Zeb2 is not essential for the formation of hematopoietic clusters in the AGM. (A) Quantification (right panel) of intraaortic hematopoietic clusters budding from the hemogenic endothelium by whole-mount CD31/cKit immunofluorescence staining of AGM region of E11.5 control wild-type and Zeb2^{−/ΔTie2-Cre} embryos (400× magnification) Bars represent mean ± SD.(B) Hematoxylin/eosin staining (200× magnification on the left, 600× magnification on the right), X-gal staining for LacZ expression showing Cre excision in budding hematopoietic clusters from excised ROSA26-LacZ allele (arrows in B) and (C) IHC with a Zeb2 antibody on AGM sections of E10.5 Zeb2^{−/ΔTie2-Cre} embryo (200× magnification on the left, 600× magnification on the right) showing lack of Zeb2 immunoreactivity in the budding hematopoietic clusters (arrows). (D) Vav-iCre–mediated loss of Zeb2 recapitulates the Zeb2^{−/ΔTie2-Cre} cephalic bleeding phenotype. Zeb2^{−/ΔVav-iCre} mice die around birth and show massive cerebral bleeding (arrow).