Fig. 7. Summary. Regionalisation of the diencephalon. At mid-somitogenesis stages, Otx1l/2 mark the presumptive ZLI (p-ZLI, light blue) and the thalamic anlage (Th, yellow), whereas irx1b is expressed only in the thalamic anlage. Shh marks the floor plate and basal plate (red) and starts to be induced in the Otx1l/2-positive pZLI (green arrows). At pharyngula stages, shh is expressed in the mature ZLI (red) and the territory of the Shh-positive ZLI is restricted by the thalamic expression of irx1b (red T-brackets).