Fig. 4.

The Gata2-3 enhancer targets the hemogenic aortic endothelium and requires Ets sites for its in vivo activity. (A) Transgenic lacZ reporter constructs with WT enhancer (Gata2-3) or enhancer with mutant Ets sites (mEts Gata2-3). The number of embryos showing staining in the DA (AGM region) or midbrain out of the total number of E10.5 and E11.5 F₀ transgenic embryos generated with each construct is listed alongside. (B) Representative F₀ embryos stained with X-Gal for lacZ expression. (i) Gata2-3/SV/lacZ E10.5 whole-mount showing staining in the DA (boxed). (ii) Magnified view of the boxed area in i showing concentration of the reporter along the ventral surface of the DA (arrow). (iii) Histological section corresponding to region in (ii) showing prominent endothelial staining (arrow). (iv) mEts Gata2-3/SV/lacZ E11.5 whole-mount embryo showing nonspecific staining in the region of the DA (boxed). (v) A magnified view of the boxed area in iv. (vi) Section corresponding to region in v showing absence of endothelial staining. (C) Magnified lateral view of heads of X-Gal stained F₀ embryos in B. (i) Gata2-3/SV/lacZ whole-mount embryo showing prominent lacZ expression in the posterior commissure (block arrow) and tectal neurons into the mesencephalon (arrow). (ii) mEts Gata2-3/SV/lacZ whole-mount embryo showing loss of lacZ staining. The ectopic staining in the maxillary region was seen in only one of six F₀ mutant transgenic embryos. (iii) Scl-7E3/lacZ wholemount embryo showing staining similar to that seen with the Gata2-3/SV/lacZ transgenics. D, diencephalon; ME, mesencephalon; PC, posterior commissure; T, telencephalon.