Dr. Andrew Goryachev, Centre for Systems Biology, School of Biological Sciences, University of Edinburgh
Monday 16th December, 4.00 p.m., Stacey Lecture Theatre 1
Budding yeast is an ideal model organism to study biophysical principles underlying eukaryotic cellular morphogenesis. Rather than dividing its cell in halves, this unicellular fungus proliferates by constructing every new daughter cell de-novo, on the side of mother cell. This process is an amazing example of building a cell from scratch. It starts with the establishment of a new cell polarity axis, which is physically marked by a membrane domain, presumptive bud site (PBS), whose protein-lipid composition is distinctly different from the rest of the cell. This and the whole cascade of downstream morphogenetic processes are controlled by a single master regulator – small GTPase Cdc42. Its biological activity is directly responsible for the assembly of the PBS and the following formation of the septin ring, a dense polymeric organelle that serves as the boundary between mother and daughter until they are finally split apart by cytokinesis. Septin rings are found at the cytokinetic sites of fungi, in the tails of spermatozoa as well as at the base of neural spines and eukaryotic cilia – all places where contiguous membrane has to be divided into two non-mixing domains with distinct biological properties and developmental fates. Yet, despite the utmost importance of this organelle for eukaryotic cells, molecular mechanisms responsible for the formation of these rings are not known in any system. As often before, budding yeast comes to the rescue again. In this talk I will present the results of our recent experiment-theory study aimed to unravel the mystery of septin ring emergence in budding yeast. Among others, I will answer a long-standing question: How does it become a ring in the first place?
Keywords: cell polarity, cellular morphogenesis, small GTPases, Cdc42, septin ring, diffusion barrier, Turing model, reaction-diffusion equations, experiment-theory study.