Fig. 6. Flt-1 and flk-1 induction in the skin of transgenic mice. In situ hybridization analysis for flt-1 and flk-1 in the skin of 15.5 d.p.c. embryos. The mRNA for flt-1 transmembrane receptor is undetectable in the skin of wild-type embryos (A,B) and is induced in the dermal endothelium of transgenic embryos (C,D). Flk-1 is transcribed in the skin endothelium of wildtype mice (E,F) and consistently upregulated in the dermal endothelium of transgenic embryos (G,H). (A,C,E,G) Bright field; (B,D,F,H) dark field. Bars, 40 µm. RNase protection assay for flt-1 (I) and flk-1 (J) confirmed that mRNA levels for both receptor are increased in the skin of transgenic 15.5 d.p.c. embryos compared with wild-type controls.