Fig. 7. Nv-snailA and NvsnailB. Phylogenetic analysis and gene expression. (A) Alignment of 105 amino acids containing repeated C₂H₂ zinc-finger motifs. (B) Phylogeny of snail sequences. The tree was constructed and labeled as in Fig. 3. Sequences included in the analysis are: escargot, Drosophila, residues 344-446; Kruppel, Drosophila, residues 250-354; Kruppel-like protein (zinc finger protein 443), Homo, residues 449-477 plus 505-580; scratch, Drosophila, 498-600; scratch1, Homo, 222-324; snail, Drosophila, residues 280-383; snail, Podocoryne, residues 226-238; snail 1, Homo, residues 154-257; snail 2, Homo, residues 159-261; snail A, Nematostella, residues 156-258; snail B, Nematostella, residues 154-256. The tree is drawn as though rooted using the Kruppel clade as an outgroup. (C-J) Expression of Nv-snailA through development. (C) Nv-snailA transcript is not detectable at early cleavage stages. (D) Expression becomes visible in the late blastula at the site of the blastopore. (E) The embryo initiates gastrulation at the site of Nv-snailA expression. (F) The first cells that invaginate into the blastocoel express Nv-snailA. (G) Expression continues throughout the process of gastrulation as cells move in to the blastocoel. (H-J) All of the cells of the gastrodermis, but none of the cells of the epidermis express Nv-snailA up through the polyp stages. The asterisk indicates the site of the mouth. The expression of Nv-snailB is indistinguishable from Nv-snailA. Arrows in G,H,J indicate endoderm.