Dr. Danielle de Jong is a new post-doctoral research fellow at Kewalo Marine Lab, working with Dr. Elaine Seaver. Dr. de Jong completed her Ph.D. on nervous system patterning genes in the coral Acropora millepora with Dr. David Miller at James Cook University in Townsville, Australia. Following an Alexander von Humboldt Post-Doctoral Fellowship with Dr. Bernd Schierwater working on the basal metazoan Tricoplax adhaerens, Dr. de Jong has joined the Seaver Lab to study mechanisms of regeneration using the polychaete annelid Capitella teleta. Specifically, she is interested in understanding how this marine worm regenerates its segments following amputation.
Regeneration is a very active field of study as understanding the molecular mechanisms of regeneration in various animal models potentially opens up many possibilities in the practice of regenerative medicine. The ability to regenerate tissues is present in many animal phyla to some degree. Yet exactly what mechanisms are involved, and why some animals are able to regenerate while others cannot, remains poorly understood.
"Where studied in model vertebrate and invertebrate systems, it has been shown that animals exhibit significant diversity in how they regenerate," notes Dr. de Jong. "So, studying organisms from many different phyla is extremely important in order to fully understand the evolution of regeneration, and add to our growing knowledge of how different systems are utilized in diverse animals".
Annelids, or segmented worms, are an excellent group in which to study regeneration. In general, they exhibit robust regenerative abilities following complete transverse amputation along the body. This provides an opportunity to study qualitative and quantitative variation in regenerative abilities within a group of closely related animals.
Previous work on regeneration following transverse amputation in Capitella has been limited to general observations of changes in morphology and gene expression, including a characterization of the well-conserved germ cell gene piwi. However, regeneration in Capitella has not been characterized in detail at the molecular and cellular level, which is just what Dr. de Jong intends to do.
"For my research, I'll be initiating a more in-depth analysis of regeneration in Capitella early juveniles, approximately 2 weeks following metamorphosis from a swimming larva," explains Dr. de Jong. "This will initially involve basic observations on the re-formation of various structures and tissues and body re-patterning over time using techniques of antibody and RNA in situ hybridization staining".
As a first step, this work will help to elucidate the genes and molecular networks involved in rebuilding a body region following amputation. Another important question that needs to be addressed is the origin of the new tissue. Where does the tissue for the regenerating segments come from? There are two possible sources for the new segments – either from existing tissue, through mechanisms of dedifferentiation or transdifferentiation of cells, or from a group of resident 'stem-cells' within the animal, which migrate to the site of the wound and proliferate to provide additional cells with which to re-build the body.
"In order to begin to answer some of these questions, I am attempting to track cells and their movements within regenerating animals by labelling specific precursor cells with DiI, a fluorescent dye, in the early embryo and following these through to the juvenile stages", says Dr. de Jong.
In addition to labelling precursor cells, Dr. de Jong would also like to label specific cells by injecting DNA constructs containing short regions of DNA that control gene expression (promoter fragments) linked to a fluorescent reporter protein (e.g.., GFP) into developing worm embryos. These types of experiments will allow her decipher if particular genes, such as the germ cell markers piwi, vasa, and nanos, are involved in the wound healing and regeneration response and whether this mechanism involves actual cell migration, or just 'switching on' these genes in the regenerating tissue.
Dr. de Jong's research background is diverse - including work on corals, Trichoplax, and vertebrate heart development - but her true interests lie in evolutionary developmental biology, which is what led her here to Kewalo Marine Lab.
"While I appreciated the opportunity to learn about the field of medical genetics and vertebrate model systems, what I realized was that my real passion is in trying to answer basic questions about how animals have evolved. What is it that makes each animal different, and what broad similarities exist which can help us understand what the first multicellular animal may have looked like?"
"I am extremely lucky to be able to follow these questions in beautiful Hawaii in such a supportive and happy environment as Kewalo Marine Lab, and look forward to making some significant inroads in the field of regenerative biology".