Fig. 6

Pipefish Pitx1, a vertebrate protein important for hindlimb and tooth development, contains several homopolymeric expansions. Shown are well-aligned regions of Pitx proteins across several vertebrate species, starting from the last five amino acids of the homeodomain (shaded gray). Poly-alanine and poly-proline expansions (shown in red) in pipefish Pitx1 and Pitx3 between the homoedomain and the OAR domain (shaded turquoise) are not found in the Pitx proteins of other compared fish; however, there is a poly-alanine expansion at a different location in human Pitx3. One of the Pitx1 polyalanine expansions is shared with the messmate pipefish (Corythoichthys haematopterus), a distantly related syngnathid [11], and none are present in the robust ghost pipefish (Solenostomus cyanopterus), a member of a close, pelvic-fin-bearing outgroup to the syngnathids [72, 73]. Gulf pipefish also has a single amino acid insertion (also shown in red) in the conserved OAR domain