Manipulating Wnt Signaling during Mid-Somite Stages Disrupts the Laterality of Nodal Pathway Expression in Both LPM and Brain (A, H, K, and N) Graphs illustrate the percentage of embryos with wild-type (WT) left, reversed (rev) right, bilateral (bil), or not visible (nv) Nodal pathway gene expression (see also Tables S2 and S3). (A) Zebrafish embryos were treated with lithium chloride (LiCl) at the stages indicated and analyzed for Nodal pathway gene expression in the brain (and LPM in [H]) at 24s stage (see also Experimental Procedures). (B–G) Dorsal views of the (B, D, and F) brain and (C, E, and G) trunk LPM of 24s stage wild-type and mbl embryos, with anterior to the left analyzed for pitx2 expression. The arrows indicate the sites of pitx2 expression (epithalamus in [B], [D], and [F]; LPM in [C], [E], and [G]). (B–E) LiCl treatment of embryos at 80% epiboly results in the loss of pitx2 asymmetry in the brain alone, whereas (F–H) treatments at 14 somite stage result in disruption of expression concordantly in brain and LPM. (I, J, L, and M) Dorsal views of medaka embryos (anterior to the top, stages are indicated at the bottom left of each panel) showing (I and J) lft expression in the epithalamus and (L and M) spw expression in the LPM. Heat shock treatments were performed at 4s stage (I and J) and at 2s stage (L and M). Heat shock activation of (J and M) wnt1 in Tg(HS:GFP, HS:wnt1) transgenic medaka embryos causes bilateral Nodal pathway gene expression in the CNS and LPM (K and N). (K and N) Heat shock of wild-type embryos had no effect on lft or spw expression.
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