Dr. Martin will examine the development and differentiation of undifferentiated cells, interstitial cells, during embryogenesis in a marine hydrozoan, Halocordyl disticha. Hydrozoan planulae contain a population of interstitial cells which either divide to maintain the I- cell population or differentiate into ganglionic nerve cells or nematocytes. Embryos treated with colchicine or hydroxyurea have either no or reduced numbers of I cells respectively. Five major aspects of I- cell behaviour in larval tissues will be analyzed: 1) the dynamics of larval stem cell repopulation in epithelial planulae; 2) the involvement of I-cells and their derivatives in metamorphosis; 3) a determination if larval I-cells exhibit restrictions in their developmental potential with time; 4) an examination of the stem cell properties and developmental potential of a larval population of hydroxyurea resistant interstitial cells; and 5) a comparison of the larval I-cell population to the adult I-cell population. Pieces of different treated or aged control embryos will be grafted to epithelial planulae and removed at various times after grafting for analysis. The general problem approached by this research is how the spatial pattern of differentiated cells is established during embryogenesis and how such an organization is carried over and maintained in the adult state. Dr. Martin is studying cellular commitment, proliferation and differentiation of a manipulatable population of stem cells in a marine hydrozoan as a model.
