Homeobox genes in the Ctenophora: identification of paired-type and Hox homologues in the atentaculate ctenophore, Beroë ovata.

Homeobox-containing genes are a phylogenetically widespread family of transcription factors that can regulate cell fates during embryogenesis. Two distinct homeobox gene sequences are described for the atentaculate ctenophore Beroë, the first homeoboxes to be identified in this phylum. Beroë homeobox fragments were cloned in a survey of genomic DNA using polymerase chain reaction (PCR). Parsimony, neighbor-joining, and maximum likelihood methods were used to infer the orthology of the ctenophore sequences to specific homeoboxes from higher metazoans including Drosophila, Caenorhabditis elegans, and humans. Cteno-paired appears most closely related to paired-typed homeoboxes. This is the first evidence of a paired-type homeobox in one of the so-called diploblastic animals. Cteno-Hoxl appears most closely related to members of the Hox class, particularly Antennapedia.