Fig. 4. Tsukushi interacts with VG1. (A-C) Expression of TSKB (A), VG1 (B) and WNT8C (C) in stage XII chick embryos. PMZ (arrows); Koller's sickle (arrowhead). (D-F) Expression of TSKB (D), VG1 (E) and WNT8C (F) in stage 4 chick embryos. Hensen's node (arrowheads); the middle primitive streak (arrows) (G) Co-immunoprecipitation of TSKA-Myc-His or TSKB-Myc-His and VG1-Myc. After immunoprecipitation with nickel-chelating resins, bound VG1 was detected by immunoblotting with anti-Myc antibody. (H) Co-immunoprecipitation of TSKB-Myc-His and VG1-Myc in the presence of BMP4. (I,J) VG1 mRNA (100 pg) or VG1 mRNA (100 pg) + TSKB mRNA (400 pg) was injected into ventral vegetal blastomeres at the eight-cell stage, and embryos were developed until stage 31 and in situ hybridized with a PAX2 probe. pn, pronephore; ov, optic vesicle. (K) TSKA- or TSKB-producing cells (orange) were grafted into the lateral marginal zone (a), the area opaca (b) or the area pellucida (c) with cells expressing VG1 (purple). (L) Induction of ectopic brachyury (arrow) was observed when TSKB-producing cells were grafted together into the area pellucida (`c' in K) with VG1-expressing cells.