RESUMEN
BACKGROUND: Liver function tests (LFTs) are elevated in >50% of hospitalized individuals infected with severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2), with increased enzyme levels correlating with a more severe COVID-19 course. Despite these observations, evaluations of viral presence within liver parenchyma and viral impact on liver function remain controversial. METHODS AND RESULTS: Our work is a comprehensive immunopathological evaluation of liver tissue from 33 patients with severe, and ultimately fatal, cases of SARS-CoV-2 infection. Coupled with clinical data, we reveal the absence of SARS-CoV-2 infection in cholangiocytes and hepatocytes despite dramatic systemic viral presence. Critically, we identify significant focal viral sinusoidal aggregates in 2/33 patients and single viral RNA molecules circulating in the hepatic sinusoids of 15/33 patients. Utilizing co-immunofluorescence, focal viral liver aggregates in patients with COVID-19 were colocalized to platelet and fibrin clots, indicating the presence of virus-containing sinusoidal microthrombi. Furthermore, this patient cohort, from the initial months of the COVID-19 pandemic, demonstrates a general downtrend of LFTs over the course of the study timeline and serves as a remarkable historical time point of unattenuated viral replication within patients. CONCLUSIONS: Together, our findings indicate that elevated LFTs found in our patient cohort are not due to direct viral parenchymal infection with SARS-CoV-2 but rather likely a consequence of systemic complications of COVID-19. This work aids in the clinical treatment considerations of patients with SARS-CoV-2 as therapies for these patients may be considered in terms of their direct drug hepatotoxity rather than worsening hepatic function due to direct infection.
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COVID-19 , Hepatopatías , Humanos , SARS-CoV-2 , COVID-19/complicaciones , PandemiasRESUMEN
Polycomb repressive complex 2 (PRC2) silences genes through trimethylation of histone H3K27. PRC2 associates with numerous precursor messenger RNAs (pre-mRNAs) and long noncoding RNAs (lncRNAs) with a binding preference for G-quadruplex RNA. In this work, we present a 3.3-Å-resolution cryo-electron microscopy structure of PRC2 bound to a G-quadruplex RNA. Notably, RNA mediates the dimerization of PRC2 by binding both protomers and inducing a protein interface composed of two copies of the catalytic subunit EZH2, thereby blocking nucleosome DNA interaction and histone H3 tail accessibility. Furthermore, an RNA-binding loop of EZH2 facilitates the handoff between RNA and DNA, another activity implicated in PRC2 regulation by RNA. We identified a gain-of-function mutation in this loop that activates PRC2 in zebrafish. Our results reveal mechanisms for RNA-mediated regulation of a chromatin-modifying enzyme.
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G-Cuádruplex , Complejo Represivo Polycomb 2 , Precursores del ARN , ARN Largo no Codificante , Animales , Microscopía por Crioelectrón , Histonas/genética , Complejo Represivo Polycomb 2/química , Complejo Represivo Polycomb 2/genética , ARN Largo no Codificante/química , ARN Largo no Codificante/genética , Pez Cebra/genética , Pez Cebra/crecimiento & desarrollo , Mutación con Ganancia de Función , Regiones Promotoras Genéticas , Unión Proteica , Proteína Potenciadora del Homólogo Zeste 2/química , Proteína Potenciadora del Homólogo Zeste 2/genética , Cristalografía por Rayos X , Conformación Proteica , Multimerización de ProteínaRESUMEN
Ethanol (EtOH) is a commonly encountered teratogen that can disrupt organ development and lead to fetal alcohol spectrum disorders (FASDs); many mechanisms of developmental toxicity are unknown. Here, we used transcriptomic analysis in an established zebrafish model of embryonic alcohol exposure (EAE) to identify the ubiquitin-proteasome system (UPS) as a critical target of EtOH during development. Surprisingly, EAE alters 20S, 19S, and 11S proteasome gene expression and increases ubiquitylated protein load. EtOH and its metabolite acetaldehyde decrease proteasomal peptidase activity in a cell type-specific manner. Proteasome 20S subunit ß 1 (psmb1hi2939Tg) and proteasome 26S subunit, ATPase 6 (psmc6hi3593Tg), genetic KOs define the developmental impact of decreased proteasome function. Importantly, loss of psmb1 or psmc6 results in widespread developmental abnormalities resembling EAE phenotypes, including growth restriction, abnormal craniofacial structure, neurodevelopmental defects, and failed hepatopancreas maturation. Furthermore, pharmacologic inhibition of chymotrypsin-like proteasome activity potentiates the teratogenic effects of EAE on craniofacial structure, the nervous system, and the endoderm. Our studies identify the proteasome as a target of EtOH exposure and signify that UPS disruptions contribute to craniofacial, neurological, and endodermal phenotypes in FASDs.
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Complejo de la Endopetidasa Proteasomal , Ubiquitina , Animales , Pez Cebra , Etanol/toxicidadRESUMEN
Human induced pluripotent stem cells (iPSCs) provide a potentially unlimited resource for cell therapies, but the derivation of mature cell types remains challenging. The histone methyltransferase EZH1 is a negative regulator of lymphoid potential during embryonic hematopoiesis. Here, we demonstrate that EZH1 repression facilitates in vitro differentiation and maturation of T cells from iPSCs. Coupling a stroma-free T cell differentiation system with EZH1-knockdown-mediated epigenetic reprogramming, we generated iPSC-derived T cells, termed EZ-T cells, which display a highly diverse T cell receptor (TCR) repertoire and mature molecular signatures similar to those of TCRαß T cells from peripheral blood. Upon activation, EZ-T cells give rise to effector and memory T cell subsets. When transduced with chimeric antigen receptors (CARs), EZ-T cells exhibit potent antitumor activities in vitro and in xenograft models. Epigenetic remodeling via EZH1 repression allows efficient production of developmentally mature T cells from iPSCs for applications in adoptive cell therapy.
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Células Madre Pluripotentes Inducidas , Receptores Quiméricos de Antígenos , Diferenciación Celular , Humanos , Inmunoterapia Adoptiva , Células Madre Pluripotentes Inducidas/metabolismo , Complejo Represivo Polycomb 2/metabolismo , Receptores Quiméricos de Antígenos/metabolismo , Linfocitos TRESUMEN
Hematopoiesis changes over life to meet the demands of maturation and aging. Here, we find that the definitive hematopoietic stem and progenitor cell (HSPC) compartment is remodeled from gestation into adulthood, a process regulated by the heterochronic Lin28b/let-7 axis. Native fetal and neonatal HSPCs distribute with a pro-lymphoid/erythroid bias with a shift toward myeloid output in adulthood. By mining transcriptomic data comparing juvenile and adult HSPCs and reconstructing coordinately activated gene regulatory networks, we uncover the Polycomb repressor complex 1 (PRC1) component Cbx2 as an effector of Lin28b/let-7's control of hematopoietic maturation. We find that juvenile Cbx2-/- hematopoietic tissues show impairment of B-lymphopoiesis, a precocious adult-like myeloid bias, and that Cbx2/PRC1 regulates developmental timing of expression of key hematopoietic transcription factors. These findings define a mechanism of regulation of HSPC output via chromatin modification as a function of age with potential impact on age-biased pediatric and adult blood disorders.
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Hematopoyesis , Células Madre Hematopoyéticas , MicroARNs , Complejo Represivo Polycomb 1 , Proteínas de Unión al ARN , Adulto , Animales , Niño , Redes Reguladoras de Genes , Hematopoyesis/genética , Células Madre Hematopoyéticas/metabolismo , Humanos , Recién Nacido , Linfopoyesis , Ratones , Complejo Represivo Polycomb 1/genética , Complejo Represivo Polycomb 1/metabolismo , Proteínas del Grupo Polycomb/metabolismo , Proteínas de Unión al ARN/genética , Proteínas de Unión al ARN/metabolismoRESUMEN
High-risk forms of B-acute lymphoblastic leukemia (B-ALL) remain a therapeutic challenge. Leukemia-initiating cells (LICs) self-renew and spark relapse and therefore have been the subject of intensive investigation; however, the properties of LICs in high-risk B-ALL are not well understood. Here, we use single-cell transcriptomics and quantitative xenotransplantation to understand LICs in MLL-rearranged (MLL-r) B-ALL. Compared with reported LIC frequencies in acute myeloid leukemia (AML), engraftable LICs in MLL-r B-ALL are abundant. Although we find that multipotent, self-renewing LICs are enriched among phenotypically undifferentiated B-ALL cells, LICs with the capacity to replenish the leukemic cellular diversity can emerge from more mature fractions. While inhibiting oxidative phosphorylation blunts blast proliferation, this intervention promotes LIC emergence. Conversely, inhibiting hypoxia and glycolysis impairs MLL-r B-ALL LICs, providing a therapeutic benefit in xenotransplantation systems. These findings provide insight into the aggressive nature of MLL-r B-ALL and provide a rationale for therapeutic targeting of hypoxia and glycolysis.
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Leucemia Mieloide Aguda , Leucemia-Linfoma Linfoblástico de Células Precursoras , Glucólisis , Humanos , Hipoxia , Leucemia Mieloide Aguda/metabolismo , Leucemia-Linfoma Linfoblástico de Células Precursoras/genéticaRESUMEN
Intercellular communication orchestrates a multitude of physiologic and pathologic conditions. Algorithms to infer cell-cell communication and predict downstream signalling and regulatory networks are needed to illuminate mechanisms of stem cell differentiation and tissue development. Here, to fill this gap, we developed and applied CellComm to investigate how the aorta-gonad-mesonephros microenvironment dictates haematopoietic stem and progenitor cell emergence. We identified key microenvironmental signals and transcriptional networks that regulate haematopoietic development, including Stat3, Nr0b2, Ybx1 and App, and confirmed their roles using zebrafish, mouse and human models. Notably, CellComm revealed extensive crosstalk among signalling pathways and convergence on common transcriptional regulators, indicating a resilient developmental programme that ensures dynamic adaptation to changes in the embryonic environment. Our work provides an algorithm and data resource for the scientific community.
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Células Madre Hematopoyéticas , Pez Cebra , Animales , Diferenciación Celular , Hematopoyesis/fisiología , Células Madre Hematopoyéticas/metabolismo , Mesonefro/metabolismo , Ratones , Pez Cebra/genéticaRESUMEN
It is increasingly recognized that specialized subsets of endothelial cells carry out unique functions in specific organs and regions of the vascular tree. Perhaps the most striking example of this specialization is the ability to contribute to the generation of the blood system, in which a distinct population of "hemogenic" endothelial cells in the embryo transforms irreversibly into hematopoietic stem and progenitor cells that produce circulating erythroid, myeloid and lymphoid cells for the lifetime of an animal. This review will focus on recent advances made in the zebrafish model organism uncovering the extrinsic and environmental factors that facilitate hemogenic commitment and the process of endothelial-to-hematopoietic transition that produces blood stem cells. We highlight in particular biomechanical influences of hemodynamic forces and the extracellular matrix, metabolic and sterile inflammatory cues present during this developmental stage, and outline new avenues opened by transcriptomic-based approaches to decipher cell-cell communication mechanisms as examples of key signals in the embryonic niche that regulate hematopoiesis.
RESUMEN
The molecular mechanisms that govern the choreographed timing of organ development remain poorly understood. Our investigation of the role of the Lin28a and Lin28b paralogs during the developmental process of branching morphogenesis establishes that dysregulation of Lin28a/b leads to abnormal branching morphogenesis in the lung and other tissues. Additionally, we find that the Lin28 paralogs, which regulate post-transcriptional processing of both mRNAs and microRNAs (miRNAs), predominantly control mRNAs during the initial phases of lung organogenesis. Target mRNAs include Sox2, Sox9, and Etv5, which coordinate lung development and differentiation. Moreover, we find that functional interactions between Lin28a and Sox9 are capable of bypassing branching defects in Lin28a/b mutant lungs. Here, we identify Lin28a and Lin28b as regulators of early embryonic lung development, highlighting the importance of the timing of post-transcriptional regulation of both miRNAs and mRNAs at distinct stages of organogenesis.
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Pulmón/embriología , Pulmón/metabolismo , Morfogénesis , Proteínas de Unión al ARN/metabolismo , Homología de Secuencia de Aminoácido , Embrión de Mamíferos/metabolismo , Retroalimentación Fisiológica , Factor 10 de Crecimiento de Fibroblastos/metabolismo , Regulación del Desarrollo de la Expresión Génica , Células HEK293 , Proteínas Hedgehog/metabolismo , Humanos , MicroARNs/genética , MicroARNs/metabolismo , Modelos Biológicos , Morfogénesis/genética , Proteínas de Unión al ARN/genética , Factor de Transcripción SOX9/metabolismo , Transducción de Señal/genéticaRESUMEN
Across species, hematopoietic stem and progenitor cells (HSPCs) arise during embryogenesis from a specialized arterial population, termed hemogenic endothelium. Here, we describe a mechanistic role for the epigenetic regulator, Enhancer of zeste homolog-1 (Ezh1), in vertebrate HSPC production via regulation of hemogenic commitment. Loss of ezh1 in zebrafish embryos favored acquisition of hemogenic (gata2b) and HSPC (runx1) fate at the expense of the arterial program (ephrinb2a, dll4). In contrast, ezh1 overexpression blocked hematopoietic progression via maintenance of arterial gene expression. The related Polycomb group subunit, Ezh2, functioned in a non-redundant, sequential manner, whereby inhibition had no impact on arterial identity, but was capable of blocking ezh1-knockdown-associated HSPC expansion. Single-cell RNA sequencing across ezh1 genotypes revealed a dropout of ezh1+/- cells among arterial endothelium associated with positive regulation of gene transcription. Exploitation of Ezh1/2 modulation has potential functional relevance for improving in vitro HSPC differentiation from induced pluripotent stem cell sources.
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Proteína Potenciadora del Homólogo Zeste 2/metabolismo , Hemangioblastos/metabolismo , Células Madre Hematopoyéticas/metabolismo , Complejo Represivo Polycomb 2/metabolismo , Proteínas de Pez Cebra/metabolismo , Pez Cebra/metabolismo , Animales , Embrión no Mamífero/metabolismo , Células Endoteliales/metabolismo , Técnicas de Silenciamiento del Gen , Hematopoyesis , Mutación con Pérdida de Función , Linfocitos/metabolismo , Ratones , RNA-Seq , Análisis de la Célula IndividualRESUMEN
In this issue of Developmental Cell, Weinreb et al. reveal that loss of the DEAD-box helicase Ddx41 unexpectedly triggers an R-loop-mediated sterile inflammatory cascade which drives HSPC production during embryonic development. Human studies suggest mechanistic conservation for inflammation in DDX41-associated hematologic disease, uncovering a potential route for future therapeutic intervention.
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ARN Helicasas DEAD-box , Estructuras R-Loop , ARN Helicasas DEAD-box/genética , ARN Helicasas DEAD-box/metabolismo , ADN Helicasas , Humanos , NucleotidiltransferasasRESUMEN
Fanconi anemia (FA) is a disorder of DNA repair that manifests as bone marrow (BM) failure. The lack of accurate murine models of FA has refocused efforts toward differentiation of patient-derived induced pluripotent stem cells (IPSCs) to hematopoietic progenitor cells (HPCs). However, an intact FA DNA repair pathway is required for efficient IPSC derivation, hindering these efforts. To overcome this barrier, we used inducible complementation of FANCA-deficient IPSCs, which permitted robust maintenance of IPSCs. Modulation of FANCA during directed differentiation to HPCs enabled the production of FANCA-deficient human HPCs that recapitulated FA genotoxicity and hematopoietic phenotypes relative to isogenic FANCA-expressing HPCs. FANCA-deficient human HPCs underwent accelerated terminal differentiation driven by activation of p53/p21. We identified growth arrest specific 6 (GAS6) as a novel target of activated p53 in FANCA-deficient HPCs and modulate GAS6 signaling to rescue hematopoiesis in FANCA-deficient cells. This study validates our strategy to derive a sustainable, highly faithful human model of FA, uncovers a mechanism of HPC exhaustion in FA, and advances toward future cell therapy in FA.
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Anemia de Fanconi , Células Madre Pluripotentes Inducidas , Animales , Diferenciación Celular , Anemia de Fanconi/genética , Proteína del Grupo de Complementación A de la Anemia de Fanconi/genética , Humanos , Ratones , Proteína p53 Supresora de Tumor/genéticaRESUMEN
Embryonic hematopoietic stem and progenitor cells (HSPCs) robustly proliferate while maintaining multilineage potential in vivo; however, an incomplete understanding of spatiotemporal cues governing their generation has impeded robust production from human induced pluripotent stem cells (iPSCs) in vitro. Using the zebrafish model, we demonstrate that NLRP3 inflammasome-mediated interleukin-1-beta (IL1ß) signaling drives HSPC production in response to metabolic activity. Genetic induction of active IL1ß or pharmacologic inflammasome stimulation increased HSPC number as assessed by in situ hybridization for runx1/cmyb and flow cytometry. Loss of inflammasome components, including il1b, reduced CD41+ HSPCs and prevented their expansion in response to metabolic cues. Cell ablation studies indicated that macrophages were essential for initial inflammasome stimulation of Il1rl1+ HSPCs. Significantly, in human iPSC-derived hemogenic precursors, transient inflammasome stimulation increased multilineage hematopoietic colony-forming units and T cell progenitors. This work establishes the inflammasome as a conserved metabolic sensor that expands HSPC production in vivo and in vitro.
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Células Madre Embrionarias/metabolismo , Células Madre Hematopoyéticas/metabolismo , Células Madre Pluripotentes Inducidas/metabolismo , Inflamasomas/metabolismo , Animales , Diferenciación Celular/fisiología , Subunidad alfa 2 del Factor de Unión al Sitio Principal/metabolismo , Embrión no Mamífero/metabolismo , Desarrollo Embrionario/fisiología , Hematopoyesis/fisiología , Humanos , Pez Cebra/embriologíaRESUMEN
Studies of hematopoietic stem cell (HSC) development from pre-HSC-producing hemogenic endothelial cells (HECs) are hampered by the rarity of these cells and the presence of other cell types with overlapping marker expression profiles. We generated a Tg(Runx1-mKO2; Ly6a-GFP) dual reporter mouse to visualize hematopoietic commitment and study pre-HSC emergence and maturation. Runx1-mKO2 marked all intra-arterial HECs and hematopoietic cluster cells (HCCs), including pre-HSCs, myeloid- and lymphoid progenitors, and HSCs themselves. However, HSC and lymphoid potential were almost exclusively found in reporter double-positive (DP) cells. Robust HSC activity was first detected in DP cells of the placenta, reflecting the importance of this niche for (pre-)HSC maturation and expansion before the fetal liver stage. A time course analysis by single-cell RNA sequencing revealed that as pre-HSCs mature into fetal liver stage HSCs, they show signs of interferon exposure, exhibit signatures of multi-lineage differentiation gene expression, and develop a prolonged cell cycle reminiscent of quiescent adult HSCs.
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Antígenos Ly/genética , Subunidad alfa 2 del Factor de Unión al Sitio Principal/genética , Genes Reporteros , Hematopoyesis , Células Madre Hematopoyéticas/metabolismo , Proteínas de la Membrana/genética , Transcriptoma , Animales , Antígenos Ly/metabolismo , Células Cultivadas , Células Progenitoras Endoteliales/citología , Células Progenitoras Endoteliales/metabolismo , Proteínas Fluorescentes Verdes/genética , Proteínas Fluorescentes Verdes/metabolismo , Células Madre Hematopoyéticas/citología , Proteínas de la Membrana/metabolismo , Ratones , RNA-Seq , Proteínas Recombinantes/genética , Proteínas Recombinantes/metabolismo , Análisis de la Célula IndividualRESUMEN
Hematopoietic stem and progenitor cells (HSPCs), first specified from hemogenic endothelium (HE) in the ventral dorsal aorta (VDA), support lifelong hematopoiesis. Their de novo production promises significant therapeutic value; however, current in vitro approaches cannot efficiently generate multipotent long-lived HSPCs. Presuming this reflects a lack of extrinsic cues normally impacting the VDA, we devised a human dorsal aorta-on-a-chip platform that identified Yes-activated protein (YAP) as a cyclic stretch-induced regulator of HSPC formation. In the zebrafish VDA, inducible Yap overexpression significantly increased runx1 expression in vivo and the number of CD41+ HSPCs downstream of HE specification. Endogenous Yap activation by lats1/2 knockdown or Rho-GTPase stimulation mimicked Yap overexpression and induced HSPCs in embryos lacking blood flow. Notably, in static human induced pluripotent stem cell (iPSC)-derived HE culture, compound-mediated YAP activation enhanced RUNX1 levels and hematopoietic colony-forming potential. Together, our findings reveal a potent impact of hemodynamic Rho-YAP mechanotransduction on HE fate, relevant to de novo human HSPC production.
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Proteínas de Ciclo Celular/metabolismo , Subunidad alfa 2 del Factor de Unión al Sitio Principal/metabolismo , Endotelio Vascular/citología , Hematopoyesis , Células Madre Hematopoyéticas/citología , Células Madre Pluripotentes Inducidas/citología , Mecanotransducción Celular , Factores de Transcripción/metabolismo , Animales , Aorta/citología , Aorta/embriología , Proteínas de Ciclo Celular/genética , Diferenciación Celular , Subunidad alfa 2 del Factor de Unión al Sitio Principal/genética , Embrión no Mamífero/citología , Embrión no Mamífero/metabolismo , Endotelio Vascular/metabolismo , Células Madre Hematopoyéticas/fisiología , Hemodinámica , Humanos , Células Madre Pluripotentes Inducidas/fisiología , Factores de Transcripción/genética , Pez Cebra , Proteínas de Unión al GTP rho/metabolismoRESUMEN
BACKGROUND AND AIMS: During liver development, bipotent progenitor cells differentiate into hepatocytes and biliary epithelial cells to ensure a functional liver required to maintain organismal homeostasis. The developmental cues controlling the differentiation of committed progenitors into these cell types, however, are incompletely understood. Here, we discover an essential role for estrogenic regulation in vertebrate liver development to affect hepatobiliary fate decisions. APPROACH AND RESULTS: Exposure of zebrafish embryos to 17ß-estradiol (E2) during liver development significantly decreased hepatocyte-specific gene expression, liver size, and hepatocyte number. In contrast, pharmacological blockade of estrogen synthesis or nuclear estrogen receptor (ESR) signaling enhanced liver size and hepatocyte marker expression. Transgenic reporter fish demonstrated nuclear ESR activity in the developing liver. Chemical inhibition and morpholino knockdown of nuclear estrogen receptor 2b (esr2b) increased hepatocyte gene expression and blocked the effects of E2 exposure. esr2b-/- mutant zebrafish exhibited significantly increased expression of hepatocyte markers with no impact on liver progenitors, other endodermal lineages, or vasculature. Significantly, E2-stimulated Esr2b activity promoted biliary epithelial differentiation at the expense of hepatocyte fate, whereas loss of esr2b impaired biliary lineage commitment. Chemical and genetic epistasis studies identified bone morphogenetic protein (BMP) signaling as a mediator of the estrogen effects. The divergent impact of estrogen on hepatobiliary fate was confirmed in a human hepatoblast cell line, indicating the relevance of this pathway for human liver development. CONCLUSIONS: Our studies identify E2, esr2b, and downstream BMP activity as important regulators of hepatobiliary fate decisions during vertebrate liver development. These results have significant clinical implications for liver development in infants exposed to abnormal estrogen levels or estrogenic compounds during pregnancy.
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Sistema Biliar/embriología , Estradiol/metabolismo , Receptor beta de Estrógeno/metabolismo , Regulación del Desarrollo de la Expresión Génica , Hígado/embriología , Proteínas de Pez Cebra/metabolismo , Animales , Animales Modificados Genéticamente , Sistema Biliar/citología , Sistema Biliar/metabolismo , Diferenciación Celular/genética , Línea Celular , Embrión no Mamífero , Estradiol/administración & dosificación , Receptor beta de Estrógeno/genética , Femenino , Técnicas de Silenciamiento del Gen , Hepatocitos/fisiología , Hígado/citología , Hígado/metabolismo , Masculino , Modelos Animales , Morfolinos/administración & dosificación , Morfolinos/genética , Transducción de Señal/genética , Células Madre/fisiología , Pez Cebra , Proteínas de Pez Cebra/genéticaRESUMEN
In the version of this article initially published, the second NIH grant "R24-DK49216" to author George Q. Daley contained an error. The grant number should have read U54DK110805. The error has been corrected in the HTML and PDF versions of the article.
RESUMEN
A major challenge for stem cell engineering is achieving a holistic understanding of the molecular networks and biological processes governing cell differentiation. To address this challenge, we describe a computational approach that combines gene expression analysis, previous knowledge from proteomic pathway informatics and cell signaling models to delineate key transitional states of differentiating cells at high resolution. Our network models connect sparse gene signatures with corresponding, yet disparate, biological processes to uncover molecular mechanisms governing cell fate transitions. This approach builds on our earlier CellNet and recent trajectory-defining algorithms, as illustrated by our analysis of hematopoietic specification along the erythroid lineage, which reveals a role for the EGF receptor family member, ErbB4, as an important mediator of blood development. We experimentally validate this prediction and perturb the pathway to improve erythroid maturation from human pluripotent stem cells. These results exploit an integrative systems perspective to identify new regulatory processes and nodes useful in cell engineering.
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Ingeniería Celular , Células Madre Hematopoyéticas/metabolismo , Células Madre Pluripotentes Inducidas/fisiología , Biología de Sistemas/métodos , Algoritmos , Animales , Antígenos CD34/genética , Antígenos CD34/metabolismo , Diferenciación Celular , Linaje de la Célula , Proliferación Celular , Biología Computacional/métodos , Eritrocitos , Eritropoyesis , Citometría de Flujo , Regulación de la Expresión Génica , Redes Reguladoras de Genes , Humanos , Ratones , Receptor ErbB-4/metabolismo , Transducción de Señal , Pez CebraRESUMEN
Leukemia phenotypes vary with age of onset. Delineating mechanisms of age specificity in leukemia could improve disease models and uncover new therapeutic approaches. Here, we used heterochronic transplantation of leukemia driven by MLL/KMT2A translocations to investigate the contribution of the age of the hematopoietic microenvironment to age-specific leukemia phenotypes. When driven by MLL-AF9, leukemia cells in the adult microenvironment sustained a myeloid phenotype, whereas the neonatal microenvironment supported genesis of mixed early B cell/myeloid leukemia. In MLL-ENL leukemia, the neonatal microenvironment potentiated B-lymphoid differentiation compared with the adult. Ccl5 elaborated from adult marrow stroma inhibited B-lymphoid differentiation of leukemia cells, illuminating a mechanism of age-specific lineage commitment. Our study illustrates the contribution of the developmental stage of the hematopoietic microenvironment in defining the age specificity of leukemia.