Meeting Abstract
Hox genes are a group of transcription factors known to be important in patterning the primary body axis of most animals during development. Unlike other animals, the echinoderm body plan incorporates a pentaradial adult form built upon a bilateral larval plan. It has long been suspected that changes in the presence/absence, arrangement, and expression of Hox genes in stem ancestors of echinoderms have contributed to their unique adult body plan. Although the genome of Strongylocentrotus pupuratus has been fully sequenced and studied extensively, genomic information from other echinoderms remains scarce. We have sequenced and assembled the genomes of three echinoderm species from three of the remaining four classes: Ophionereis fasciata (brittle star), Patiriella regulars (sea star), and Australostichopus mollis (sea cucumber). In this study we characterize 361 previously unidentified homeobox genes. We report the first evidence of the presence of Hox2 in Asterozoa, which had been previously thought to be absent. The absence of Hox4 within holothuroids was also confirmed. Hox4 had previously been shown to be absent in echinoids, meaning that Hox4 was most likely lost in Echinozoa. We identified a novel family of posterior-class hox genes, Hox11/13d, in each of the three species, suggesting that this might also be present within Crinoids and Echinoids. The increased resolution of echinoderm hox genes will aid further studies of the role of Hox genes in echinoderms and shed light on the role Hox genes in echinoderm body patterning.
