Figure 3.

Snail2 and Sox3 Behave as Mutual Transcriptional Repressors in the Chick Embryo

(A–E) Control embryo electroporated with a vector encoding GFP (A) shows the normal pattern of Sox3 expression in a dorsal view (B) and in a transverse section (C). (D) and (E) are high power images of the areas demarcated in (C).

(F–K) Similar images taken from an embryo electroporated with Snail2 in the anterior epiblast shows the repression of Sox3 expression in the electroporated region (arrow in H and sections in I). High power images comparing the electroporated with the control side confirm Sox3 downregulation (J and K).

(L–Q) Electroporation of a dominant-negative form of Snail2 (DN-Snail2) in the primitive streak extended Sox3 expression to the embryonic midline (arrow in N), as better assessed in the images shown in (O–Q).

(R–X) Ectopic Sox3 expression by electroporation at the primitive streak inhibited Snail2 expression (black arrow in T and a section at different magnifications in (U–X).