Fig. 4.

Ectopic expression of Sox6. (A) Schematic illustration of the two isoforms of chick Sox6 with a myc-epitope tag (gray) at the C terminus. (Lower) The blue box represents a 60-base-long exon found in isoform 2. (B–G) Chicken embryos at HH stage 14–16 were used for transfection by electroporation. Expression was confirmed by immunostaining for the myc epitope (B and E). Embryos were harvested 24 h later, and RNA in situ hybridization and immunostaining were carried out to examine the expression of Sox2 and Isl1/2, respectively. Forced expression of Sox6 led to up-regulation of Sox2 (C and F) and down-regulation of Isl1/2 (D and G). Serial sections at the forelimb level were used.