Hematopoietic stem cell fate is established by the Notch–Runx pathway

Abstract

Identifying the molecular pathways regulating hematopoietic stem cell (HSC) specification, self-renewal, and expansion remains a fundamental goal of both basic and clinical biology. Here, we analyzed the effects of Notch signaling on HSC number during zebrafish development and adulthood, defining a critical pathway for stem cell specification. The Notch signaling mutant mind bomb displays normal embryonic hematopoiesis but fails to specify adult HSCs. Surprisingly, transient Notch activation during embryogenesis via an inducible transgenic system led to a Runx1-dependent expansion of HSCs in the aorta-gonad-mesonephros (AGM) region. In irradiated adults, Notch activity induced runx1 gene expression and increased multilineage hematopoietic precursor cells approximately threefold in the marrow. This increase was followed by the accelerated recovery of all the mature blood cell lineages. These data define the Notch-Runx pathway as critical for the developmental specification of HSC fate and the subsequent homeostasis of HSC number, thus providing a mechanism for amplifying stem cells in vivo.[Keywords: Stem cell; Notch; Runx; AGM; zebrafish; irradiation] Supplemental material is available at http://www.genesdev.org.

AML1/Runx1 rescues Notch1-null mutation-induced deficiency of para-aortic splanchnopleural hematopoiesis

“…9 Importantly, presence of the NotchRunx pathway has been proposed in Drosophila embryonic hemocytogenesis 10 and zebrafish hematopoiesis during both developmental and postnatal periods. 11 Similarly reported has been transcriptional regulation by Notch of the Gata2 gene in mouse AGM hematopoiesis 8 and of the Gata homolog Serpent gene in Drosophila embryonic hemocytogenesis. 12 In mammals, the existence of Notch-Runx pathway has been unclear.…”

“…10,11 We thus first evaluated whether Notch activation results in up-regulation of Runx1 also in the mammalian system. When NIH3T3 cells were transiently transfected with Notch1 intracellular domain (NICD), which represents the constitutive active form of Notch1, the mRNA level of Runx1 increased (Table 1).…”

Gamma-secretase inhibitors target tumor-initiating cells in a mouse model of ERBB2 breast cancer

“…Table 1 illustrates that several Notch-related genes were overexpressed in tumorspheres compared with mammospheres. The latter included genes encoding Notch pathway components (notch4, dtx1, dll1 and tle); target genes (hey1, runx1, krt1 and il17b); as well as lfng and mmp7, which encode proteins required for Notch glycosylation and intramembrane proteolysis (Matsuno et al, 1995;Burns et al, 2005;Sawey et al, 2007;Sawey and Crawford, 2008;Zhang et al, 2010). These findings suggested that the Notch pathway might be more active in tumorspheres compared with mammospheres.…”

Co-injection strategies to modify radiation sensitivity and tumor initiation in transgenic Zebrafish

“…Heat-shock-inducible transgenic approaches have provided an invaluable tool through which gene expression in development can be modulated (Halloran et al, 2000;Xiao et al, 2003;Burns et al, 2005;Pyati et al, 2005). To establish if co-injection techniques along with heat-shock-inducible transgenesis could be used to elicite gene expression within established tumors, the rag2-kRASG12D, rag2-GFP and hsp70-dsRED2 constructs were co-injected into one-cell stage AB-strain animals.…”