For master students at UniGE, the lab offers several possible master projects in which you can learn a wide range of techniques. Projects are typically multi-disciplinary, including techniques such as molecular cloning, molecular genetics, live-cell imaging, correlative light-electron microscopy, or biochemical methods. Below are a couple of examples. If you are interested in discovering more, come and talk to us!

STUDY OF THE SEPTIN CYTOSKELETON DURING CELL-CELL FUSION

Septins are highly conserved cytoskeletal GTP-binding proteins, expressed in most eukaryotic cell types. Septin monomers interact with each other to form oligomeric structures that can in turn organize in higher-ordered structures, such as filaments or rings. These cytoskeletal structures interact with membranes and have a conserved role as scaffold for the recruitment of other proteins and as cortical barriers to prevent free diffusion of proteins between different compartments. Fission yeast cells express seven septins: Spn1-4 are expressed during mitotic growth while Spn5-7 are expressed during sporulation and are important for proper forespore membrane formation. During the sexual lifecycle, septins are found at shmoo projections and cell-cell contact site before cell-cell fusion. Preliminary experiments show that deletion of septin subunits impairs fusion efficiency and neck expansion.

The master student will characterize in detail the phenotype of septin mutants and study septin localization during the mating process. Moreover, the candidate will use super resolution microscopy techniques to first define the septin structure throughout the fusion process.

How do yeast cells choose their mate?

During mating, fission yeast cells communicate with potential partners using pheromones. Our research has shown that this communication happens in local polarity patches that are mobile over the cell periphery, resembling a form of ‘speed dating’ (Merlini et al. 2016). We found that, when compared to the lab strain, fission yeast strains obtained from the wild exhibit reduced mating efficiency, and some exhibit an altered mating preference, exhibiting a non-random choice of partner. We aim to understand the genetic basis of this altered partner selection. One hypothesis is that the polarity patch dynamics has changed in these strains resulting in the altered mating preference. The master student will investigate the polarity patch dynamics of selected wild fission yeast strains by following fluorescent markers of the polarity patch in these strains by live-cell imaging. In this internship, the student will learn to use molecular genetics, cloning, yeast transformations, live-cell imaging by fluorescence microscopy and image analysis techniques.

MAPK signaling during sexual reproduction

During sexual reproduction, gametes fuse together to form the diploid zygote. In fission yeast cells, mating depends on pheromone signaling between partner cells, which triggers a conserved signaling pathway from a G-protein-coupled receptor (GPCR) through a MAPK signaling cascade. This GPCR-MAPK signaling is not only essential to induce the transcriptional changes that promote sexual differentiation, but also acts locally at the site of partner cell contact to promote cell-cell fusion (Dudin et al. 2016). To dissect the mechanisms of this signaling pathway, we have conducted phospho-proteomic screens, identifying candidate MAPK substrates. In this project, the master student will investigate the possible role and localization of candidate MAPK substrates, by constructing deletion and tagged strains, as well as strains in which the identified phosphorylation sites are mutated. For substrates with interesting location/phenotype, further analysis will involve in vitro work to confirm direct phosphorylation by the MAPK. In this internship, the student will learn to use molecular biology, yeast molecular genetics (including CRISPR), live-cell imaging, in vitro kinase assays.