Fig. 4. Induction of Nodal and Lefty1 by transplanted left LPM. (A) Schematic representation of the tissue transplantation system. (B-K) Expression of Nodal (N in B) and Nodal plus Lefty1 (N+L1 in C-K) was examined by whole-mount in situ hybridization 3 hours after the indicated type of transplantation. Genotypes of the recipients and donors are shown in red and blue, respectively, at the top of each panel. Donor tissue was derived from left LPM of the indicated embryos. The transplant sites in the host embryos are indicated by square brackets (B,C,E-K). Donor tissue was transplanted to the anterior region of LPM in host embryos, with the exception of the embryo shown in H,J, which received the transplant in the paraxial mesoderm (IPAM). Two representative Foxh1^c/- embryos that received a transplant derived from the left LPM of wild-type (WT) embryo are shown in F,G. Endogenous Nodal expression in the transplant is detectable in G but undetectable in F. Transverse sections at the planes indicated in C are shown in D and E; black and white arrowheads indicate left and right PFP, respectively. (J,K) Magnified views of the regions boxed in H,I, respectively. Arrowheads in J,K indicate Lefty1 expression induced in left PFP.