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Fig. 4. Wnt-9a activates h-catenin in AV canals and causes axis duplications in Xenopus embryos. (A) AV canal explants infected with RCAS Wnt-9a activate
the h-catenin responsive TOPFLASH reporter but not the FOPFLASH reporter containing mutated TCF binding sites. Infection of AV canal explants with
RCAS control virus does not activate the TOPFLASH or FOPFLASH reporter. (B) Wnt-9a mRNA (50 pg) injected into a ventral blastomere of four-cell
Xenopus embryos causes duplication of the embryonic axis. Co-injecting 50 pg of Wnt-9a with 200 pg (C) or 500 pg (D) of Wnt-9aD288 rescues axis
duplications. Injection of 50 pg of XWnt-8 also results in axis duplications (E) that are not rescued with co-injection with 200 pg of Wnt-9aD288 (F). Coinjection
of Xwnt-8 with 500 pg of Wnt-9aD288 partially rescues XWnt-8-induced twinning as two cement glands are still evident (G). Uninjected embryos
showing Xnot-1 expression in the mesoderm overlying the dorsal blastopore lip (H). Stage 11 embryos injected with 50 pg of Wnt-9a mRNA show ectopic
Xnot-1 expression consistent with secondary axis formation (I). This ectopic Xnot-1 expression is no longer detected in embryos co-injected with Wnt-9a (50
pg) and Wnt-9aD288 (500 pg) (J). Uninjected control embryos at stage 15 undergoing normal gastrulation (K). Ventral injection of XWnt-5a inhibits convergent
extension creating gastrulation defects (L). These gastrulation defects caused by XWnt-5a injections are not rescued by co-injection with 500 pg of Wnt-9aD288
(M). Abbreviation: C = cement gland. |
