Fig. 1. Expression of Nodal and Pitx2 in the left lateral plate mesoderm is dependent on BMP. Ventral views of stained embryos at HH stage 7 (A-C), or HH stage 8 (D-P). (H) A transverse section through the embryos shown in G. The plane of sectioning is indicated. Normal control embryos in A-E were hybridized with a probe for Nodal. The number of somites is given in the bottom right-hand corner in A-E. All other embryos were placed in New culture and implanted with BMP2-expressing cells (F,G,L,M), control cells (I,K,N,P), or with Noggin-expressing cells (J,O). Cell aggregates were placed in the lateral plate mesoderm at HH stages 4 (F), 5 (G,I-L,N-P) or 6 (M). The embryos were cultured until four somites had formed and subjected to whole-mount in situ hybridization with probes for Nodal (A-K) and Pitx2 (L-P). Green arrowheads indicate the tongue-like expression domain of Nodal that connect the paraxial and LPM expression domains in D,E. Red arrowheads indicate ectopic or loss-of expression as a result of the manipulation. Asterisk marks the implanted cell aggregate.