Transcription factor Maf promotes expression of repressor Zeb2 to drive microglia development in primitive hematopoiesis.

Hemangioblast, hemogenic endothelium, and primitive versus definitive hematopoiesis.

Bef medaka mutant reveals the essential role of c-myb in both primitive and definitive hematopoiesis

Generation of definitive hematopoietic progenitors from human pluripotent stem cells

Identification of Three Phases of Hematopoieisis in Zebrafish and Their Differential Requirements for Runx1 and Gata1 Functions.

SUMMARYEndothelial and erythropoietic lineages arise from a common developmental progenitor. Etv2 is a master transcriptional regulator required for the development of both lineages. However, the mechanisms through which Etv2 initiates the gene-regulatory networks (GRNs) for endothelial and erythropoietic specification and how the two GRNs diverge downstream of Etv2 remain incompletely understood. Here, by analyzing a hypomorphic Etv2 mutant, we demonstrate different threshold requirements for initiation of the downstream GRNs for endothelial and erythropoietic development. We show that Etv2 functions directly in a coherent feedforward transcriptional network for vascular endothelial development, and a low level of Etv2 expression is sufficient to induce and sustain the endothelial GRN. In contrast, Etv2 induces the erythropoietic GRN indirectly via activation of Tal1, which requires a significantly higher threshold of Etv2 to initiate and sustain erythropoietic development. These results provide important mechanistic insight into the divergence of the endothelial and erythropoietic lineages.

Definitive hematopoiesis generates hematopoietic stem/progenitor cells (HSPCs) that give rise to all mature blood and immune cells, but remains poorly defined in human. Here, we resolve human hematopoietic populations at the earliest hematopoiesis stage by single-cell RNA-seq. We characterize the distinct molecular profiling between early primitive and definitive hematopoiesis in both human embryonic stem cell (hESC) differentiation and early embryonic development. We identify CD44 to specifically discriminate definitive hematopoiesis and generate definitive HSPCs from hESCs. The multipotency of hESCs-derived HSPCs for various blood and immune cells is validated by single-cell clonal assay. Strikingly, these hESCs-derived HSPCs give rise to blood and lymphoid lineages in vivo. Lastly, we characterize gene-expression dynamics in definitive and primitive hematopoiesis and reveal an unreported role of ROCK-inhibition in enhancing human definitive hematopoiesis. Our study provides a prospect for understanding human early hematopoiesis and a firm basis for generating blood and immune cells for clinical purposes.

Zebrafish Growth Factor Independence Transcription Factors Establish a New Paradigm for Regulation of Primitive and Definitive Hematopoietic Lineages,

Human microglia are vital residents of the brain, where they play important roles in development, injury and disease, such as Alzheimer's (AD) disease. Arising from yolk sac primitive progenitors that colonize in the brain during embryogenesis, microglia are unique among tissue macrophages in that they are thought to remain primitive progenitors derived throughout life, without contribution from the definitive hematopoiesis. After insults such as stroke and neurodegenerative disease, however, microglia dramatically change their phenotype and are joined by infiltrating macrophages from blood. These definitive hematopoietic progenitors-derived occupants can resemble microglia in morphology and surface marker expression but appear to participate differently in disease pathogenesis, making it essential to further clarify their functions. Currently, there is no method reported to generate these two microglia cells from the same iPSCs. To understand how naive microglia and infiltrating microglia cells affect the brain in disease condition, we developed a novel protocol to efficiently produce two different microglia cells separately from primitive or definitive hematopoietic progenitors. By manipulating WNT signaling and Activin-Nodal signaling, human iPSCs were first induced to separate hematopoietic fates, primitive hematopoietic progenitors (CD43+, CD235a+) and definitive hematopoietic progenitors (CD34+, CD43-, CD235a-). Next, these two hematopoietic progenitors were grown in serum-free differentiation medium containing CSF-1 and IL-34 to differentiate into macrophages, then cocultured with our BrainXell cortical neuron and astrocyte mixed culture to induce microglia identity. We identified the different gene expression between these two microglia cells by RNA-seq profiling, and validated by qPCR, immunostaining and FACS analysis. In summary, two different microglia cells, derived separately from iPSC derived primitive or definitive hematopoietic progenitors, will provide useful models to understanding microglia function in neurological diseases like AD disease.

Differential requirement for Gata1 DNA binding and transactivation between primitive and definitive stages of hematopoiesis in zebrafish

The endothelial antigen ESAM marks primitive hematopoietic progenitors throughout life in mice

Oxidative Stress-Mediated Activation of AKT/mTOR Signaling Pathway Leads to Myeloproliferative Syndrome in FoxO3 Null Mice: A Role for Lnk Adaptor Protein

Efforts to derive hematopoietic stem cells (HSCs) from human pluripotent stem cells (hPSCs) are complicated by the fact that embryonic hematopoiesis consists of two programs, primitive and definitive, that differ in developmental potential. As only definitive hematopoiesis generates HSCs, understanding how this program develops is essential for being able to produce this cell population in vitro. Here we show that both hematopoietic programs transition through hemogenic endothelial intermediates and develop from KDR+CD34−CD144− progenitors that are distinguished by CD235a expression. Generation of primitive progenitors (KDR+CD235a+) depends on stage-specific Activin-nodal signaling and inhibition of the Wnt-β-catenin pathway, whereas specification of definitive progenitors (KDR+CD235a−) requires Wnt-β-catenin signaling during this same time frame. Together, these findings establish simple selective differentiation strategies for the generation of primitive or definitive hematopoietic progenitors via Wnt-β-catenin manipulation, and in doing so provide access to enriched populations for future studies on hPSC-derived hematopoietic development.

Transcription Factors and Hematopoietic Development

The Multimerization Domain of Cbfß-SMMHC Is Required for Leukemogenesis

Direct contact between human primitive hematopoietic progenitors and bone marrow stroma is not required for long-term in vitro hematopoiesis