Figure 7. Two FGFRL-Wnt circuits control AP patterning in planarians.
(A) Expression domains of all identified mRGs along the planarian AP axis. Wnt pathway (purple), FGFRL (orange), and Hox genes (green). In bold, genes shown here to be involved in maintaining regional identity. (B) Cartoons summarize the characterized RNAi phenotypes. ndl-3 and wntP-2 restrict the number of pharynges and mouths in the trunk region. wntP-2 RNAi animals with ectopic pharynges/mouths have an expanded ndl-3 domain whereas ndl-3 RNAi animals with ectopic pharynges/mouths have a reduced wntP-2 expression domain. fz5/8–4, ndk, and wntA restrict the brain tissue to the head. Inhibition of these genes results in ectopic posterior eyes, brain expansion, and expanded domains of head mRGs. (C) Expression domains of the two FGFRL-Wnt circuits are shown. Black brackets indicate the region controlled by the FGFRL-Wnt circuits.