About

Nancy A. Speck, Ph.D., is the John W. Eckman Professor in Medical Science II at the University of Pennsylvania's Perelman School of Medicine. She is an investigator at the Abramson Family Cancer Research Institute, a member of the Abramson Cancer Center, and a member of the Institute for Regenerative Medicine. Dr. Speck serves as the Chair of the Department of Cell and Developmental Biology. Her research centers on the roles of the core binding factor (Runx1-CBFβ) in hematopoietic stem cell (HSC) formation and function, as well as its implications in leukemia. She studies how HSCs form during embryonic development, focusing on the transition from hemogenic endothelium to pre-HSCs and then to fully functional adult HSCs. Her work has demonstrated the critical role of Runx1 in blood formation, the heterogeneity of hemogenic endothelium, and the influence of inflammatory signaling in HSC development. Additionally, Dr. Speck investigates how mutations in Runx1 contribute to pre-leukemic stem cells and leukemia progression, particularly through effects on ribosome biogenesis and cellular stress responses. Her contributions have helped clarify the molecular mechanisms underlying hematopoietic development and leukemogenesis.

Research topics

• Biology
• Cell biology
• Molecular biology
• Immunology
• Cancer research

Selected publications

• Update of germline RUNX1 variant curation rules: version 3.1

  Blood Advances · 2026-04-22

  articleOpen access
  PublisherOA PDFDOI

• Restraint of TGFβ family signaling by SMAD7 is necessary for hematopoietic stem cell maturation in the embryo

  bioRxiv (Cold Spring Harbor Laboratory) · 2025-08-28

  preprintOpen accessSenior authorCorresponding

  Abstract Hematopoietic stem cells (HSCs), defined as cells that can engraft an adult when transplanted, mature from precursors (pre-HSCs) that differentiate from hemogenic endothelial cells (HECs) in the embryo. Many signaling pathways required to generate the first hematopoietic stem and progenitor cells in the embryo are well-characterized, but how HSCs mature from pre-HSCs is poorly understood. Here we show that “mothers against decapentaplegic homolog 7” (SMAD7), a negative regulator of transforming growth factor beta (TGFβ) and bone morphogenetic protein (BMP) signaling, is required for pre-HSC to HSC maturation. Deletion of Smad7 in endothelial cells allows the formation of pre-HSCs from HECs but impairs their maturation into HSCs. The data indicate that although TGFβ and BMP signaling are required for the generation of HECs and for HECs to undergo an endothelial-to-hematopoietic transition to generate pre-HSCs, one or both pathways must be subsequently down-regulated for effective pre-HSC to HSC maturation.

  PublisherOA PDFDOI

• Spatial transcriptomics identified dynamic and spatial-resolved niche cell and signal architecture for hematopoietic stem cell specification

  Blood · 2025-11-03

  articleOpen access

  Abstract Hematopoietic stem cell (HSC) transplantation remains limited by insufficient matched donors. Generating HSCs from pluripotent stem cells (PSCs) represents an attractive strategy, potentially providing unlimited autologous HSCs for therapeutic applications. However, the generated cells overall lack self-renewal capacity, indicating their inappropriate directed differentiation or immature cell state. This required deep insights into embryonic HSC specification. During embryogenesis, HSCs first arise within the dorsal aorta of the aorta-gonad-mesonephros (AGM) region, progressing through sequential stages of hemogenic endothelial cell specification and endothelial-to-hematopoietic transition. These events occur mainly on the ventral side of the dorsal aorta within a defined developmental window (mouse embryonic days (E)9.5–E12.5). Despite its importance and recent advances, the precise cellular composition and signaling landscape within this niche remain poorly defined. To address this, we combined single-cell RNA sequencing with spatial transcriptomics (Curio-seq) on trunk sections encompassing the AGM at E10.5, E11.5 and E12.5. Our analysis revealed distinct cellular distributions between the dorsal and ventral sides of the aorta. The dorsal side is enriched with Nfgr+ cells expressing BMP signaling components and a wt1+ mesonephric cell population. In contrast, the ventral aortic region exhibits complex cellular diversity and a variety of signaling pathways (including WNT, NOTCH, and retinoic acid). Notably, we identified a distinctive population of mesenchymal stromal cells co-expressing cdh2 (encode N-cadherin) and pdgfrα, forming a discrete layer between aortic endothelial cells and mesonephric cells, and directly contacting all identified pre-HSCs. Using CellChat, we identified dynamic signaling crosstalk between niche cells and pre-HSCs via ligand-receptor interactions. For example, interactions between N-cad+ MSCs and pre-HSCs, such as Dlk1-Notch1, Tgfβ1-Tgfβr1 and Jag1-Notch1, peaked at E10.5, E11.5 and E12.5, respectively. Furthermore, we mapped these interactions directly on the AGM tissue, enabling spatial-resolved visualization. Curio-seq data thus provided a 10 µm depiction of the dynamic and spatially asymmetric cellular and signaling landscape within the AGM niche. We next validated our Curio-seq findings using MERFISH, an imaging-based spatial transcriptomics approach. A customized RNA probe panel targeting 140 key genes (including cellular markers and signaling molecules) confirmed niche cell identities and signaling interactions at single-cell resolution on E11.5 AGM sections. Consistent with Curio-seq results, MERFISH verified the ventral enrichment of N-cad+ MSCs, their close physical proximity to pre-HSCs, and their role as principal sources of Dlk1, Cd200 and Sdf-1 signals around the aorta. Given the unique localization of N-cad+ MSCs and their intricate interactions with pre-HSCs, we next dissociated and reaggregated E11.5 AGM cells, with or without sorting out Cd45-Cd144- N-cad+ MSCs, to culture ex vivo and mature pre-HSCs into transplantable HSCs. Depletion of N-cad+ MSCs substantially reduced phenotypic (by flow cytometry) and functional HSCs (by transplantation assays). To define the signals from N-cad+ MSCs involved in HSC specification, we supplemented reaggregated cultures lacking N-cad+ MSCs with recombinant mouse Jag1, Cd200, or Sdf-1. Supplementation with either Jag1 or Cd200, but not Sdf-1, significantly rescued HSC specification impaired by N-cad+ MSC depletion. To directly examine the effects of N-cad+ MSC-derived Jag1 and Cd200, we generated NcadCreER; Jag1flox/flox and NcadCreER; CD200flox/flox mice and conditionally deleted Jag1 or Cd200 from N-cadherin-expressing cells at E9.5. AGM cells at E11.5 were collected for transplantation assays, and the results are pending. In summary, we utilized spatial transcriptomics to define dynamic, single-cell and spatially resolved profiles of niche cells and their emanated signals in the AGM region. We demonstrated a positive role for N-cad+ MSCs and their putatively derived Jag1 and Cd200 in HSC development. This approach validates our spatial transcriptomics results and provides a paradigm for future validation of additional signals of interest identified by spatial transcriptomics. Our findings enhance the understanding of the embryonic hematopoietic niche and provide new insights toward developing improved methods for PSC-to-HSC induction.

  PublisherOA PDFDOI

• Lineage tracing studies suggest that the placenta is not a de novo source of hematopoietic stem cells

  PLoS Biology · 2025-01-28 · 3 citations

  articleOpen accessCorresponding

  Definitive hematopoietic stem and progenitor cells (HSPCs) arise from a small number of hemogenic endothelial cells (HECs) within the developing embryo. Understanding the origin and ontogeny of HSPCs is of considerable interest and potential therapeutic value. It has been proposed that the murine placenta contains HECs that differentiate into HSPCs. However, during human gestation HSPCs arise in the aorta considerably earlier than when they can first be detected in the placenta, suggesting that the placenta may primarily serve as a niche. We found that the Runx1 transcription factor, which is required to generate HSPCs from HECs, is not expressed by mouse placental ECs. To definitively determine whether the mouse placenta is a site of HSPC emergence, we performed lineage tracing experiments with a Hoxa13Cre allele that specifically labels ECs in the placenta and umbilical cord (UC), but not in the yolk sac or embryo. Immunostaining revealed Hoxa13Cre lineage-traced HECs and HSPCs in the UC, a known site of HECs, but not the placenta. Consistent with these findings, ECs harvested from the E10.5 aorta and UC, but not the placenta, gave rise to hematopoietic cells ex vivo, while colony forming assays using E14.5 fetal liver revealed only 2% of HSPCs arose from Hoxa13-expressing precursors. In contrast, the pan-EC Cdh5-CreERT2 allele labeled most HSPCs in the mouse placenta. Lastly, we found that RUNX1 and other HEC genes were not expressed in first-trimester human placenta villous ECs, suggesting that human placenta is not hemogenic. Our findings demonstrate that the placenta functions as a site for expansion of HSPCs that arise within the embryo proper and is not a primary site of HSPC emergence.

  PublisherDOI

• Human length telomeres restrict the regenerative potential of hematopoietic stem cells in mice

  bioRxiv (Cold Spring Harbor Laboratory) · 2025-08-30

  preprintOpen access

  Abstract Extremely short telomeres cause bone marrow failure in telomere biology disorder (TBDs) patients. Here, we employed the recently developed ‘Telomouse’ with human-length telomeres resulting from a single amino acid substitution in the helicase Rtel1 ( Rtel1 M492K/M492K ) to determine the effects of the short telomeres on the bone marrow and hematopoiesis. Under homeostatic conditions, Telomice have notably short telomeres but normal hematopoiesis. However, when forced to repopulate following repeated treatment with 5-fluoro-uracil or upon bone marrow transplantation into lethally irradiated mice, bone marrow progenitor cells are significantly depleted in Telomice compared to wild-type controls. This effect is associated with increased frequency of telomere repeat arrays too short to be detected by fluorescence in situ hybridization in the bone marrow of Telomice.

  PublisherOA PDFDOI

• E2f coordinates the cell cycle and cell fate of hematopoietic progenitors to drive stress myelopoiesis

  bioRxiv (Cold Spring Harbor Laboratory) · 2025-06-18

  preprint

  ABSTRACT During inflammation, cytokines such as Tnfα, Il1β and Il6 stimulate hematopoietic stem and progenitor cells (HSPCs) to proliferate and accelerate the production of inflammatory cells from the myeloid lineage through a process called stress myelopoiesis. Genetic inactivation of repressors of cell cycle activity in HSPCs is sufficient to recapitulate stress myelopoiesis, suggesting that the cell cycle activity and cell fate decision of proliferative HSPCs are coordinated by a cell intrinsic mechanism. However, the nature of this mechanism remains unknown. Here, we show that E2f simultaneously regulates proliferation of HSPCs, repression of alternative cell fates via the activation of Suz12 / Ezh2 -containing PRC2 complex and promotion of the myeloid fate by enhancing the signaling activity of CD131, the common βchain receptor for βcytokines (i.e. Il3 and Gm-Csf). Accordingly, dual inhibition of Ezh2 and βcytokine signaling activity in a preclinical model of colitis represses stress myelopoiesis and restores colon homeostasis. Our results suggest that dual targeting of βcytokine signaling and Ezh2 activity represents a novel therapeutic strategy to repress the production of pro-inflammatory myeloid cells in a wide spectrum of inflammatory diseases.

  PublisherDOI

• Restraint of TGF-β signaling by SMAD7 is necessary for the maturation of hematopoietic stem cells in the mouse embryo

  Blood · 2025-11-03

  articleSenior author

  Abstract Hematopoietic stem and progenitor cells (HSPCs) in the mouse embryo arise from a subset of arterial hemogenic endothelial cells which bud into the lumen of the major vessels, forming intra-arterial hematopoietic cluster (IAHC) cells – a heterogenous population of non-HSC derived progenitors, the precursors of HSCs (pre-HSCs), and HSCs (Kissa and Herbomel 2010, Zhu, Gao et al. 2020). The first HSCs arise at embryonic day (E) 11.5 in the mouse embryo– almost 4 days after the onset of hematopoiesis and after hundreds of committed progenitors have already emerged (de Bruijn, Speck et al. 2000, Rybtsov, Sobiesiak et al. 2011, Gordon-Keylock, Sobiesiak et al. 2013, Rybtsov, Ivanovs et al. 2016). At E11.5, there are an estimated 65 pre-HSCs and 1 functional HSC (Rybtsov, Ivanovs et al. 2016). The rarity of these cells poses a significant challenge for identifying signals or genes required for their formation. We previously performed single-cell transcriptional profiling of endothelial cells, hemogenic endothelial cells, and HSPCs during hematopoietic development and found that a negative regulator of TGF-β signaling, Smad7, was specifically upregulated in pre-HSCs, suggesting that inhibition of TGF-β signaling may be necessary to generate pre-HSCs or HSCs. TGF-β signaling plays an essential role early in the specification of hemogenic endothelial cells, but how the restraint of TGF-β signaling affects the generation of pre-HSCs or their maturation into HSCs later in hematopoietic development is unknown. Deleting Smad7 at E9.5 using an endothelial-specific Cre (Smad7 KO) does not impact the number of IAHC cells or non-HSC-derived progenitors but results in a complete loss of functional adult-repopulating HSCs in the aorta-gonad-mesonephros region (AGM) in E11.5 Smad7 KOembryos. Limiting dilution transplants of E12.5 AGMs, which normally contain approximately 2-3 HSCs, revealed an 85% reduction in HSCs in Smad7 KOembryos compared to wild type embryos (0.52 HSCs/AGM Smad7 KO vs 2.56 HSCs/AGM WT, p=5.3e-6). HSPCs eventually migrate from the AGM to the fetal liver (FL). We observed a 60% reduction in HSCs in the E12.5 FL (11.0 HSCs/FL Smad7 KO vs 26.2 HSCs/FL WT, p=0.0167), suggesting that the reduction in HSCs in the AGM of Smad7 KO embryos is not the result of precocious migration of HSCs to the FL. Pre-HSCs are defined functionally as cells that cannot directly engraft an irradiated adult but can be matured ex vivo into adult repopulating cells. We performed a limiting dilution pre-HSC maturation assay by sorting IAHC cells from E11.5 embryos and found Smad7 KO IAHC cells had an 85% reduction in functional pre-HSCs (1:181 WT vs 1:1084 Smad7 KO, p=2.59e-5). We performed scRNA-seq profiling of wild type and Smad7 KO endothelial and IAHC cells at E11.5 to determine whether the generation of pre-HSCs was affected by loss of SMAD7. scRNA-seq revealed that the loss of SMAD7 increased the proportion of pre-HSCs relative to other hematopoietic cells by approximately 2-fold (p=0.003), indicating that pre-HSC formation was not affected and suggesting instead that pre-HSC to HSC maturation may be impaired. We directly examined the role of SMAD7 in pre-HSC maturation by deleting Smad7 with a ubiquitously expressed Rosa26CreERT after cells were sorted from E11.5 embryos. Ex vivo deletion of SMAD7 in pre-HSCs resulted in an 87% decrease in functional LT-HSCs (1:252 WT vs 1:1075 Smad7 KO, p=0.004), indicating that inhibiting TGF-β signaling is necessary for the proper maturation of pre-HSCs into HSCs but not their formation from endothelial cells. In summary, we identified the first signaling pathway in hematopoietic development that specifically promotes the maturation of HSCs from their embryonic precursors (pre-HSCs). Several groups have successfully demonstrated the ability to produce HSCs from iPSC cultures (Piau, Brunet-Manquat et al. 2023, Ng, Sarila et al. 2024). Understanding the signals required in the specification and maturation of HSCs in vivo during development, and when they should be applied and inhibited, will inform efforts to optimize HSC production from iPSCs.

  PublisherDOI

• Alternating high-fat diet enhances atherosclerosis by neutrophil reprogramming

  Nature · 2024-09-04 · 89 citations

  articleOpen access
  PublisherOA PDFDOI

• 3024 – RESTRAINT OF TGF-B SIGNALING BY SMAD7 IS NECESSARY FOR HEMATOPOIETIC STEM CELL FORMATION IN THE MOUSE EMBRYO

  Experimental Hematology · 2024-08-01

  articleSenior author
  PublisherDOI

• Tropomyosin 1 deficiency facilitates cell state transitions and enhances hemogenic endothelial cell specification during hematopoiesis

  Stem Cell Reports · 2024-08-29 · 6 citations

  articleOpen access

  Tropomyosins coat actin filaments to impact actin-related signaling and cell morphogenesis. Genome-wide association studies have linked Tropomyosin 1 (TPM1) with human blood trait variation. TPM1 has been shown to regulate blood cell formation in vitro, but it remains unclear how or when TPM1 affects hematopoiesis. Using gene-edited induced pluripotent stem cell (iPSC) model systems, we found that TPM1 knockout augmented developmental cell state transitions and key signaling pathways, including tumor necrosis factor alpha (TNF-α) signaling, to promote hemogenic endothelial (HE) cell specification and hematopoietic progenitor cell (HPC) production. Single-cell analyses revealed decreased TPM1 expression during human HE specification, suggesting that TPM1 regulated in vivo hematopoiesis via similar mechanisms. Analyses of a TPM1 gene trap mouse model showed that TPM1 deficiency enhanced HE formation during embryogenesis, without increasing the number of hematopoietic stem cells. These findings illuminate novel effects of TPM1 on developmental hematopoiesis.

  PublisherDOI

Recent grants

• Mechanisms of endothelial-to-hemogenic transition mediated by Runx1

  NIH · $2.1M · 2017–2023

• NIH Grant R01CA075611

  NIH · $2.1M · 2008

• NIH Grant R01CA149976

  NIH · $1.9M · 2016

• NIH Grant T32GM008704

  NIH · $7.0M · 2019

• NIH Grant R21HD081054

  NIH · $441k · 2018

Frequent coauthors

• Kai Tan

  Children's Hospital of Philadelphia

  68 shared

• Joanna Tober

  University of Pennsylvania

  67 shared

• Amanda D. Yzaguirre

  Fate Therapeutics (United States)

  64 shared

• Xiongwei Cai

  55 shared

• D. Gary Gilliland

  52 shared

• Terryl Stacy

  Office of Research Services

  49 shared

• Peiqing Liu

  Sun Yat-sen University

  47 shared

• Koichi Akashi

  Kyushu University

  41 shared

Labs

• Speck LabPI