Simanis lab – regulation of the cell cycle in mitosis and meiosis

The image shows wildtype and mutant S. pombe cells, stained with DAPI to reveal nuclei and Calcofluor to reveal the division site. A shows wild-type cells; note that cells divide in the middle, along the short axis. B shows cells that fail to signal cytokinesis; growth and nuclear division continue, producing multinucleated cells. C shows cells in which a cytokinesis signal is delivered constantly; they make multiple attempts at cytokinesis but cannot divide; D shows cells that cannot place the division site correctly. The image is assembled from multiple images. © Simanis lab.

Accuracy matters during the cell cycle; S-phase, mitosis and cytokinesis must be executed in the correct order, with high fidelity. Failure to do this may cause a cell’s death or alter its behaviour. An imprecisely executed meiosis may produce inviable gametes, or alter their ploidy. We study the spatial and temporal coordination of the cell cycle in meiosis and mitosis, using the fission yeast Schizosaccharomyces pombe as a model.

Genetic analysis of SIN function

the “standard model” for SIN signalling (see below and Simanis (2015) for details).

Coordination of SIN signalling with other cellular processes

coordination of cytokinesis with DNA synthesis and mitosis is essential. Ectopic activation of SIN signalling can trigger cytokinesis in interphase (bottom cell) or prematurely in mitosis (top cell), cutting the incompletely segregated chromosomes.

The role of the SIN and its regulators during meiosis

loss of Dma1p function in meiosis affects spore formation. Wildtype asci contain four spores; by contrast, without dma1-D function, diploids still produce four nuclei at the end of meiosis, but then fail to form a spore around one of more of them in more than 75% of asci.


Viesturs Simanis



Station 19

[email protected]


CH – 1015 Lausanne Switzerland