Fig. 6. Regulation of Nodal expression by chick Cer. (A-C') Effect of chick Cer (cCer) overexpression. Chick embryos were electroporated with pCAGGS-cCerCDS (coding sequence) on the left (A-B') or right (C,C') side at Hamburger and Hamilton stage 4 (HH4) and fixed at HH8. pCAGGS-RFP was electroporated alone (control; A,A') or with pCAGGS-cCerCDS (B-C'). (A-C) Nodal transcripts detected by whole-mount in situ hybridization. (A',B',C') Merge of bright-field and RFP fluorescence images. cCer overexpression on the left side suppressed Nodal expression (A) in the left lateral plate mesoderm (B; arrow in A), whereas cCer misexpression on the right side had no effect (C; arrow). Nodal transcripts were always detected in the node (A-C; arrowheads). (D-F') Effect of cCer knockdown. HH4-6 chick embryos were electroporated on the left side with fluorescein-tagged morpholinos (MO) and fixed at HH8-11. (D-F) Nodal transcripts detected by whole-mount in situ hybridization. (D',E',F') Merge of bright-field and fluorescein green fluorescence images. (E,F) Nodal expression was ectopically induced by cCer MO in the right lateral plate mesoderm (black arrows), whereas it was normal in the left side (white arrows). Electroporation of a control morpholino (CoMo) did not perturb Nodal left-side expression (D; white arrow). cCer, chick Cer; cCerCDS, chick Cer coding sequence.