Fig. 2

prox1b embryonic expression pattern analyzed by in-situ hybridization.

(A) the first prox1b signal appears at 10 somite (s) stage in the central nervous system (CNS) (black arrowhead). (B) at 24hpf and (C) 36 hpf prox1b expression continues to be restricted to the CNS of the embryos (black arrowheads). (D) at 48 hpf prox1b mRNA is still detectable in the CNS, and is now expressed in the posterior cardinal vein (PCV) and the sprouts emanating from this vessel into the intersegmental space (black box). (E) magnification of the region boxed in D; PCV (blue arrowhead) and vein sprouts (black arrowheads) are indicated. (F) cross sections of 48 hpf-prox1b-hybridized embryos. (F, bottom) prox1b is expressed in the endothelial cells of the vein wall (blue arrowhead), and not in the dorsal aorta (DA) (red arrowhead). (F, top) prox1b signal is also visible on both sides of the trunk (black arrowhead), adjacent to the notochord (n). (G) at 72 hpf prox1b expression pattern is comparable to the 48 hpf stage, being the signal detectable in the CNS (black arrowhead), in the PCV and the sprouts emanating from the PCV (black box). (H) magnification of the region boxed in G; PCV (blue arrowhead) and vein sprouts (black arrowheads) are indicated. (I) cross section of a 72 hpf-prox1b-hybridized embryo. The endothelial cells of the PCV are still labeled (blue arrowhead), while the signal is completely absent from the DA territory (red arrowhead). prox1b is now expressed in the space comprised between the DA and the PCV (arrow), where the TD forms starting from around 72 hpf. y, yolk. Scale bars represent 100 μm (A,B,C,D,G) or 20 μm (E,F,H,I).