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Inflammatory signaling regulates hematopoietic stem and progenitor cell emergence in vertebrates

Qiuping He, Chunxia Zhang, Lu Wang, Panpan Zhang, Dongyuan Ma, Junhua Lv and Feng Liu

Key Points

  • TLR4–MyD88–NF-κB is required for HSPC emergence in zebrafish and mouse embryos.

  • Notch functions downstream of inflammatory signaling to regulate HSPC emergence.

Abstract

Inflammatory signaling has been shown to be essential for stress hematopoiesis in adult bone marrow, either through increasing proliferation or by directing differentiation of hematopoietic stem and progenitor cells (HSPCs) toward myeloid or lymphoid lineages. However, its role in embryonic normal hematopoiesis has been unknown. Here, we demonstrate that in both zebrafish and mouse embryos, inflammatory signaling is necessary and sufficient for HSPC emergence, in the absence of infection or pathological inflammation. Mechanistically, inflammatory signaling regulates hemogenic endothelium-derived HSPC development through a conserved Toll-like receptor 4 (TLR4)–nuclear factor κ-light-chain enhancer of activated B core (NF-κB) signaling, which then promotes Notch activity, a well-known signal required for HSPC specification in vertebrates. Our findings establish a previously unrecognized link between inflammatory signaling and HSPC emergence, and provide new insights into regenerative medicine and novel therapies to treat innate immune-related diseases.

  • Submitted September 15, 2014.
  • Accepted December 22, 2014.
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