Figure 6

XDab2 acts as a specific mediator of activin-like signaling for VEGF gene induction. (A and B) Depletion of XDab2 inhibits the induction by activin-like signal of late mesodermal target genes such as VEGF and muscle actin (MA) without affecting that of early mesodermal (Chordin, Xbra and Mix2) and late endodermal (Sox17 and Endodermin) target genes in animal caps. (C) XDab2 enhances the activity of activin protein to induce VEGF, but the expression of other target genes was not changed by XDab2 overexpression. (A-C) Four-cell stage embryos were injected into the animal pole region with a combination of the indicated reagents and the animal caps isolated at stage 8 were cultured to stage 10.5 (B) or 20 (A and C) and then subjected to RT-PCR analysis. The amount of the injected reagents: 2 ng, CA hALK4 RNA; 40 ng, Co MO; 40 ng, XDab2 MO; 2 ng, XDab2 RNA. In panel (C), the animal caps were cultured in the presence of 5 ng/ml of activin protein. +RT and -RT; control RT-PCR on the whole embryo RNA in the presence or absence of reverse transcriptase. AC, uninjected animal cap cells.