Fig. 1. Comparison of the amino acid sequence of fish Charon with the sequences of other Cerberus/Dan family members. (A) Alignment was done with the ClustalW program. Identities in the amino acid sequence of zebrafish (z) Charon to the sequences Fugu Charon, flounder (fl) Charon, Xenopus (X) Cerberus, chick (c) Caronte, and human Cerberus-related (hCerberus) are 41%, 41%, 18%, 25%, 20%, respectively. Fugu Charon and flounder Charon are the most similar to each other (63%). (B) A radial phylogenic tree of the Cerberus/Dan family proteins. The tree was calculated according to the Expansion of the ClustalW program by DDBJ (DDBJ; http://www.ddbj.nig.ac.jp) using the amino acid sequences of the cysteine-knot domain of the proteins. Zebrafish PRDC and zebrafish Gremlin are less similar (16% and 18%, respectively) to chick Caronte than to zebrafish Charon. c, chick; X, Xenopus; z, zebrafish.