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MYB is an essential regulator of primitive human hematopoiesis in human pluripotent stem cell differentiation cultures.

ABSTRACT: MYB is well recognized to be a key regulator of definitive hematopoiesis that plays an important role in the maintenance and multilineage differentiation of hematopoietic stem cells (HSCs). In the vertebrate developmental context, MYB is widely regarded dispensable for primitive hematopoiesis but critically required for the development of definitive hematopoiesis. To explore the role of MYB in human hematopoietic development we have inactivated the gene by bi-allelic TALEN-supported gene targeting in several lines of human embryonic stem cells (hESCs) and induced pluripotent stem cells (iPSCs), and subjected these cells to hematopoietic differentiation in well-defined cell culture conditions. Venus gene reporter was inserted into the knock-in allele to monitor MYB expression during the course of the hESC/iPSC differentiation. The gene reporter system showed that MYB is specifically expressed during hematopoietic commitment in the earliest primitive blood cells. Moreover, the level of MYB expression was highest at the commitment stage of differentiation and significantly decreased at the maturations stage. We found that MYB was not required for initial hematopoietic commitment of nascent mesoderm and emergence of primitive, yolk sac-type human hematopoietic progenitors. However, inactivation of MYB severely abrogated proliferation of the primitive erythroid and mixed erythroid-macrophage-megakaryocyte progenitors. In addition, MYB-negative hESC/iPSC lines demonstrated major defects in myeloid cell development and completely failed to generate mature granulocytes. Transposon-mediated rescue of MYB expression in MYB-null cells efficiently restored both the primitive hematopoietic progenitors and immature myeloid cells. Our data indicate that in contrast to its previously attributed exclusive role in definitive hematopoiesis, MYB is indispensable for primitive human hematopoiesis.

ORGANISM(S): Homo sapiens

PROVIDER: GSE125761 | GEO | 2021/01/31

REPOSITORIES: GEO

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Project description:The realization of human embryonic stem cells (hESC) as a model for human developmental hematopoiesis and potential cell replacement strategies relies on an improved understanding of the extrinsic and intrinsic factors regulating hematopoietic-specific hESC differentiation. Mesenchymal stem cells (hMSCs) are multipotent cells of mesodermal origin that form part of hematopoietic stem cell niches and have an important role in the regulation of hematopoiesis through production of secreted factors and/or cell-to-cell interactions. We have previously shown that hESCs may be successfully maintained feeder-free using hMSC-conditioned media (MSC-CM). Here, we hypothesized that hESCs maintained in MSC-CM may be more prone to differentiation towards hematopoietic lineage than hESCs grown in standard human foreskin fibroblast (HFF)-conditioned media (HFF-CM). We report that specification into hemogenic progenitors and subsequent hematopoietic differentiation and clonogenic progenitor capacity is robustly enhanced in hESC lines maintained in MSC-CM. Interestingly, co-culture of hESCs on hMSCs fully abrogates hematopoietic specification of hESCs suggesting that the improved hematopoietic differentiation is mediated by MSC-secreted factors rather than by MSC-hESC physical interactions. To investigate the molecular mechanism involved in this process, we analyzed global (LINE-1) methylation and genome-wide promoter DNA methylation. Human ESCs grown in MSC-CM showed a decrease of 20% in global DNA methylation and a promoter DNA methylation signature consisting in 45 genes commonly hypomethylated and 102 genes frequently hypermethylated. Our data indicate that maintenance of hESCs in MSC-CM robustly augments hematopoietic specification and that the process seems mediated by MSC-secreted factors conferring a DNA methylation signature to undifferentiated hESCs which may influence further predisposition towards hematopoietic specification. Total DNA isolated by standard procedures from human embryonic stem cells (hESC) cultured in different conditioned media

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MYB is an essential regulator of primitive human hematopoiesis in human pluripotent stem cell differentiation cultures.

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