Figure 3

XDab2 is required for the formation of ISV sprouts. (A) Control embryos injected with Co MO (30 ng) show no defects in the sprouting ISV. (B-E) XDab2 knockdown impedes the formation of ISV and this inhibitory effect can be rescued by coexpression of Xenopus Dab2 (D) or human Dab2 (E) RNA, which is resistant to the translational inhibition of MO. One blastomere of two-cell stage embryos was injected with XDab2 MO (30 ng) alone or with XDab2 RNA (250 pg) or hDab2 RNA (250 pg), and then embryos fixed at stage 34 were insituhybridized against Xmsr (B, D and E) or EphB4 (C). Arrows and arrowheads represent the normal and disrupted ISV, respectively. (F and G) Microangiography showing that XDab2 depletion causes abnormality in blood circulation in stage 42 embryos (F: 47%, n = 17), while Co MO-injected embryos reveal the normal circulation (G: 0%, n = 8). Arrowhead and asterisks represent the leaky vessels and the absence of ISV, respectively. DLAV, the dorsal longitudinal anastomosing vessel; DA, the dorsal aorta; PCV, the posterior cardinal veins; ISV, the intersomitic veins. (H and I) The graph and table showing the results from the loss-of-function analysis of XDab2. (J and K) Loss-of-function of XDab2 interferes with vasculogenesis. (J) The illustration of transverse section analysis. Roman numerals (I – IV) indicate the positions of embryo sections shown in panel (K). (K) A series of embryo sections show the absence or decrease of the endothelial marker, Xmsr in PCV (arrows) and VVN (arrowheads) on the XDab2 MO-injected side, which is indicated by the β-galactosidase staining. The XDab2 knockdown embryos (n = 12) with the angiogenic defects were analyzed and all of them showed these phenotypes.