Dresden 2011 – wissenschaftliches Programm

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BP: Fachverband Biologische Physik

BP 24: Physics of Cells II

BP 24.5: Vortrag

Donnerstag, 17. März 2011, 11:15–11:30, ZEU 250

Mechanics of Spindle Alignment in Saccharomyces cerevisiae — •Stephan Baumgärtner, Hannes Weisse, and Iva Tolic-Nørrelykke — Max-Planck-Institute for Cell Biology and Genetics, Dresden

Asymmetric cell devisions are an important process for cell differentiation in higher organisms. To study such divisons, the asymmetric dividing fungus Saccharomyces cerevisiae is an excellent model. It is essential for finishing cytokinesis to orient the mitotic spindle along the mother-bud axis for proper chromosome segregation. In an early pathway (PW), the older of the two spindle pole bodies (oSPB) is moved towards the mother-bud neck by astral microtubules (aMT). During a late PW, the aMTs grow inside the bud and get captured by the dynein anchor Num1 located in the bud cell cortex. Dynein translocates the oSPB through the neck by pulling on the aMTs.

Fast live cell imaging, quantitative image analysis and mathematical modeling is applied. Wild-type (WT) cells and cells lacking the early PW nearly all finished translocation of the spindle within 30 minutes from the onset of mitosis (spindle L ≥ 2µ m), only 80% of the cells lacking the late PW were able to do so. The spindle movement often shows pulling events (PE), i.e. rapid jumps of the spindle. In WT cells, these PE more often occur after the oSPB entered the bud. Cells lacking the late PW show much less PE and cells without the early PW show hardly any PE before the spindle entering. Thus, the efficiency of the delivery of the oSPB to the daughter cell depends mainly on the late PW, whereas the early PW is required to orient the spindle.