Date of Award

Spring 2008

Document Type

Thesis

Degree Name

Bachelor of Science

Department

Biology

First Advisor

Dr. April L. Hill

Abstract

Sponges are considered the oldest and most basal part of the metazoan lineage and therefore possess a unique set of gene families that are highly conserved among all animals. One of these gene families is known as Sox transcription factors. Sox genes are known to play important roles in complex animals such as the specification of the primary layers of the body, determination of sex, and most recently induction of induced pluirpotent stem cells (iPS cells) from both human and mouse fibroblasts with the help of three other transcription factors. We have found that two different demosponge species Halichondria bowerbanki and Ephydatia muelleri already possess at least three distinct Sox transcription factors using evolutionary PCR and bioinformatic approaches. This supports the hypothesis that eumetazoans possessed at least three distinct Sox genes. To better understand the role that each of these Sox transcriptions may have played during the evolution and development of complex body plans we conducted both temporal and spatial expression analysis. We performed both RT-PCR and Real Time RT-PCR on all Sox genes isolated from both marine and freshwater sponges. These studies demonstrated that Sox genes are expressed during larval and adult development in marine sponges and during the development of gemmules to fully functioning adult stages in freshwater sponges. In situ hybridization studies have revealed that one of the Sox genes is expressed in developing embryos of the marine sponge. Furthermore, at least one Sox gene in both the marine and freshwater sponges shows distinct expression in archeocytes, the sponge stem cell. The presence of Sox expression in archeocytes suggests a role in cell specification or differentiation, as well as suggests a possible role in evolution of multicellularity. Therefore this study provides an establishment for future studies aimed at testing the hypothesis that the Sox transcription factor family had a crucial role in the evolution of animal multicellularity.

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