Cell division is a necessary process for growth and development. Fission yeast (S. pombe) provides a model system for polarity and cytokinetic mechanisms because, like human cells, they grow in a bipolar fashion and divide symmetrically. Mid1 is a founding protein of the cell division machinery and defines the division plane. Without Mid1, there is incomplete, uneven division. The orb mutants are classified by a loss of cell polarity and round shape. To study the relationship between polarity and cell division, we examined interactions between Mid1 and orb mutants. These orbmutants show more binucleate cells with internal septa, paired configurations where two cells are not completely separated, and differing localizations of Mid1. Specifically, Mid1 appears more concentrated at subcellular sites in the orb6 mutants, suggesting higher protein levels. These phenotypes suggest a relationship between cytokinetic defects and the polarity genes, as well as a link between Mid1 and the Orb proteins.
Faculty Mentor: Dawn Clifford Hart, Cell & Molecular Biology