Prof. Dr. Silvio O. Rizzoli
Super-resolution microscopy: from 50 to 5 nm, and from 2 € to 4,000,000 €
To understand the functional organization of the cell, meaning the connection between the topological distribution of cellular elements (such as proteins or organelles) and their function, one needs to rely on imaging beyond the resolution limit. Several such technologies exist, including stimulated emission depletion (STED) microscopy or stochastic optical reconstruction microscopy (STORM), which produce enhanced images by temporally separating the emitted photons. The more recently invented expansion microscopy achieves similar resolution by enlarging the sample, while using conventional microscopy optics. Nevertheless, one important aspect is missing from this type of analysis: an imaging-based measurement of the turnover of the cells and tissues. For example, it is unclear whether the state of activity of a synapses is related to its turnover, or whether the lack of activity that is caused by synaptic disease translates into local changes in turnover, at the level of the synapses that are affected by the disease. This type of question could be extended to every tissue, and to every organelle, in the entire biomedical field of research. To answer it, one needs a different technique: an instrument that can image, at high spatial resolution and with high sensitivity, the turnover of the structures of interest. This has been recently covered by nanoscale secondary ion mass spectrometry (nanoSIMS), which is currently reaching resolutions of down to 1 nm in the axial direction.
Major Research Interests
Conventional fluorescence microscopy is limited by the diffraction of light: fluorescent objects that are close together cannot be discerned. Stimulated emission depletion (STED) is a recent advancement in optical physics that breaks the diffraction barrier, allowing microscopes to obtain much clearer images.
The diffraction barrier has been particularly problematic for imaging synaptic vesicles, which are among the smallest known organelles (30-50 nm in diameter). They are located in small areas in the synapses (about 1 micron in diameter). The group takes advantage of the increased imaging resolution provided by STED to investigate synaptic vesicle function, with an emphasis on synaptic vesicle recycling. Since STED microscopy also allows imaging of protein domains, the group aims at studying the patterning of protein domains in the synapse, in order to understand its molecular architecture.