Proposed scenario for the evolutionary history of ADAMTS proteins. During chordate evolution a series of gene duplications resulted in six ADAMTS proteins present in the Ciona genome, while an early retrotransposition event gave rise to the "angiogenesis clade" of ADAMTS proteins. This proliferation of ADAMTS proteins did not occur in invertebrates, and there is evidence of the loss of one ADAMTS ortholog from Caenorhabditis. More recent duplications that occurred early during vertebrate evolution resulted in the paired sets of ADAMTS proteins present in the human genome. The chromosomal locations of the human ADAMTS genes are indicated in parentheses and the exon structure of each human gene is diagrammed to the right of its position in the schematic phylogenetic tree, and shown in more detail in the Additional Files.