Figure 1: Embryonic pre-implantation development: Tracking of all cells throughout the first mitotic divisions, from zygote to blastocyst stage, using an inverted light-sheet microscope. Nuclei detected by their H2B signal are shown. Colour-coded spheres indicate cells of different fate: trophoectoderm (TE; blue) or inner cell mass (ICM; red) (Strnad P et al. 2016).
The Ellenberg group studies how cells divide and organise in mitosis and meiosis, where errors can lead to problems such as cancer and infertility.
Previous and current research
Our overall goal is to systematically elucidate the mechanisms underlying cell division and nuclear organisation. We are developing a broad range of advanced fluorescence-based imaging technologies to assay the functions of the involved molecular machinery non-invasively, automate imaging to address all its molecular components, and computationally process image data to extract biochemical and biophysical parameters. Our research focuses on three areas: systems biology of mitosis, nuclear structure, and molecular mechanisms of meiosis and early embryonic mitosis.
We have previously identified hundreds of new cell division genes by RNAi-based screening of the entire human genome and we are now studying – in live cells and with high-throughput – protein function, interactions and networks during somatic mitosis by automating advanced fluorescence imaging and single molecule techniques, such as fluorescence (cross) correlation spectroscopy.
We also determined the positions of various nuclear pore complex (NPC) components and directly resolved the ring-like structure of the NPC, combining stochastic super-resolution microscopy (SRM) with single particle averaging. Currently, we elucidate the assembly mechanism of the NPC and chromatin dynamics over the cell cycle.
By complete kinetochore tracking we demonstrated that meiotic chromosome biorientation is highly error-prone. We have now developed a gentle light-sheet-based microscope for high-throughput imaging of mouse oocytes and embryos to enable systematic molecular analysis of meiosis and early embryonic mitosis (figure 1).
Figure 2: A 3D metaphase model reconstructed from confocal images of HeLa cells. The colours identify different elements / proteins important for mitosis (centrosome, cyan; chromatin, green; kinetochores / centromeres, red).
Future projects and goals
We want to gain comprehensive mechanistic insight into the division of human mitotic cells, provide a biophysical basis to understand nuclear organisation, and establish methods for systems analysis of the meiotic and first mitotic divisions of mammalian oocytes and embryos.
For a systems-level understanding of all crucial protein interactions during cell division, we will combine automated bulk, single molecule imaging and computational data analysis with advanced machine learning and modelling approaches to integrate all interactions into one canonical 4D model of a human dividing cell (figure 2).
To come to a structural understanding of nuclear organisation, we will explore and further improve correlative imaging approaches, combining live cell confocal microscopy, SRM and electron tomography to unravel the mechanism of NPC assembly and disassembly, as well as the human genome architecture, chromatin organisation and compaction.
To be able to apply systems biology tools to oocyte meiosis and early embryonic mitosis, we will push light-sheet-based imaging technology development further to improve its light efficiency and resolution in order to establish a physiological molecular model for early mammalian development and infertility.