The posterior-to-anterior (PA) propagation of pitx2 and lft1 depends on spaw function. A,B: In wild-type (WT; A) pitx2 is expressed in lateral plate mesoderm (LPM; black arrow) and in Rohon-Beard cells (black arrowhead). In spaw morphants (B), pitx2 is not expressed in LPM but is expressed in Rohon-Beard cells (black arrowhead). Embryos were at 18 somite stage (SS); anterior to left. C,D: Spaw expression is normal in WT (C) and spaw morphants (D) in the peri-Kupffer's vesicle (KV) bilateral domains (green arrow). In contrast, left-sided LPM spaw expression (green arrowhead) and lft1 midline expression (blue arrow) seen in WT (C) is absent in spaw morphants (D). Embryos were 16 SS; anterior to the top.
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