Meeting Abstract
Hox genes are Homeobox transcription factors that are responsible for patterning along the primary axis and are found in all bilaterians, a group that makes up 99% of metazoan life. Cnidarians, such as anemones and corals, represent the only phylum outside of the Bilateria to have Hox genes, making them an important sister group for studying Hox gene evolution. The anthozoan gene Ax6a is a cnidarian specific Hox gene that has maternal expression and is expressed at the site of gastrulation, suggesting it has an important role in early development. Furthermore, Ax6a is asymmetrically expressed along the future site of gastrulation when visualized with in situ hybridization. When Ax6a is prevented from being expressed through the injection of eggs with an Ax6a antisense Morpholino, treated embryos fail to gastrulate and oral, aboral, and directive axis patterning is disrupted, suggesting that it has a large effect on the embryo’s development outside of its own asymmetrical oral domain. Furthermore, when Ax6a mRNA is injected ectopically into random blastomeres at the 8-32 cell stage, a second site of invagination, and later, gastrulation is induced, with expression of some markers for oral development. This implies that Ax6a plays a very important role in axial patterning and suggests that anterior Hox genes may have had fundamental roles in establishing the primary body axis in the bilateral lineage.
