aberrant transposition events. The significance of this finding is that it provides a TE-mediated mechanism that may generate much of the structural variation represented by pan-genomes in plants and other organisms.

genetics↗

bioRxiv2019

Donor monocyte-derived macrophages promote human acute graft versus host disease

Myelopoiesis is invariably present, and contributes to pathology, in animal models of graft versus host disease (GVHD). In humans, a rich inflammatory infiltrate bearing macrophage markers has also been described in histological studies. In order to determine the origin, functional properties and role in pathogenesis of these cells, we isolated single cell suspensions from acute cutaneous GVHD and subjected them to genotype, transcriptome and in vitro functional analysis. A donor-derived population of CD11c+CD14+ cells was the dominant population of all leukocytes in GVHD. Surface phenotype and nanostring gene expression profiling indicated the closest steady-state counterpart of these cells to be monocyte-derived macrophages. In GVHD, however, there was upregulation of monocyte antigens SIRP and S100A8/9, and transcripts associated with leukocyte trafficking, pattern recognition, antigen presentation, and co-stimulation. Isolated GVHD macrophages stimulated greater proliferation and activation of allogeneic T cells, and secreted higher levels of inflammatory cytokines than their steady-state counterparts. In HLA-matched mixed leukocyte reactions, we also observed differentiation of activated macrophages with a similar phenotype. These exhibited cytopathicity to a cell line and mediated pathological damage to skin explants, independently of T cells. Together, these results define the origin, functional properties and potential pathogenic roles of human GVHD macrophages.

immunology↗

bioRxiv2019

A rule-based data-informed cellular consensus map of the human mononuclear phagocyte cell space

Single-cell genomic techniques are opening new avenues to understand the basic units of life. Large international efforts, such as those to derive a Human Cell Atlas, are driving progress in this area; here, cellular map generation is key. To expedite the inevitable iterations of these underlying maps, we have developed a rule-based data-informed approach to build next generation cellular consensus maps. Using the human dendritic-cell and monocyte compartment in peripheral blood as an example, we performed computational integration of previous, partially overlapping maps using an approach we termed backmapping, combined with multi-color flow-cytometry and index sorting-based single-cell RNA-sequencing. Our general strategy can be applied to any atlas generation for humans and other species.\n\nGraphical Abstract\n\nO_FIG O_LINKSMALLFIG WIDTH=200 HEIGHT=110 SRC=\"FIGDIR/small/658179v1_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (18K):\norg.highwire.dtl.DTLVardef@c1b7b2org.highwire.dtl.DTLVardef@32b68org.highwire.dtl.DTLVardef@16e5fcorg.highwire.dtl.DTLVardef@1552028_HPS_FORMAT_FIGEXP M_FIG C_FIG HighlightsO_LIDefining a consensus of the human myeloid cell compartment in peripheral blood\nC_LIO_LI3 monocytes subsets, pDC, cDC1, DC2, DC3 and precursor DC make up the compartment\nC_LIO_LIDistinguish myeloid cell compartment from other cell spaces, e.g. the NK cell space\nC_LIO_LIProviding a generalizable method for building consensus maps for the life sciences\nC_LI

immunology↗

bioRxiv2019

Serum Flt3 ligand is a biomarker of progenitor cell mass and prognosis in acute myeloid leukemia

Fms-like tyrosine kinase 3 (Flt3) is a hematopoietic growth factor receptor expressed on lymphomyeloid progenitors and frequently, by AML blasts. Its ligand, Flt3L, has non-hematopoietic and lymphoid origins, is detectable during homeostasis and increases to high levels in states of hypoplasia due to genetic defects or treatment with cytoreductive agents. Measurement of Flt3L by ELISA reveals that Flt3+AML, is associated with depletion of Flt3L to undetectable levels. After induction chemotherapy, Flt3L is restored in patients entering CR, but remains depressed in those with refractory disease. Weekly sampling reveals marked differences in the kinetics of Flt3L response during the first 6 weeks of treatment, proportionate to the clearance of blasts and cellularity of the BM. In the UK NCRI AML17 trial, Flt3L was measured at day 26 in a subgroup of 135 patients with Flt3 mutation randomized to the tyrosine kinase inhibitor lestaurtinib. In these patients, attainment of CR was associated with higher Flt3L at day 26 (Mann-Whitney p < 0.0001). Day 26 Flt3L was also associated with survival: Flt3L [≤] 291pg/ml was associated with inferior event-free survival; and, Flt3L >1185pg/ml was associated with higher overall survival (p = 0.0119). Serial measurement of Flt3L in patients who had received a hematopoietic stem cell transplant for AML further illustrated the potential value of declining Flt3L to identify relapse. Together these observations suggest that measurement of Flt3L provides a non-invasive estimate of progenitor cell mass in most patients with AML, with the potential to inform clinical decisions.\n\nGraphical abstract\n\nO_FIG O_LINKSMALLFIG WIDTH=151 HEIGHT=200 SRC=\"FIGDIR/small/588319_ufig1.gif\" ALT=\"Figure 1\">\nView larger version (21K):\norg.highwire.dtl.DTLVardef@132f3f3org.highwire.dtl.DTLVardef@2e033eorg.highwire.dtl.DTLVardef@d70598org.highwire.dtl.DTLVardef@b0648a_HPS_FORMAT_FIGEXP M_FIG C_FIG

cancer biology↗

bioRxiv2019

Sweet revenge - Streptococcus pyogenes showcases first example of immune evasion through specific IgG glycan hydrolysis

Streptococcus pyogenes (Group A streptococcus, GAS) is an important human pathogen responsible for a wide variety of diseases from uncomplicated tonsillitis to life-threatening invasive infections. GAS secretes EndoS, an endoglycosidase able to specifically cleave the conserved N-glycan on human IgG antibodies. In vitro, removal of this glycan impairs IgG effector functions but its relevance to GAS infection in vivo is unclear. Using targeted mass spectrometry, we were able to characterize the effects of EndoS on host IgG glycosylation during the course of natural infections in human patients. We found substantial IgG glycan hydrolysis locally at site of infection as well as systemically in the most severe cases. Using these findings we were able to set up appropriate model systems to demonstrate decreased resistance to phagocytic killing of GAS lacking EndoS in vitro, as well as decreased virulence in a mouse model of invasive infection. This study represents the first described example of specific bacterial IgG glycan hydrolysis during infection and highlights the importance of IgG glycan hydrolysis for streptococcal pathogenesis. We thereby offer new insights into the mechanism of immune evasion employed by this pathogen with clear implications for treatment of severe GAS infections and future efforts at vaccine development.

microbiology↗