Dataset Information

Hedgehog and Bmp polarize hematopoietic stem cell emergence in the zebrafish dorsal aorta.

ABSTRACT: Hematopoietic stem cells (HSCs) are first detected in the floor of the embryonic dorsal aorta (DA), and we investigate the signals that induce the HSC program there. We show that while continued Hedgehog (Hh) signaling from the overlying midline structures maintains the arterial program characteristic of the DA roof, a ventral Bmp4 signal induces the blood stem cell program in the DA floor. This patterning of the DA by Hh and Bmp is the mirror image of that in the neural tube, with Hh favoring dorsal rather than ventral cell types, and Bmp favoring ventral rather than dorsal. With the majority of current data supporting a model whereby HSCs derive from arterial endothelium, our data identify the signal driving this conversion. These findings are important for the study of the production of HSCs from embryonic stem cells and establish a paradigm for the development of adult stem cells.

SUBMITTER: Wilkinson RN

PROVIDER: S-EPMC3210643 | biostudies-other | 2009 Jun

REPOSITORIES: biostudies-other

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Hedgehog and Bmp polarize hematopoietic stem cell emergence in the zebrafish dorsal aorta.

Wilkinson Robert N RN Pouget Claire C Gering Martin M Russell Angela J AJ Davies Stephen G SG Kimelman David D Patient Roger R

Developmental cell 20090601 6

Hematopoietic stem cells (HSCs) are first detected in the floor of the embryonic dorsal aorta (DA), and we investigate the signals that induce the HSC program there. We show that while continued Hedgehog (Hh) signaling from the overlying midline structures maintains the arterial program characteristic of the DA roof, a ventral Bmp4 signal induces the blood stem cell program in the DA floor. This patterning of the DA by Hh and Bmp is the mirror image of that in the neural tube, with Hh favoring d ...[more]

PMID: 19531361

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Project description:During embryonic development, the first hematopoietic stem cells (HSCs) arise from a transient population of endothelial cells lining the ventral surface of the dorsal aorta, via a process of endothelial to hematopoietic transition (EHT) at embryonic day (E) 10.5. This region contains resident PDGFRA+ stromal cells (PSCs), but their identity and role in HSC generation in the AGM are not well understood. Using a library of compound transgenic mice, we identified a population of PDGFRA+/Nestin-GFP (N-GFP)-/PDGFRB-/CD31- cells with PSC activity in the E10.5 and E11.5 mouse AGM. Freshly isolated PSCs were adept at forming blood vessels with CD31+ luminal endothelium enveloped by PDGFRB+ pericytes, when transplanted subcutaneously into mice. Conditional ablation of PDGFRA+ or Nestin+ cells led to either complete or partial loss of PSCs respectively, with severe loss of endothelial and pericyte-like cells, and concomitant loss of blood formation in the AGM. Lineage tracing studies using tamoxifen induction in PDGFRACreERT2/R26eYFP embryos showed that stromal, sub-endothelial, endothelial and long-term repopulating hematopoietic stem cells (LT-HSCs) cells in the E11.5 AGM were progeny of PDGFRA cells. Using transgenic reporter mice, we showed that MesP1 (mesoderm) derived PDGFRA+ cells dominated the sub-endothelial and deeper ventral stroma in the AGM at E10.5 and E11.5 but were replaced by Wnt1 (neural crest) derived cells at E13.5. Re-aggregation of E11.5 Mesp1 derived PSC cells with E13.5 aortic or adult cardiac non-hemogenic endothelial cells resulted in the generation of endothelial cell derived LT-HSCs. RNA-sequencing analysis of non-hemogenic E13.5 endothelial cells showed up-regulation of EHT genes, WNT, BMP and Notch cell signalling pathways when re-aggregated with E11.5 Mesp1 derived PSCs. LT-HSC generation from these re-aggregates was suppressed by dose-dependent inhibition of PDGF-AA/PDGFRA signalling. Taken together, we report that PSC populations in the AGM are temporally dynamic, and that MesP1-derived PSCs regulate hemogenic potential of the endothelium and that this cooperativity is dependent on PDGF-AA/PDGFRA signalling. This submission represents the RNAseq component of the study.

Dataset Information

Hedgehog and Bmp polarize hematopoietic stem cell emergence in the zebrafish dorsal aorta.

Publications

Hedgehog and Bmp polarize hematopoietic stem cell emergence in the zebrafish dorsal aorta.

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