Our lab is interested in understanding the cellular mechanisms involved in the control of the intracellular space and cell morphogenesis. To study these mechanisms at a molecular and cellular level we use a simple eukaryote, genetically tractable fission yeast Schyzosaccharomyces pombe, as a model organism.
S. pombe is a cylindrical single-celled yeast that grows in a highly polarized manner by tip extension. Once cells reach a critical cell mass, mitosis is initiated and chromosomes are segregated along the long axis of the cell. Cells then divide symmetrically generating two identically sized daughter cells.
Fission yeast precisely position growth zones to the opposite cell ends in order to grow in a straight line. They also define cell middle to position cell division site.

 

S. pombe cytoskeleton consists of actin filaments, actin cables and microtubules (MTs). Disruption of the MT cytoskeleton results in defects on nuclear and division plane positioning as well as defects in the establishment of sites of growth and cell shape. Interphase MTs are highly dynamic and are organized into antiparallel bundles with the plus ends facing the cell tips and the minus ends overlapping near the cell center where these bundles are attached to the nuclear envelope. This simple MT organization allows S. pombe cells to deliver polarity factors to the cell tips and to position the nucleus at the geometrical center of the cell. Actin filaments are also polarized within the cell with the barbed, fast growing, ends facing the cell tips during interphase and the cell center during cytokinesis. This polarization allows myosin V-driven transport of secretory vesicles towards the sites of growth and division. Defects in actin cytoskeleton or actin-dependent transport result in loss of polarized growth and in cell shape defects.

1. Which molecular mechanisms allow cells to sense their cellular space and determine/find their geometrical center (needed to position the nucleus in the cell middle and to divide symetrically forming identical daughters),
2. How do cells determine the sites of growth and division,
3. How is a particular cellular shape established and maintained, and
4. How does the mitotic spindle interpret cellular shape and polarity cues to orient itself along the long axis of the cell.