Fig 7.

Evolutionary history and schematic representation of the distribution of functional enhancers for Snail and Slug expression in the lens (blue), pnc (red), and tail bud mesenchyme (green) across vertebrate species. Xenopus Slug (light red) is expressed in pnc but at a later stage than Snail (45); Snail is the gene expressed in the tail bud (R. Mayor, personal communication). Amphioxus is shown as an outgroup and is considered to be the ancestral condition before Snail duplication; squares and circles denote enhancers driving expression to the lens, the dorsal neural tube, and the tail bud.