Fig. 1. XMeis3-expressing cells juxtaposed to neuralized tissue induce elongation in a non-autonomous manner. (A) Schematic drawing of recombinant explant strategy. In this system, a pigmented animal cap (AC) explant taken from an embryo ectopically expressing XMeis3-encoding RNA is recombined with an albino AC taken from an embryo ectopically expressing BMP-DNR-encoding RNA. Uninjected pigmented AC explants were recombined with uninjected albino AC explants (B) or with albino explants from embryos injected with BMP-DNR-encoding RNA (0.2-0.4 ng per embryo) (C). Pigmented AC explants expressing XMeis3-encoding RNA (0.8-1.0 ng per embryo) were recombined with uninjected AC explants (D) or with explants expressing BMP-DNR-encoding RNA (E). AC explants were removed from blastula embryos (stage 8-9), recombined and cultured until late neurula (stages 18-19).