Fig. 4

Fig. 4

id genes are the essential BMP targets mediating endothelial induction.

An assay was developed to quantify the percent of transplanted cells that adopt an endothelial fate (see text for details). Control cells transplanted to the ventral margin of host embryos and heat-shocked at the 12-somite stage exhibit a small percentage contribution to endothelium (green cells, A, A’, G, empty vector N^embryos = 19, N^cells = 500), which is significantly reduced when BMP signaling is inhibited in transplanted cells (B, B’, G, empty vector +dnbmpr N^embryos=19, N^cells = 1022, p=0.006). Activation of id1 or id3 causes a significantly larger percentage of transplanted cells to adopt an endothelial fate (C, C’, E, E’, G, id1 N^embryos = 16, N^cells = 1159, p<0.0001, id3 N^embryos = 18, N^cells = 574, p<0.0001), and this effect is unchanged in cells that also lack BMP signaling (D, D’, F, F’, G, id1 +dnbmpr N^embryos=16, N^cells = 614, p<0.0001, id3 +dnbmpr N^embryos=12, N^cells = 531, p<0.0001). Cell fate quantification from these experiments is represented in panel G. A stable HS:id3 transgenic line heat-shocked at the 12-somite stage and fixed 5 hr later exhibits a large expansion of the endothelial marker etv2 (I, I’) compared to heat-shocked wild-type embryos (H, H’).