Fig. 3. Expression of exogenous Scl under control of the Scl 3' enhancer rescues haematopoiesis in Scl^–/– embryos. (A) The +6E5/Scl-lacZ/3'En transgene. (B) X-gal staining of E7 embryo carrying the +6E5/Scl-lacZ/3'En transgene showing lacZ expression in the extra-embryonic mesoderm. (C-F) E8 embryos of the indicated genotype analysed by whole-mount (C, E) or cryostat sections (D,F) for lacZ staining. Note the presence of small numbers of round haematopoietic cells in blood islands of rescued yolk sacs (F). h, heart; p-sp, para-aortic splanchnopleura; ys, yolk sac; arrows, lacZ⁺ blood cells; arrowheads, lacZ⁺ endothelial cells. (G-O) E9 embryos of the indicated genotypes. Unfixed Tg^+/–Scl^–/– embryos were anaemic (compare G with J and M). Histological sections of wax-embedded X-gal-stained embryos (H,I,K,L,N,O) demonstrated the presence of haematopoietic cells in rescued embryos (K,L). Embryos are from transgenic line 2708 and were genotyped by PCR.