Tel1/ETV6 Specifies Blood Stem Cells through the Agency of VEGF Signaling

SummaryThe regulation of stem cell ontogeny is poorly understood. We show that the leukemia-associated Ets transcription factor, Tel1/ETV6, specifies the first hematopoietic stem cells (HSCs) in the dorsal aorta (DA). In contrast, Tel1/ETV6 has little effect on embryonic blood formation, further distinguishing the programming of the long- and short-term blood populations. Consistent with the notion of concordance of arterial and HSC programs, we show that Tel1/ETV6 is also required for the specification of the DA as an artery. We further show that Tel1/ETV6 acts by regulating the transcription of VegfA in both the lateral plate mesoderm and also in the somites. Exogenous VEGFA rescues Tel1/ETV6 morphants, and depletion of VEGFA or its receptor, Flk1, largely phenocopies Tel1/ETV6 depletion. Few such links between intrinsic and extrinsic programming of stem cells have been reported previously. Our data place Tel1/ETV6 at the apex of the genetic regulatory cascade leading to HSC production.

Graphical AbstractFigure optionsDownload full-size imageDownload high-quality image (247 K)Download as PowerPoint slideHighlights► Tel1/ETV6 is required for the formation of the first hematopoietic stem cells (HSCs) in the dorsal aorta (DA) ► Tel1/ETV6 is also required for arterial programming of the DA ► Tel1/ETV6 drives vascular endothelial growth factor (VEGF) production in both HSC precursors and the adjacent somites ► Programming of HSC precursors requires both paracrine VEGF signaling from the somites and autocrine signaling from within the HSC precursors themselves