Evolution of a conserved gene regulatory network among echinoderms: A comparison of genes expressed in the skeletogenetic lineage of the ophuroid Ophiocoma wendtii and the echinoid Strongylocentrotus purpuratus

One of the most fundamental and critical functions of embryological development is the control and regulation of differential genes and gene networks. The study of the gene networks involved in development is a mechanism for understanding the developmental process at its most basic level. An evolutionary change in a morphological feature or features must depend on a reorganization or co-option of one or more developmental gene regulatory network just as retention of an ancestral morphological trait must rely on retention of a common gene regulatory network. Studying two closely related classes in the same phylum with the same essential morphological feature yet with unique developmental characteristics provides insight into the evolution of these evolutionarily resolute gene regulatory networks. We have developed a new model system using brittle stars to further these studies. In this investigation I have identified key genes of the gene regulatory network (GRN) found in embryonic endo-mesoderm development in the sea urchin, responsible for embryonic skeletogenesis, and compared these key genes with homologues in the brittle star. From the examination of two closely related gene regulatory networks found in two related classes of Echinoderms insight can be gained into the foundation of morphological change over time