Fig. S1. Electroporation of unrelated siRNA oligos does not reduce Nolz1 expression. (A-C) Confocal micrographs of sectioned St 23 electroporated chick embryonic spinal cords. GFP expression marks the electroporated half of the spinal cord. Immunohistochemical analysis shows no change in the levels of Nolz1 or Islet1/2 expression. Images are representative of at least five embryos.

Fig. S2. Nolz1 or Grg5 overexpression does not induce ectopic MNs or Hoxc6 expression. (A-D) Confocal micrographs of transverse sections and (E,F) dorsal right halves of electroporated spinal cords at St 21. The right-hand side of the spinal cord is electroporated in all cases. Dashed white line denotes lateral boundary of the spinal cord. Images are representative of at least five to ten embryos for each experiment.

Fig. S3. Lim1⁺ ectopic MNs generated by Nolz1 and Grg5 coexpression do not express Hoxc6. (A-C) Confocal micrographs of electroporated dorsal right halves of sectioned chick spinal cords at St 23/24. Triple labeling by immunohistochemistry shows Islet1/2⁺ cells that coexpress Lim1 (yellow cells marked by arrows) and do not express Hoxc6 (blue). Images are representative of at least five embryos.