 (A) SOX3 over-expression experiments in chicken spinal cord at E4. 48 hrs post electroporation, transfected side showed decreased expression of FGFR2, NFIA and Fgfr3. Bar: 50µm. (B) 24 hrs after miss-expression of a dominant negative version of SOXB1 (dnSOXB1), premature expression of FGFR2, NFIA and Fgfr3 were found in the transfected side. Bar: 40µm. (C) 24 hrs after SOX9 over-expression in chicken spinal cord (at E4), increased expression of FGFR2, NFIA and Fgfr3 was shown compared to the un-transfected control side. Bar: 40µm. (D) Sox3 and Sox9 co-electroporation in chicken spinal cord at E4 could rescue the effect of SOX9 overexpression and FGFR2, NFIA and Fgfr3 levels were comparable to the un-transfected control side. Embryos were analyzed 24 hrs post electroporation. Bar: 40µm. (E  