Biology Project Abstract
CELL ADHESION IN DICTYOSTELIUM DISCOIDEUM MUTANTS
Presenter:
Joanne M. Mathews, Illinois Mathematics and Science Academy, 1500 West Sullivan Road, Aurora, IL, 60506; jmathews@imsa.edu
Mentors:
Dr. Rex L. Chisholm, Northwestern University Medical School , Dept. of Cell & Molecular Biology Ward # 11-100, 303 E. Chicago Ave. , Chicago, IL, 60611; 312-503-4151; 312-503-5994; r-chisholm@northwestern.edu
Ms. Petra Fey, Dept.of Cell & Molecular Biology Ward # 11-100, Northwestern University Medical School , 303 E. Chicago Ave. , Chicago, IL, 60611; 312-503-4169; pfey@northwestern.edu
Abstract:
In today’s world, cancer is a leading cause of death among people of all ages and races. Research related to motility and cell adhesion could expand our knowledge of how cancer cells spread during metastasis and therefore, provide insights on how to prevent them from dispersing. A single-cellular, eukaryotic organism, the amoeba Dictyostelium discoideum, naturally adheres to a variety of substrates. Previous research in our lab has identified a novel adhesion receptor, named sadA. Cells lacking this receptor are unable to adhere to substrate (Fey et al, 2002). The sadA receptor was identified in a mutant resulting from a larger genetic screen, in which Dictyostelium cells were mutated and several mutants (such as 4C3, 1F12, sadA- null) lost their ability to adhere to substrate. The present research consists of three parts. The first part is an in-depth investigation on the adhesion properties (initiation and maintenance) of mutant 4C3; the results were compared to those of wild type Dictyostelium, and the previously analyzed mutant 1F12 (L. Nayak, research report 2002). From visual judgment, 4C3 cells appeared to have a greater adhesion capability than 1F12 cells, however 4C3 cells were unable to initiate or maintain adhesiveness when shaken (10 RPM). Therefore pictures of these mutants were taken to verify that mutant 4C3 did in fact adhere better than other mutants, but has a severe adhesion defect compared to wild type. The second part of this research investigates the cell adhesion properties of cells that might over-express the sadA receptor in comparison to wild type cells. However, the results showed that adhesion was not increased, suggesting that sadA is not over-expressed in these cells, or that over-expression of sadA does not lead to stronger adhesion. Finally, talin, a molecule that forms a link between the plasma membrane and the cytoskeleton might act in the same pathway as sadA. We tested talin null mutants (Niewöhner et al. 1997) for their cell adhesion abilities and concluded that the absence of the sadA receptor resulted in a more drastic loss in adhesion than the absence of talin.