Figure 1
From: Wnt3 and Wnt3a are required for induction of the mid-diencephalic organizer in the caudal forebrain
Canonical Wnt signaling is required for induction of Shh expression in the MDO. MD organizer in lateral views of embryos with anterior to the left at 28 hpf. Blockage of canonical Wnt signaling by treatment of embryos with 40 μM IWR1 at different time points leads to the following alterations in the formation of the shh positive MDO: 10 to 28 hpf - strong decrease (B, arrow), 12 to 28 hpf - mild decrease (C) 14 to 28 hpf - no alteration (D). Shh expression at the MDO is unaltered if Dkk1-GFP positive cells are located in the telencephalon and the pretectum (E), however, the shh positive MDO is absent if Dkk1-GFP cells are located in the thalamic complex (F, n = 6/10, arrow). Ectopic activation of the Wnt signaling pathway by BIO treatment (G, n = 12/18), in the axin1-/- mutant embryos (H) as well as embryos with an implanted Wnt3a loaded bead (I, J, n = 3/5) leads to a increase of MD organizer shown by expanded shh expression (black arrows).