Evolutionary history of the Snail/Scratch superfamily.

The Snail transcription factors have crucial roles in metazoan development and disease. A phylogenetic analysis from placozoans to humans confirms that, along with the Scratch genes, Snail genes constitute a subgroup of the C(2)H(2) zinc-finger transcription factors, within which neither the SNAG domain nor the number of fingers define group identities. Independent duplications in the different metazoan groups gave rise to the current complement of Snail genes, and the origin of the Snail/Scratch family can be traced back to a protosnail gene that underwent tandem duplication in the last common ancestor of Diploblasts and Bilateria.