Meeting Abstract

P3.23  Saturday, Jan. 5  Early diversification of the T-box gene family in the poriferan lineage HOLSTIEN, K.**; HILL, M.S.; HILL, A.L.; University of Richmond, VA; Univerisity of Richmond, VA; University of Richmond, VA ahill2@richmond.edu

The T-box family of transcription factors is involved in a variety of important developmental processes in all members of the Metazoa. These genes play vital roles in specification of morphological structures derived from all three germ layers. T-box genes appear to be restricted to the Metazoa given that they have not been reported in plants, fungi or protists. However, T-box family members have been identified in all of the extant basal metazoans including sponges, cnidarians, ctenophores, and placozoans. Our analysis of the T-box constituency in poriferan genomes supports a recent hypothesis that the common ancestor of the Eumetazoa already had a complex complement of T-box genes. Previous studies in sponges have reported at most two T-box genes present in a given sponge genome (including isoforms of one Brachyury class gene). Our surveys of the Amphimedon queenslandica genome as well as PCR-based screening of two other demosponge genomes (Halichondria bowerbanki and Ephydatia muelleri) indicate that there are at least five different T-box family members present in some sponge genomes. Several of these gene families appear to be unique to the Porifera and a duplication event may have occurred exclusively within the poriferan lineage for one Tbx family. In situ hybridization analysis in Halichondria larvae for two of the T-box genes indicates distinct patterns of expression that may suggest possible roles in development.