Figure 2.

(a) Phylogenetic relations of the amphioxus FoxD gene and the five vertebrate FoxD genes that arose from whole-genome and gene duplications. (b) AmphiFoxD is expressed in the forebrain, somites and notochord. In vertebrates, the ancestral FoxD expression domains have been partitioned among four of the five duplicates, FoxD1, FoxD2, FoxD4 and FoxD5. FoxD3 has acquired a new domain in neural crest. Experimental evidence has shown that FoxD3 acquired both new regulatory elements and a new amino terminal sequence, both of which are essential for its role in neural crest [45,46].