Fig. 6. (A-D) Expression of Snail in the embryonic chick limb at stages 25 (A), 26 (B), 29 (C), and 31 (D). Note the progressive increased labeling of the interdigital regions at stage 31 (D) in correlation with the establishment of INZs. (E) Expression of Snail in the duck leg autopod at day 9.5 of incubation. Note that the interdigital domains of Snail become restricted distally coincidently with the zones of interdigital cell death in the duck (compare with Fig. 3E). (F) Upregulation of Snail in the third interdigit of the duck leg 14 hours after implantation of a FGF-bead (*). (G) Duck leg bud 14 hours after implantation of a FGF-bead (white asterisk) and a Noggin-bead (black asterisk). Note that the positive effect of FGFs on Snail expression is inhibited in the zone of influence of the Noggin-bead. (H) Upregulation of Snail, 6 hours after implantation of a BMP-bead (*) into the third interdigit of the chick. (I) Down-regulation of Snail expression 6 hours after implantation of a Noggin-bead (*) into the third interdigit of a stage 28 chick embryo. (J) Upregulation of Snail in the chick 10 hours after interdigital implantation of a FGF-bead (*) at stage 28. Note that the upregulation of Snail parallels that observed for BMPs (see Fig. 4B). (K) Down-regulation of Snail, 24 hours after interdigital implantation of a bead (*) incubated in SU5402. (L) Expression of Snail in the chick interdigit 8 hours after implantation of a BMP-bead (white asterisk) 24 hours after implantation of a SU5402 bead (black asterisk). Note that in these conditions BMPs are unable to upregulate Snail expression (compare with H and K).
