Figure 2.

The mid-diencephalic organizer (MDO) is the source for members of three morphogen signaling families in the ZLI of the embryonic vertebrate brain. Expression of Wnt signaling molecules [(A), green] overlaps with Shh producing cells of the MDO [(B), red], whereas expression of members of the Fgf family [(C), blue] is located in the prethalamus and overlaps partially with the Wnt signaling source in the dorsal roof plate. Taken together, these three families of signaling molecules encircle the developing thalamus from dorsal (Wnt and Fgf), ventral (Shh) and rostral (Wnt, Shh, and Fgf). Th, thalamus; PTh, prethalamus; HTh, Hypothalamus; Eth, epithalamus; Tel, Telencephalon; Ptec, pretectum; Mb, midbrain; MDO, mid-diencephalic organizer.