Jul 2026· Journal of Immunology· Vol 215· 0 citations
TL;DR
Using mice carrying a mutation in the CBFβ2 isoform, it is demonstrated that CBFβ2 haploinsufficiency rewires transcriptional regulatory circuits in adult bone marrow progenitors, rendering them permissive for an early life-restricted Tγδ17 cells.
Abstract
The mammalian immune system develops through a layered process in which successive waves of embryonic hematopoiesis give rise to distinct progenitors that seed and sustain the neonatal and adult immune compartments. The tissue-based early immune system prioritizes barrier protection by constraining inflammation, whereas the adult immune system is optimized for durable pathogen control and memory.
To define the heterogeneity of embryonic precursors that differentiate into immune subsets emerging early in life, we generated a high-resolution single-cell transcriptomic atlas of mouse embryonic hematopoiesis spanning E8.5-E15.5 at 12-hour intervals, encompassing yolk sac, para-aortic-splanchnopleura/aorta-gonad-mesonephros (PsP/AGM), and fetal liver.
The atlas resolved canonical myeloid (including tissue-resident macrophages), lymphoid (including ILC progenitors), and stromal lineages. Moreover, it revealed previously uncharacterized progenitors biased toward innate-like and tissue-resident lymphoid fates. Notably, we identify precursors bearing a Sox13, Atv5, Tcf7, Notch1, Myb and Lef1 gene regulatory module that imposes effector identity to IL-17 secreting γδ T (Tγδ17) cells. These cells also express the CBFβ2-RUNX complex consistent with a pioneer/lineage-competence role. Using mice carrying a mutation in the CBFβ2 isoform, previously shown to be essential for γδ T cell development, we demonstrate that CBFβ2 haploinsufficiency rewires transcriptional regulatory circuits in adult bone marrow progenitors, rendering them permissive for an early life-restricted Tγδ17 cells.
Together, these data provide a reference framework for fetal hematopoiesis and reveal how embryonic gene-regulatory programs encode the foundations of layered immunity.
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Hematopoiesis and Immune System Development (HEM)
Embryonic hematopoiesis is essential for establishing lifelong blood and immune system function. During development, hematopoietic stem and progenitor cells (HSPCs) acquire intrinsic programs that persist into adulthood and can influence disease susceptibility, yet the molecular signals governing these early-life decisions remain poorly understood. Here, we investigated the role of developmental Transforming Growth Factor-β (TGF-β) signaling in regulating HSPC lineage bias and long-term hematopoietic outcomes. Using the zebrafish model, we found that transient embryonic TGF-β signaling inhibition during the HSPC specification window altered their frequency and migration after emergence from the hemogenic endothelium and movement into the key secondary maturation and expansion niche. Single-cell transcriptomic analysis of embryonic HSPCs revealed repression of migration- and cytoskeleton-associated genes alongside dampened expression of myeloid/macrophage-related genes following ALK5 inhibition. Functionally, early ALK5 blockade reduced macrophage numbers and promoted an M2-like immunosuppressive transcriptional profile. These developmental perturbations produced sustained effects on hematopoietic and immune function into adulthood, including diminished inflammatory gene expression, reduced clonal complexity, and impaired regenerative capacity. Together, our findings identify embryonic TGF-β signaling as a key developmental regulator of HSPC fate and immune programming, with potential implications for immune dysfunction and susceptibility to inflammatory-related disease later in life. PAPER HIGHLIGHTS – Transient developmental signaling perturbations reshape hematopoietic trajectories – Embryogenic TGF-β signaling instructs HSPC lineage priming and macrophage specialization – Early HSPC programming establishes persistent inflammatory states, clonal diversity, and modifies regenerative capacity
Marta Mastrogiovanni, Anastasia Nizhnik, Joaquín Cantón-Sandoval et al.· bioRxiv· 0 citations
Drosophila melanogaster offers a genetically tractable model for dissecting the molecular logic of blood cell development. With a simple repertoire of blood cell types, Drosophila hematopoiesis relies on a conserved set of developmental pathways, among which Notch signaling emerges as a central regulator. In this review, we examine how Notch governs successive steps of blood cell development, including the initial specification of hematopoietic progenitors from the cardiogenic mesoderm, niche-dependent progenitor maintenance in the larval lymph gland, and fate decisions that include crystal cell specification, maturation, and transdifferentiation from plasmatocytes. We further address how Notch output is shaped by intracellular trafficking through the endolysosomal pathway, and how metabolic and environmental inputs are integrated to fine-tune lineage specification. Finally, we discuss how attenuation of Notch signaling in progenitors is required to permit lamellocyte differentiation in response to immune challenge. Throughout, we draw comparisons with vertebrate hematopoiesis, identifying conserved regulatory logic in progenitor emergence, niche-mediated stem cell maintenance, and binary fate decisions, while noting species-specific differences that reflect the distinct complexity of each system. Together, these analyses position Notch as a multifunctional developmental regulator whose activity underlies both homeostatic and adaptive blood cell production, and whose dysregulation is linked to hematological malignancies in humans.
Fermín Evangelisti, Pablo Wappner· Developmental Biology· 0 citations
Although early-life immunity was once considered immature, the human fetal immune system is dynamic and compartmentalized by the 2nd trimester. By the 21st gestational week, T lymphocytes dominate the fetal small intestine (SI), yet their mucosal functions prenatally are unclear. Because fetal T cell infiltration is concomitant with rapid intestinal epithelial growth and differentiation in utero, we hypothesized that early-life intestinal T cells support normal mucosal development and function.
We generated an ex vivo co-culture model where SI T cells from fetal or adult donors are integrated with SI organoids, assessing organoid generation and differentiation by microscopy, single-cell RNA sequencing, and multiplexed cytokine assays. To complement our ex vivo approach, we also performed spatial transcriptomics on healthy and diseased SI tissue to investigate T cell-epithelial interactions throughout the human lifespan.
Fetal SI T cells significantly promoted organoid generation and cell cycling gene programs, even in organoids derived from adults or diseased neonates, suggesting they can reprogram the epithelium towards a regenerative state. Uniquely, fetal SI T cells also directed intestinal stem cell (ISC) differentiation towards the secretory lineage. Yet, adult SI T cells did not support organoid growth or differentiation, highlighting specialized roles of fetal T cells. To test whether secreted factors direct ISC fate, we cultured organoids with T cell-derived conditioned media, which was insufficient to stimulate organoid generation. Additionally, fetal SI T cells were significantly more likely to localize near ISCs, supporting the need for physical interactions.
Overall, we report a unique and coordinated developmental program where fetal SI T cells shape ISC programming by balancing growth and differentiation, offering a new therapeutic angle for intestinal diseases where these processes are disrupted.
NIH AI171980, AI179570; NIH P30DK034854-36; YSM Science Fellows 2024 Program and Grant; Yale Department of Pediatrics Trainee Pilot Grant
Mucosal and Regional Immunology (MUC)
Madison S. Strine, Long Phan, Kalida Gawon et al.· Journal of Immunology· 0 citations
Gfi1 regulates endothelial-to-hematopoietic transition (EHT) and hematopoietic stem cell (HSC) maintenance; however, its expression dynamics remain unclear. We generated a non-disruptive Gfi1-T2A-mScarlet reporter to track Gfi1 expression. At E10.5, reporter selectively marked EHT in the dorsal aorta, umbilical artery, and vitelline artery. At E9.5, mScarlet-positive endothelial cells were present in the umbilical and vitelline arteries but were scarce in the dorsal aorta, indicating vascular-bed-specific differences in hemogenic activation. Gfi1 was broadly expressed in fetal liver HSCs, while higher expression levels identified HSCs with enhanced multilineage reconstitution and preferential T-cell output. Although Gfi1 expression declined during fetal-to-adult maturation, a subset of adult bone marrow HSCs retained expression and exhibited superior repopulating and self-renewal capacity. Bulk and single-cell transcriptomic analyses linked this subset to dormant and fetal-associated programs, including imprinted genes. Reduced chromatin accessibility at a conserved Gfi1 +26.5kb putative enhancer correlated with developmental Gfi1 downregulation. Thus, Gfi1 dynamics define EHT onset and functionally distinct HSC stemness.
To date, the identity and maintenance of postnatal thymic epithelial progenitor cells (TEPCs) remain unclear, as does the persistence of bipotent TEPCs after birth or whether lineage-restricted progenitors independently maintain separate TEC compartments. Using an inducible lineage-tracing system based on expression of the thymoproteasomal protein β5t, which is expressed in embryonic and a subset of postnatal TEPCs, we explored the early dynamics of the relationships between thymic epithelial cell (TEC) progenitors and their progeny. Our results identified two potential lineage-biased progenitor subpopulations, distinguished by Ly6d expression. Additionally, we observed that aging disproportionately affects Ly6d− compared to Ly6d+ TEPCs, with implications for rejuvenation of aging thymic epithelia. This study provides insights into the developmental pathways of TEC lineages and their maintenance, contributing to strategies for enhancing thymic function in aging and disease.
Irene Calvo-Asensio, Andreas Tarcevski, Fatima Dhalla et al.· Science Advances· 0 citations
The mouse epidermis harbors two key resident immune populations—dendritic epidermal T cells (DETCs), a subset of invariant γδ T cells, and Langerhans cells (LCs), specialized tissue-resident macrophages—both of which play critical roles in immune surveillance, barrier integrity, and tissue homeostasis. While their fetal origin has been defined, the mechanisms governing their postnatal maturation remain poorly understood. Here, we present a combined immunophenotypic and single-cell transcriptomic map of DETC and LC development from late embryogenesis through adulthood in mice. We delineate distinct differentiation trajectories characterized by dynamic changes in morphology, proliferation, and transcriptional programming. Using γδ T cell deficient mice, we show that LC maturation proceeds independently of canonical γδDETCs, likely due to compensatory αβDETCs. Analysis of germfree mice and wildlings further demonstrates that the postnatal DETC and LC differentiation is independent of microbial colonization. Comparative analysis with developing human epidermis reveals partially conserved differentiation programs. Together, our findings define core principles underlying establishment of the epidermal immune niche.
D. Obwegs, Alexander Oschwald, L. Koetter et al.· Science Advances· 0 citations