CBFβ and RUNX1 are required at 2 different steps during the development of hematopoietic stem cells in zebrafish.
CBFβ and RUNX1 form a DNA-binding heterodimer and are both required for hematopoietic stem cell (HSC) generation in mice. However, the exact role of CBFβ in the production of HSCs remains unclear. Here, we generated and characterized 2 zebrafish cbfb null mutants. The cbfb(-/-) embryos underwent primitive hematopoiesis and developed transient erythromyeloid progenitors, but they lacked definitive hematopoiesis. Unlike runx1 mutants, in which HSCs are not formed, nascent, runx1(+)/c-myb(+) HSCs were formed in cbfb(-/-) embryos. However, the nascent HSCs were not released from the aorta-gonad-mesonephros (AGM) region, as evidenced by the accumulation of runx1(+) cells in the AGM that could not enter circulation. Moreover, wild-type embryos treated with an inhibitor of RUNX1-CBFβ interaction, Ro5-3335, phenocopied the hematopoietic defects in cbfb(-/-) mutants, rather than those in runx1(-/-) mutants. Finally, we found that cbfb was downstream of the Notch pathway during HSC development. Our data suggest that runx1 and cbfb are required at 2 different steps during early HSC development. CBFβ is not required for nascent HSC emergence but is required for the release of HSCs from AGM into circulation. Our results also indicate that RUNX1 can drive the emergence of nascent HSCs in the AGM without its heterodimeric partner CBFβ.
Oncogenesis and Development Section.
Erica
E
Bresciani
Zebrafish Core.
Blake
B
Carrington
Cytogenetics and Microscopy Core, and.
Stephen
S
Wincovitch
Genomics Core, National Human Genome Research Institute, National Institutes of Health, Bethesda, MD; and.
MaryPat
M
Jones
Program in Genomics of Differentiation, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD.
Aniket V
AV
Gore
Program in Genomics of Differentiation, National Institute of Child Health and Human Development, National Institutes of Health, Bethesda, MD.
Brant M
http://orcid.org/0000-0003-4136-4962
BM
Weinstein
Oncogenesis and Development Section, Zebrafish Core.
Raman
R
Sood
Oncogenesis and Development Section.
P Paul
http://orcid.org/0000-0002-6779-025X
PP
Liu
D000818:Animals; D023081:CCAAT-Binding Factor / Q000235:genetics* / Q000378:metabolism; D050676:Core Binding Factor Alpha 2 Subunit / Q000235:genetics* / Q000378:metabolism; D055786:Gene Knockout Techniques; D006410:Hematopoiesis / Q000502:physiology*; D006412:Hematopoietic Stem Cells / Q000378:metabolism*; D017403:In Situ Hybridization; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015027:Zebrafish; D029961:Zebrafish Proteins / Q000235:genetics* / Q000378:metabolism
D023081:CCAAT-Binding Factor; D050676:Core Binding Factor Alpha 2 Subunit; D029961:Zebrafish Proteins