Biology subjects

Azzoni, E.

Publications and source records attributed to Azzoni, E..

6 recordsLinked to original sources

bioRxiv2026

The Aorta-Gonad-Mesonephros niche shapes the functions of yolk sac-derived macrophages involved in hematopoietic stem and progenitor cell generation ex vivo

Hematopoietic stem cells (HSCs) generated from induced pluripotent stem cells (iPSCs) offer a promising patient-specific alternative to allogeneic transplantation, yet current differentiation protocols fail to fully recapitulate in vivo HSC maturation. During mouse development, yolk sac (YS)-derived macrophages populate the aorta-gonad-mesonephros (AGM) region at the time of HSC emergence, but the mechanisms by which they support ex vivo hematopoietic stem and progenitor cell (HSPC) generation remain poorly defined. Bulk RNA sequencing revealed that mature AGM CD206 macrophages upregulate pro-inflammatory cytokines and the adhesion molecule F4/80. Using F4/80 knockout embryos, we identify a previously unreported, niche-specific role for F4/80 in restraining the frequency and colony-forming activity of HSPC subsets in the AGM, while supporting endothelial cell maintenance; this effect was absent in the YS. Lineage-tracing with a Cdh5-CreERT2;Rosa26LSL-tdTomato pulse-chase system confirmed that both CD206 and CD206- AGM cells originate from early YS-derived endothelial precursors, with no evidence of local macrophage generation within the AGM. Functional co-culture assays further demonstrated that the ability of CD206 macrophages to enhance the progenitor potential of hemogenic endothelium is AGM-specific and not an intrinsic, ontogeny-determined property, as YS macrophages failed to confer the same benefit even when paired with AGM endothelial cells, and AGM macrophages were ineffective with YS endothelium. Differential expression and NicheNet ligand-receptor interaction analyses identified a small set of AGM-restricted macrophage genes - including Mmp2, Nrep, Ccl2, and Cxcl16 - which are predicted to interact with both endothelial and cluster cells during endothelial-to-hematopoietic transition. Together, these findings establish that AGM macrophages acquire niche-specific transcriptional and functional properties upon entry into the aortic microenvironment, independent of their YS origin, and identify candidate macrophage-derived factors and a novel regulatory role for F4/80 in shaping HSPC output. These insights may guide the refinement of iPSC-based HSC differentiation protocols through the targeted, temporally controlled addition of macrophage-associated signals.

developmental biology↗

bioRxiv2025

Resolving hematopoietic stem versus progenitor cell potential in the mouse dorsal aorta by differential Runx1 +110 enhancer activity

Hematopoietic stem cells (HSCs) are important in cell-based therapies for blood-related disorders. While progress has been made in the directed differentiation of pluripotent PSCs, such cultures promote hematopoietic progenitor cells (HPCs) over HSCs. Thus, elucidating signals, factors, and markers associated with HSC versus HPC lineage development in the embryo is imperative. During mouse embryonic development, HSCs and HPCs originate from hemogenic endothelium (HE) through a process critically dependent on the transcription factor Runx1. Here, we identified a Runx1 enhancer that distinguishes emerging dorsal aorta HSCs from HPCs. Phenotypic, functional, and transcriptomic analyses of Runx1 +110 enhancer-GFP reporter (110GFP) transgenic embryos showed that 110GFP expression marks HPCs, but not the emerging HSC lineage. Comparative transcriptomics revealed a 17-gene signature associated with in vivo long-term HSC potential. Furthermore, 110GFP- preHSCs showed increased expression of Jarid2 and other PRC2 components, suggesting a role for epigenetic regulation in establishing the HSC fate during EHT. Finally, single-cell multiome analysis of dorsal aorta EHT identified the Runx1 +3 enhancer as preferentially accessible in preHSC and underlined the specific activity of the +110 enhancer in HPCs. Our study demonstrates the power of cell-type specific enhancer-reporter models to dissect cell fate decisions in development and provides new inroads to label and/or perturb HSC versus HPC fate decisions in vivo and in vitro.

developmental biology↗

bioRxiv2025

MICROGLIAL EXTRACELLULAR VESICLES MEDIATE C1Q DEPOSITION AT THE PRE-SYNAPSE AND PROMOTE SYNAPTIC PRUNING

C1q is released by microglia, localizes on weak synapses and acts as a tag for microglial synaptic pruning. However, how C1q tags synapses during the pruning period remains to be fully elucidated. Here, we report that C1q is delivered by microglia to pre-synaptic sites that externalize phosphatidylserine through extracellular vesicles. Using approaches to increase or reduce vesicles production in microglia, by C9orf72 knock out or pharmacological inhibition respectively, we provided mechanistic evidence linking extracellular vesicle release to pre-synaptic remodelling in neuron-microglia cultures. In C9orf72 knockout mice, we confirmed larger production of microglial extracellular vesicles, and showed augmented C1q presynaptic deposition associated with enhanced engulfment by microglia in the early postnatal hippocampus. Finally, we provide evidence that microglia physiologically release more vesicles during the period of postnatal circuit refinement. These findings implicate abnormal release of microglial extracellular vesicles in both neurodevelopmental and age-related disorders characterized by dysregulated microglia-mediated synaptic pruning.

neuroscience↗

bioRxiv2024

Hemogenic endothelium of the vitelline and umbilical arteries is the major contributor to mouse fetal lympho-myelopoiesis

Embryonic hematopoiesis consists of distinct waves originating in rapid succession from different anatomical locations. Hematopoietic progenitors appearing earlier than definitive hematopoietic stem cells (HSCs) play key roles in fetal and postnatal life. However, their precise origin, identity and the extent of their contribution need further clarification. To this aim, we took advantage of a genetic fate-mapping strategy in mice that allows labeling and tracking of distinct subsets of hemogenic endothelium (HE). Time-course labeling of hematopoietic progenitors emerging from HE between E8.5 and E9.5, before intra-embryonic definitive HSC generation, revealed a major fetal lympho-myeloid contribution which declined in the adult. Lineage tracing coupled with whole-mount imaging and single-cell RNA sequencing located its source within hematopoietic clusters of vitelline and umbilical arteries. Functional assays confirmed the transient nature of these progenitors. We therefore unveiled a hitherto unidentified early wave of fetal-restricted hematopoietic stem/progenitor cells poised for differentiation that provide a major contribution to pre-natal hematopoiesis.

developmental biology↗

bioRxiv2023

Spatiotemporal dynamics of cytokines expression dictate fetal liver hematopoiesis.

During embryogenesis, yolk-sac and intra-embryonic-derived hematopoietic progenitors, comprising the precursors of adult hematopoietic stem cells, converge into the fetal liver. With a new staining strategy, we defined all non-hematopoietic components of the fetal liver and found that hepatoblasts are the major producers of hematopoietic growth factors. We identified mesothelial cells, a novel component of the stromal compartment, producing Kit ligand, a major hematopoietic cytokine. A high-definition imaging dataset analyzed using a deep-learning based pipeline allowed the unambiguous identification of hematopoietic and stromal populations, and enabled determining a neighboring network composition, at the single cell resolution. Throughout active hematopoiesis, progenitors preferentially associate with hepatoblasts, but not with stellate or endothelial cells. We found that, unlike yolk sac-derived progenitors, intra-embryonic progenitors respond to a chemokine gradient created by CXCL12-producing stellate cells. These results revealed that FL hematopoiesis is a spatiotemporal dynamic process, defined by an environment characterized by low cytokine concentrations.

developmental biology↗

bioRxiv2022

Balanced SET levels favor the correct enhancer repertoire during cell fate acquisition

Within the chromatin, distal elements interact with promoters to regulate specific transcriptional programs. Histone acetylation, interfering with the net charges of the nucleosomes, is a key player in this regulation. Here, we report that the onco-protein SET is a critical determinant for the levels of histone acetylation within enhancers. We disclose that conditions in which SET is accumulated, including the severe Schinzel-Giedion Syndrome (SGS), are characterized by a failure in the usage of the distal regulatory regions typically employed during fate commitment. This is accompanied by the usage of alternative enhancers leading to a massive rewiring of the distal control of the gene transcription. This represents a (mal)adaptive mechanism that, on one side, allows to achieve a certain degree of differentiation, while on the other affects the fine and corrected maturation of the cells. Thus, we propose the differential in cis-regulation as a contributing factor to the pathological basis of the SET-related disorders in humans, including SGS, neurodevelopmental disorders, myeloproliferative diseases, and cancer.

developmental biology↗