Fig. 4. Induced ubiquitous expression of sema3a1 adversely affects the distribution of cells expressing the angioblast marker fli1, but not the hematopoietic marker, gata1. All panels show the trunk of whole-mount embryos following in situ hybridization for fli1 (A-D) or gata1 (E-H) in wild-type embryos (A,B,E,F), yot embryos that express sema3a1 through the entire somites (C,G), and hsp70:^gfpsema3a1^myc transgenic embryos (D,H) following heat induction at 15 hpf. In wild-type embryos, fli1 is expressed diffusely between the notochord and yolk tube at 20 hpf (A), but by 25 hpf fli1 is expressed most strongly by presumptive dorsal aorta cells immediately ventral to the notochord (B, arrowhead). At 25 hpf the pattern of fli1 is disrupted with aberrant patches of cells (C, asterisk) between the notochord and yolk tube in yot embryos, and with diffused pattern in transgenic embryos following heat induction (D). fli1 expression can also be seen in the intersegmental arteries (arrows in B-D). gata1 is expressed by many cells between the notochord and yolk tube in wild-type embryos at 20 (E) and 25 hpf (F). gata1 expression is normal in yot embryos (G) and in hsp70:^gfpsema3a1^myc transgenic embryos at 25 hpf following heat induction at 15 hpf (H). Scale bar: 20 µm.