<i>pdgfrβ2</i> expression in the developing zebrafish.

<p><i>In situ</i> hybridization of embryos at 20 hpf (A) and 24 hpf (B) using an anti-sense probe against <i>fli1a</i> or <i>pdgfrβ2</i>. <i>pdgfrβ2</i> was expressed in the floorplate (arrow) and the hypochord (arrowhead) at 20 hpf. <i>fli1a</i> is known to be expressed in the tail vasculature. Floorplate expression of <i>pdgfrβ2</i> diminished by 24 hpf while expression in the hypochord persisted and spread ventrally in association with the dorsal aorta and posterior cardinal vein (B). Cross section analysis further indicated <i>pdgfrβ2</i> expression in the hypochord (arrowhead), floorplate (arrow) and ventral somite boundary (brackets). <i>cloche</i> mutant embryos showed normal expression of <i>pdgfrβ2</i> indicating that <i>pdgfrβ2</i> was not expressed in endothelial cells of the dorsal aorta or posterior cardinal vein (D). Transmission electron micrograph images of a longitudinal section through the ISVs (E). Mural cells surrounding the endothelial cells of the ISVs were absent at 72 hpf. Notochord (nc), blood cell (BC).