Abrogation of Mil function facilitates anterior migration of the presumptive prechordal plate. In situ hybridisation (A-H,O,P) of dlx3 (anterior border of the neural plate), hgg1 (anterior prechordal plate) and ntl (notochord) at tailbud stage, (I-L) of dlx3 and hlx1 (posterior prechordal plate) at tailbud stage, and (M,N) of spry4 (presumptive mesoderm) at 60% epiboly. (A-D) Dorso-animal views, (E-H) lateral views, (I-L) dorso-animal views and (M-P) dorsal views of wild-type (WT) embryos (A,E,I,M), WT embryos injected with 4.3 ng mil-MO (B,F,J,N), slb embryos (C,G,K,O) and slb embryos injected with 4.3 ng mil-MO (D,H,L,P). In mil-MO-injected embryos, anterior migration of the presumptive prechordal plate was promoted (B,F), as compared to WT (A,E), with regards to relative positions of the prechordal plate in relation to the anterior border of the neural plate (A-D), and to angles between the prechordal plate and the tailbud, indicated by arrowheads (E-H). Injection of mil-MO rescued the reduced migration of the anterior prechordal plate in the slb embryo (C,D,G,H), but did not alter the wider notochord (O,P, indicated by asterisks). By contrast, the altered position of the posterior prechordal plate correlated with that of the anterior prechordal plate (K,L). (M,N) The enhancement of migration was not observed in the lateral mesoderm (brackets), but was specific to the prospective prechordal plate (arrow).