ABSTRACT
To understand the complex interactions between hematopoietic stem cells and the bone marrow niche, a human experimental model is needed. Our hypothesis is that hematons are an appropriate ex vivo model of human bone marrow. We analyzed the hierarchical hematopoietic cell content and the tissue organization of single hematons from healthy donors. Most (>90%) hematons contained precursors of all cell lineages, myeloid progenitors, and LTC-ICs without preferential commitment. Approximately, half of the hematons could generate significant levels of lympho-myeloid hematopoiesis after transplantation in an NSG mouse model, despite the low absolute numbers of transplanted CD34+ cells. Mesenchymal STRO-1+ and/or CD271+ cells formed a critical network that preserved hematon cohesion, and STRO-1+ cells colocalized with most hematopoietic CD34+ cells (68%). We observed an influence of age and gender. These structures represent a particularly attractive model for studying the homeostasis of the bone marrow niche and pathological changes that occur during diseases.
Subject(s)
Bone Marrow Cells/cytology , Hematopoiesis/physiology , Hematopoietic Stem Cells/cytology , Models, Biological , Adolescent , Adult , Aged , Aged, 80 and over , Animals , Bone Marrow/physiology , Bone Marrow/ultrastructure , Bone Marrow Cells/physiology , Bone Marrow Cells/ultrastructure , Cell Communication/physiology , Female , Flow Cytometry , Healthy Volunteers , Hematopoietic Stem Cell Transplantation , Hematopoietic Stem Cells/physiology , Hematopoietic Stem Cells/ultrastructure , Humans , Male , Mice , Microscopy, Confocal , Microscopy, Electron , Middle Aged , Transplantation, Heterologous , Young AdultABSTRACT
BACKGROUND: Expansion of hematopoietic stem cells represents an important objective for improving cell and gene therapy protocols. Retroviral transduction of the HoxB4 homeogene in mouse and human hematopoietic stem cells and hematopoietic progenitors is known to promote the cells' expansion. A safer approach consists in transferring homeobox proteins into hematopoietic stem cells taking advantage of the natural ability of homeoproteins to cross cell membranes. Thus, HOXB4 protein transfer is operative for expanding human hematopoietic cells, but such expansion needs to be improved. DESIGN AND METHODS: To that aim, we evaluated the effects of HOXC4, a protein encoded by a HOXB4 paralog gene, by co-culturing HOXC4-producing stromal cells with human CD34(+) hematopoietic cells. Numbers of progenitors and stem cells were assessed by in vitro cloning assays and injection into immuno-deficient mice, respectively. We also looked for activation or inhibition of target downstream gene expression. RESULTS: We show that the HOXC4 homeoprotein expands human hematopoietic immature cells by 3 to 6 times ex vivo and significantly improves the level of in vivo engraftment. Comparative transcriptome analysis of CD34(+) cells subjected or not to HOXB4 or HOXC4 demonstrated that both homeoproteins regulate the same set of genes, some of which encode key hematopoietic factors and signaling molecules. Certain molecules identified herein are factors reported to be involved in stem cell fate or expansion in other models, such as MEF2C, EZH2, DBF4, DHX9, YPEL5 and Pumilio. CONCLUSIONS: The present study may help to identify new HOX downstream key factors potentially involved in hematopoietic stem cell expansion or in leukemogenesis.
Subject(s)
Hematopoietic Stem Cells/physiology , Homeodomain Proteins/genetics , Homeodomain Proteins/metabolism , Transcription Factors/genetics , Transcription Factors/metabolism , Animals , Cell Proliferation , Cells, Cultured , Coculture Techniques , HEK293 Cells , Humans , Mice , Mice, Inbred NOD , Mice, SCIDABSTRACT
Resistance to chemotherapy, a major therapeutic challenge in the treatment of T-cell acute lymphoblastic leukemia (T-ALL), can be driven by interactions between leukemic cells and the microenvironment that promote survival of leukemic cells. The bone marrow, an important leukemia niche, has low oxygen partial pressures that highly participate in the regulation of normal hematopoiesis. Here we show that hypoxia inhibits T-ALL cell growth by slowing down cell cycle progression, decreasing mitochondria activity, and increasing glycolysis, making them less sensitive to antileukemic drugs and preserving their ability to initiate leukemia after treatment. Activation of the mammalian target of rapamycin (mTOR) was diminished in hypoxic leukemic cells, and treatment of T-ALL with the mTOR inhibitor rapamycin in normoxia mimicked the hypoxia effects, namely decreased cell growth and increased quiescence and drug resistance. Knocking down (KD) hypoxia-induced factor 1α (HIF-1α), a key regulator of the cellular response to hypoxia, antagonized the effects observed in hypoxic T-ALL and restored chemosensitivity. HIF-1α KD also restored mTOR activation in low O2 concentrations, and inhibiting mTOR in HIF1α KD T-ALL protected leukemic cells from chemotherapy. Thus, hypoxic niches play a protective role of T-ALL during treatments. Inhibition of HIF-1α and activation of the mTORC1 pathway may help suppress the drug resistance of T-ALL in hypoxic niches.
Subject(s)
Pharmaceutical Preparations , Precursor T-Cell Lymphoblastic Leukemia-Lymphoma , Drug Resistance, Neoplasm , Humans , Hypoxia , Mechanistic Target of Rapamycin Complex 1 , Precursor T-Cell Lymphoblastic Leukemia-Lymphoma/drug therapy , Tumor MicroenvironmentABSTRACT
BACKGROUND: Quarantine/confinement is an effective measure to face the Coronavirus disease 2019 (COVID-19). Consequently, in response to this stressful situation, people confined to their homes may change their everyday eating behavior. Therefore, the primary objective of this study is to evaluate the association between quarantine/confinement stressors and eating behavior during the COVID-19 outbreak. The secondary objective is to compare the association of quarantine/confinement stressors and diet behavior between two groups of participants, those attending diet clinics and those not (general population). METHOD: A cross-sectional web-based online survey carried out between April 3 and 18, 2020, enrolled 407 participants from the Lebanese population. Eating Disorder Examination - Questionnaire (EDE-Q) were used to measure the behavioral features of eating disorders. RESULTS: More than half of the sample (53.0%) abide by the home quarantine/confinement, 95.4% were living with someone in the quarantine/confinement, and 39.6% continued to work from home. Higher fear of COVID-19 was found in 182 (44.8%) participants, higher boredom in 200 (49.2%) participants, higher anger in 187 (46.3%), and higher anxiety in 197 (48.5%) participants. Higher fear of COVID-19 (Beta = 0.02), higher BMI (Beta = 0.05), and physical activity (Beta = 1.04) were significantly associated with a higher restraint score. Higher anxiety, higher fear of COVID-19, higher BMI, practicing physical exercise, and a higher number of adults living in the quarantine/confinement were significantly associated with higher shape and weight concerns. CONCLUSION: Our results showed that the fear of COVID-19 was correlated with more eating restraint, weight, and shape concerns in the whole sample, but more specifically in the dietitian clients group. Public health control measures are needed to reduce the detrimental effects of psychological distress associated with quarantine/confinement on eating behaviors during the COVID-19 outbreak.
ABSTRACT
The HOXB4 homeoprotein is known to promote the expansion of mouse and human hematopoietic stem cells (HSCs) and progenitors of the myeloid lineages. However, the putative involvement of HOXB4 in lymphopoiesis and particularly in the expansion of early lymphoid progenitor cells has remained elusive. Based on the ability of the HOXB4 protein to passively enter hematopoietic cells, our group previously designed a long-term culture procedure of human HSCs that allows ex vivo expansion of these cells. Here, this method has been further used to investigate whether HOXB4 could cause similar expansion on cells originating from CD34(+) hematopoietic progenitor cells (HPCs) committed at various levels toward the lymphoid lineages. We provide evidence that HOXB4 protein delivery promotes the expansion of primitive HPCs that generate lymphoid progenitors. Moreover, HOXB4 acts on lymphomyeloid HPCs and committed T/natural killer HPCs but not on primary B-cell progenitors. Our results clarify the effect of HOXB4 in the early stages of human lymphopoiesis, emphasizing the contribution of this homeoprotein in the maintenance of the intrinsic lymphomyeloid differentiation potential of defined HPC subsets. Finally, this study supports the potential use of HOXB4 protein for HSC and HPC expansion in a therapeutic setting and furthers our understanding of the mechanisms of the molecular regulation of hematopoiesis.
Subject(s)
Hematopoietic Stem Cells/cytology , Homeodomain Proteins/physiology , Lymphopoiesis/physiology , Transcription Factors/physiology , Animals , Antigens, CD/metabolism , B-Lymphocytes/cytology , B-Lymphocytes/drug effects , B-Lymphocytes/physiology , Cell Differentiation , Cell Line , Coculture Techniques , Colony-Forming Units Assay , Hematopoietic Stem Cells/drug effects , Hematopoietic Stem Cells/physiology , Homeodomain Proteins/genetics , Homeodomain Proteins/pharmacology , Humans , Killer Cells, Natural/cytology , Killer Cells, Natural/drug effects , Killer Cells, Natural/physiology , Lymphopoiesis/drug effects , Mice , Phenotype , Recombinant Proteins/genetics , Recombinant Proteins/pharmacology , T-Lymphocytes/cytology , T-Lymphocytes/drug effects , T-Lymphocytes/physiology , Transcription Factors/genetics , Transcription Factors/pharmacology , Transduction, GeneticABSTRACT
Hypoxia plays a major role in the physiology of hematopoietic and immune niches. Important clues from works in mouse have paved the way to investigate the role of low O2 levels in hematopoiesis. However, whether hypoxia impacts the initial steps of human lymphopoiesis remains unexplored. Here, we show that hypoxia regulates cellular and metabolic profiles of umbilical cord blood (UCB)-derived hematopoietic progenitor cells. Hypoxia more specifically enhances in vitro lymphoid differentiation potentials of lymphoid-primed multipotent progenitors (LMPPs) and pro-T/natural killer (NK) cells and in vivo B cell potential of LMPPs. In accordance, hypoxia exacerbates the lymphoid gene expression profile through hypoxia-inducible factor (HIF)-1α (for LMPPs) and HIF-2α (for pro-T/NK). Moreover, loss of HIF-1/2α expression seriously impedes NK and B cell production from LMPPs and pro-T/NK. Our study describes how hypoxia contributes to the lymphoid development of human progenitors and reveals the implication of the HIF pathway in LMPPs and pro-T/NK-cell lymphoid identities.
Subject(s)
Cell Hypoxia/physiology , Hematopoietic Stem Cells/cytology , Hematopoietic Stem Cells/metabolism , Lymphoid Progenitor Cells/cytology , Lymphoid Progenitor Cells/metabolism , B-Lymphocytes/cytology , B-Lymphocytes/metabolism , Basic Helix-Loop-Helix Transcription Factors/genetics , Basic Helix-Loop-Helix Transcription Factors/metabolism , Cell Differentiation/genetics , Cell Differentiation/physiology , Cell Hypoxia/genetics , Cells, Cultured , Humans , Hypoxia-Inducible Factor 1, alpha Subunit/genetics , Hypoxia-Inducible Factor 1, alpha Subunit/metabolism , Killer Cells, Natural/cytology , Killer Cells, Natural/metabolism , Lymphopoiesis/genetics , Lymphopoiesis/physiology , Oxygen/metabolismABSTRACT
The ETS-domain transcription factors divide into subfamilies based on protein similarities, DNA-binding sequences, and interaction with cofactors. They are regulated by extracellular clues and contribute to cellular processes, including proliferation and transformation. ETS genes are targeted through genomic rearrangements in oncogenesis. The PU.1/SPI1 gene is inactivated by point mutations in human myeloid malignancies. We identified a recurrent somatic mutation (Q226E) in PU.1/SPI1 in Waldenström macroglobulinemia, a B-cell lymphoproliferative disorder. It affects the DNA-binding affinity of the protein and allows the mutant protein to more frequently bind and activate promoter regions with respect to wild-type protein. Mutant SPI1 binding at promoters activates gene sets typically promoted by other ETS factors, resulting in enhanced proliferation and decreased terminal B-cell differentiation in model cell lines and primary samples. In summary, we describe oncogenic subversion of transcription factor function through subtle alteration of DNA binding leading to cellular proliferation and differentiation arrest. SIGNIFICANCE: The demonstration that a somatic point mutation tips the balance of genome-binding pattern provides a mechanistic paradigm for how missense mutations in transcription factor genes may be oncogenic in human tumors.This article is highlighted in the In This Issue feature, p. 681.
Subject(s)
Gene Expression Regulation , Mutation, Missense , Proto-Oncogene Proteins c-ets/genetics , Proto-Oncogene Proteins/metabolism , Trans-Activators/metabolism , Waldenstrom Macroglobulinemia/genetics , Waldenstrom Macroglobulinemia/metabolism , Animals , Azepines/pharmacology , B-Lymphocytes/cytology , B-Lymphocytes/metabolism , Base Sequence , Binding Sites , Cell Line , Cell Proliferation , Humans , Lenalidomide/pharmacology , Mice , Myeloid Differentiation Factor 88/genetics , Myeloid Differentiation Factor 88/metabolism , Nucleotide Motifs , Protein Binding , Proto-Oncogene Proteins/genetics , Proto-Oncogene Proteins c-ets/metabolism , Trans-Activators/genetics , Transcription Factors/metabolism , Triazoles/pharmacology , Waldenstrom Macroglobulinemia/diagnosisABSTRACT
Hematopoiesis generated from human embryonic stem cells (ES) and induced pluripotent stem cells (iPS) are unprecedented resources for cell therapy. We compared hematopoietic differentiation potentials from ES and iPS cell lines originated from various donors and derived them using integrative and non-integrative vectors. Significant differences in differentiation toward hematopoietic lineage were observed among ES and iPS. The ability of engraftment of iPS or ES-derived cells in NOG mice varied among the lines with low levels of chimerism. iPS generated from ES cell-derived mesenchymal stem cells (MSC) reproduce a similar hematopoietic outcome compared to their parental ES cell line. We were not able to identify any specific hematopoietic transcription factors that allow to distinguish between good versus poor hematopoiesis in undifferentiated ES or iPS cell lines. There is a relatively unpredictable variation in hematopoietic differentiation between ES and iPS cell lines that could not be predicted based on phenotype or gene expression of the undifferentiated cells. These results demonstrate the influence of genetic background in variation of hematopoietic potential rather than the reprogramming process.
Subject(s)
Cellular Reprogramming/genetics , Embryonic Stem Cells/cytology , Genetic Heterogeneity , Graft Survival , Hematopoiesis/genetics , Induced Pluripotent Stem Cells/cytology , Animals , Biomarkers/metabolism , Cell Differentiation , Cell Line , Cell Lineage/genetics , Chimerism , Embryonic Stem Cells/metabolism , Embryonic Stem Cells/transplantation , Gene Expression , Genetic Vectors , Humans , Induced Pluripotent Stem Cells/metabolism , Induced Pluripotent Stem Cells/transplantation , Lentivirus/genetics , Mice , Mice, Inbred NOD , Mice, SCID , Retroviridae/genetics , Tissue Donors , Transcription Factors/genetics , Transcription Factors/metabolism , Transplantation, HeterologousABSTRACT
During human embryonic stem cell (ESC) hematopoietic differentiation, the description of the initial steps of lymphopoiesis remains elusive. Using a two-step culture procedure, we identified two original populations of ESC-derived hematopoietic progenitor cells (HPCs) with CD34(+)CD45RA(+)CD7(-) and CD34(+)CD45RA(+)CD7(+) phenotypes. Bulk cultures and limiting dilution assays, culture with MS5 cells in the presence of Notch ligand Delta-like-1 (DL-1), and ex vivo colonization tests using fetal thymic organ cultures showed that although CD34(+)CD45RA(+)CD7(-) HPCs could generate cells of the three lymphoid lineages, their potential was skewed toward the B cell lineages. In contrast, CD34(+)CD45RA(+)CD7(+) HPCs predominantly exhibited a T/natural killer (NK) cell differentiation potential. Furthermore these cells could differentiate equivalently into cells of the granulo-macrophagic lineage and dendritic cells and lacked erythroid potential. Expression profiling of 18 markers by quantitative reverse transcription-polymerase chain reaction (qRT-PCR) revealed that CD34(+)CD45RA(+)CD7(-) and CD34(+)CD45RA(+)CD7(+) HPCs express genes of the lymphoid specification and that CD34(+)CD45RA(+)CD7(-) cells express B-cell-associated genes, while CD34(+)CD45RA(+)CD7(+) HPCs display a T-cell molecular profile. Altogether, these findings indicate that CD34(+)CD45RA(+)CD7(-) and CD34(+)CD45RA(+)CD7(+) HPCs correspond to candidate multipotent early lymphoid progenitors polarized toward either the B or T/NK lineage, respectively. This work should improve our understanding of the early steps of lymphopoiesis from pluripotent stem cells and pave the way for the production of lymphocytes for cell-based immunotherapy and lymphoid development studies.
Subject(s)
Embryonic Stem Cells/cytology , Hematopoiesis , Lymphoid Progenitor Cells/cytology , Pluripotent Stem Cells/cytology , Animals , Antigens, CD/genetics , Antigens, CD/metabolism , Calcium-Binding Proteins , Cell Line , Cell Lineage , Cells, Cultured , Embryonic Stem Cells/metabolism , Humans , Intercellular Signaling Peptides and Proteins/genetics , Intercellular Signaling Peptides and Proteins/metabolism , Lymphoid Progenitor Cells/metabolism , Membrane Proteins/genetics , Membrane Proteins/metabolism , Mice , Mice, Inbred NOD , Pluripotent Stem Cells/metabolismABSTRACT
Human embryonic stem cells (hESCs) can be induced to differentiate into blood cells using either co-culture with stromal cells or following human embryoid bodies (hEBs) formation. It is now well established that the HOXB4 homeoprotein promotes the expansion of human adult hematopoietic stem cells (HSCs) but also myeloid and lymphoid progenitors. However, the role of HOXB4 in the development of hematopoietic cells from hESCs and particularly in the generation of hESC-derived NK-progenitor cells remains elusive. Based on the ability of HOXB4 to passively enter hematopoietic cells in a system that comprises a co-culture with the MS-5/SP-HOXB4 stromal cells, we provide evidence that HOXB4 delivery promotes the enrichment of hEB-derived precursors that could differentiate into fully mature and functional NK. These hEB-derived NK cells enriched by HOXB4 were characterized according to their CMH class I receptor expression, their cytotoxic arsenal, their expression of IFNγ and CD107a after stimulation and their lytic activity. Furthermore our study provides new insights into the gene expression profile of hEB-derived cells exposed to HOXB4 and shows the emergence of CD34(+)CD45RA(+) precursors from hEBs indicating the lymphoid specification of hESC-derived hematopoietic precursors. Altogether, our results outline the effects of HOXB4 in combination with stromal cells in the development of NK cells from hESCs and suggest the potential use of HOXB4 protein for NK-cell enrichment from pluripotent stem cells.
Subject(s)
Cell Differentiation/physiology , Embryonic Stem Cells/metabolism , Homeodomain Proteins/metabolism , Killer Cells, Natural/metabolism , Transcription Factors/metabolism , Cell Line , Coculture Techniques , Embryonic Stem Cells/cytology , Homeodomain Proteins/genetics , Humans , Killer Cells, Natural/cytology , Stromal Cells/cytology , Stromal Cells/metabolism , Transcription Factors/geneticsABSTRACT
Human embryonic stem cells (hESCs) can be induced to differentiate towards hematopoiesis with high efficiency. In this work, we analyzed the methylation status of the X-linked HUMARA (human androgen receptor) gene in hematopoietic cells derived from hESC line H9 before and after induction of hematopoietic differentiation. All passages of H9 and H9-derived hematopoietic cells displayed homogenous methylation pattern with disappearance of the same allele upon HpaII digestion. This pattern persisted in the great majority of different hematopoietic progenitors derived from H9, except in 11 of 86 individually plucked colonies in which an equal digestion of the HUMARA alleles has been found, suggesting that a methylation change occurring at this locus during differentiation. Interestingly, quantification of X inactive-specific transcript (XIST) RNA in undifferentiated H9 cell line and day 14 embryoid bodies (EB) by RT-PCR did not show any evidence of XIST expression either before or after differentiation. Thus, during self-renewal conditions and after induction of commitment towards the formation of EB, the methylation pattern of the HUMARA locus appears locked with the same unmethylated allele. However, hematopoietic differentiation seems to be permissive to the reversal of methylation status of HUMARA in some terminally differentiated progenitors. These data suggest that monitoring methylation of HUMARA gene during induced differentiation could be of use for studying hESC-derived hematopoiesis.
Subject(s)
DNA Methylation , Embryonic Stem Cells/cytology , Genes, X-Linked , Hematopoiesis , Hematopoietic Stem Cells/cytology , Receptors, Androgen/genetics , Cell Line , Embryonic Stem Cells/metabolism , Hematopoietic Stem Cells/metabolism , Humans , Receptors, Androgen/metabolismABSTRACT
Here, we identify fetal bone marrow (BM)-derived CD34hiCD45RAhiCD7+ hematopoietic progenitors as thymus-colonizing cells. This population, virtually absent from the fetal liver (FL), emerges in the BM by development weeks 8-9, where it accumulates throughout the second trimester, to finally decline around birth. Based on phenotypic, molecular, and functional criteria, we demonstrate that CD34hiCD45RAhiCD7+ cells represent the direct precursors of the most immature CD34hiCD1a- fetal thymocytes that follow a similar dynamics pattern during fetal and early postnatal development. Histological analysis of fetal thymuses further reveals that early immigrants predominantly localize in the perivascular areas of the cortex, where they form a lymphostromal complex with thymic epithelial cells (TECs) driving their rapid specification toward the T lineage. Finally, using an ex vivo xenogeneic thymus-colonization assay, we show that BM-derived CD34hiCD45RAhiCD7+ progenitors are selectively recruited into the thymus parenchyma in the absence of exogenous cytokines, where they adopt a definitive T cell fate.
Subject(s)
B-Lymphocytes/immunology , Bone Marrow/embryology , Cell Movement , Hematopoietic Stem Cells/physiology , Thymus Gland/embryology , Animals , Antigens, CD/metabolism , Antigens, Differentiation, T-Lymphocyte/metabolism , B-Lymphocytes/physiology , Bone Marrow/metabolism , Cell Differentiation , Humans , Mice , Mice, Transgenic , Organ Culture Techniques , Phenotype , Thymus Gland/cytology , Thymus Gland/immunologyABSTRACT
A novel membrane protein has been identified in the course of screening for differentially expressed cDNAs in human embryonic hematopoietic sites. This 37- to 38-kDa molecule, designated KLIP-1 (killer lineage protein), consisting of 350 amino acids and containing five transmembrane domains, is encoded by the 5093-bp KLIP-1 gene, composed of nine exons and located on chromosome 6 (6p21.1-6p21.2). We found the KLIP-1 protein to be expressed by nucleated hematopoietic cells, from early embryonic hematopoietic stem cells through mature adult blood lymphoid lineages, either as membrane or as cytoplasmic molecules. In day-30/32 human embryo sections, KLIP-1 protein expression is restricted to circulating hematopoietic cells at hematopoiesis sites. Membrane KLIP-1 is expressed by fetal and adult GP-A(+) erythroblasts, the fetal liver CD34(+) subset, fetal spleen, and adult bone marrow CD56(+) NK and CD19(+) B cells. Among mature blood cells, surface KLIP-1 expression is restricted to CD56(+) NK cells, indicating KLIP-1 to be a novel marker of this population. Altogether, these results indicate that membrane export of KLIP-1 antigen is developmentally and ontogenetically regulated. The high degree of conservation of the KLIP-1 protein sequence among mammals strongly suggests that it plays an important role during hematopoiesis and may exercise similar functions in human and mouse blood cells. The KLIP-1 molecule may therefore constitute a powerful tool for improving knowledge of both human hematopoiesis and NK cell ontogeny and immune functions.
Subject(s)
Cell Lineage , Embryo, Mammalian/cytology , Hematopoiesis , Hematopoietic Stem Cells/cytology , Membrane Proteins/physiology , Adult , Amino Acid Sequence , Animals , Antigens, CD34 , Biomarkers , Chromosome Mapping , Embryo, Mammalian/chemistry , Gene Expression Profiling , Gene Expression Regulation, Developmental , Humans , Membrane Proteins/chemistry , Membrane Proteins/genetics , Molecular Sequence Data , Tissue DistributionABSTRACT
The early stages of human lymphopoiesis are poorly characterized. Here, we compared the lymphoid potential of a novel umbilical cord blood CD34(+)CD45RA(hi)CD7(+) hematopoietic progenitor cell (HPC) population with that of CD34(+)CD45RA(hi)Lin(-)CD10(+) HPCs, previously proposed as candidate common lymphoid progenitors. Limiting-dilution and clonal analysis, fetal thymic organ cultures, and culture onto Notch ligand Delta-like-1-expressing OP9 cells, showed that although CD34(+)CD45RA(hi)CD7(+) HPCs could generate cells of the 3 lymphoid lineages, their potential was skewed toward the T/natural killer (T/NK) lineages. In contrast, CD34(+)CD45RA(hi)Lin(-)CD10(+) HPCs predominantly exhibited a B-cell potential. Gene expression profiling with DNA microarrays confirmed that CD34(+)CD45RA(hi)CD7(+) HPCs selectively expressed T-lymphoid and NK lineage-committed genes while retaining expression of genes affiliated to the granulomonocytic lineage, whereas CD34(+)CD45RA(hi)Lin(-)CD10(+) HPCs displayed a typical pro-B-cell transcription profile and essentially lacked genes unrelated to the B lineage. In addition, both populations could be generated in vitro from CD34(+)CD45RA(int)CD7(-) and CD34(+)CD45RA(hi)Lin(-) HPCs with mixed lymphomyeloid potential, from which they emerged independently with different growth/differentiation factor requirements. These findings indicate that CD34(+)CD45RA(hi)CD7(+) and CD34(+)CD45RA(hi)Lin(-)CD10(+) HPCs correspond to multipotent early lymphoid progenitors polarized toward either the T/NK or B lineage, respectively.