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Research
Bridging spatial and temporal resolution gaps in the study of cell division
Our research focuses on the mechanisms that underlie faithful division of human cells. To obtain large volumes of high time-resolution information on cell division, we develop technology for high-throughput microscopy and mathematical modeling of cellular phenotypes. Furthermore, to bridge resolution gaps in the spatial domain, we integrate super-resolution fluorescence microscopy, electron microscopy, and live-cell imaging into correlative imaging workflows. Using these tools, we aim to elucidate how cytoskeletal and membrane systems shape emerging daughter cells and how signaling pathways coordinate the proper order of mitotic events.
Computer vision and machine learning
High throughput live-cell microscopy and systematic gene inactivation experiments are a key element of most research projects in the laboratory. To obtain quantitative and unbiased annotation of the TeraByte-scale imaging data sets, we develop multi-dimensional data visualization and machine learning methods, and mathematical models of cellular phenotypes (Figure 1).
Methodologies developed in our lab are available through the CellCognition software project (http://www.cellcognition.org), a platform for interactive assay design and high-performance computing of large image datasets on computer clusters.
Regulatory networks of mitosis and cytokinesis
The complex dynamics of chromosome segregation and cell division requires tight coordination between various cytoskeletal and membrane structures (Figure 2). The timely order of mitotic events involves complex regulatory networks of posttranslational modifications and protein degradation. By systematic perturbation experiments and kinetic analysis we aim to establish an integrated model of mitotic regulation, with a focus on mitotic exit and its interface to the spindle assembly checkpoint.
We are also particularly interested in understanding how chromosome segregation is temporally coordinated with cytokinesis, and how cells respond to errors in chromosome segregation.
Mechanism of cytokinetic abscission
Following partitioning of bulk cytoplasmic contents by cleavage furrow ingression, animal cells split by abscission. We recently identified a new type of 17 nm filaments at the cortex of the intercellular bridge (Figure 3), which is likely composed of the Endosomal Sorting Complex Required for Transport (ESCRT)-III. Our data indicate an abscission mechanism by cortical constriction with simultaneous disassembly of underlying microtubules by the severing enzyme Spastin.
Future work aims to elucidate the dynamic properties of 17 nm filaments and their force-generating mechanism, the biophysics of membrane fission, and the signalling networks that coordinate membrane dynamics and microtubule disassembly during abscission.
MicroRNAs in the regulation of cell division
Progression through the cell cycle is associated with stage-specific transcription, translation and regulated protein stability of a significant fraction of the transcriptome and proteome. Using a genome-wide approach, we aim to elucidate how microRNAs contribute to the control of cell cycle progression, and if and how microRNA biogenesis and function is regulated during the cell cycle.
- Figure 1 (click to view legend)
Figure 1: Automated live-cell microscopy. Time-lapse imaging of a human cell line expressing H2B-mCherry was processed by object detection, cell tracking, and automated classification of mitotic stages using CellCognition (http://www.cellcognition.org). Class transition probabilities were learned from the data for Hidden Markov modeling to improve classification accuracy. Colored contours indicate mitotic stages. Adapted from Held et al., Nature Methods (2010).
- Figure 2 (click to view legend)
- Figure 3 (click to view legend)
Figure 3: ESCRT-III-dependent 17 nm filaments at the abscission site. 17 nm filaments were visualized by electron tomography and reconstructed in 3D. 3D-structured illumination microscopy shows enrichment of the ESCRT-III core component CHMP4B at the abscission site. Adapted from Guizetti et al., Science (2011).
