MuVi-SPIM image of a Drosophila embryo. Eight views were fused to yield an in toto reconstruction of the embryo (one side membrane unrolled).

Figure 1: MuVi-SPIM image of a Drosophila embryo. Eight views were fused to yield an in toto reconstruction of the embryo (one side membrane unrolled). The high speed of the microscope enables a detailed reconstruction of cell lineage and shape changes over extended periods of development.

The Hufnagel group studies the role of mechanical constraints in processes such as cell growth, programmed cell death, orientation of cell division, intratissue rearrangements and cell differentiation.

Previous and current research

Biological processes are highly dynamic and span many temporal and spatial scales. During development, cells must integrate and respond to a multitude of biochemical and biophysical signals: for example, changes in intracellular signalling networks, cytoskeleton remodelling, cell shape changes, long-range signalling and tissue remodelling. A whole-embryo view of morphogenesis with subcellular resolution is essential for unravelling the interconnected dynamics at varying scales of development – from interactions within cells to those acting across the whole embryo. Bridging scales from the submicron to the millimetre range with a temporal resolution of several seconds – combined with a total imaging time of several hours – not only poses tremendous challenges for modern microscopy methods but also requires powerful computational approaches for data handling, processing, and image analysis.

The central question that we are interested in is how a complex multi-cellular tissue or organism is formed from individual cells by spatio-temporal regulation of biophysical and intracellular signalling processes. We address all experimental steps, from innovative transgenic lines and microscope development to systematic image processing and biophysical modelling. This requires a multidisciplinary environment of biologists, physicists and computer scientists working closely together.

In order to address these questions we develop novel imaging techniques based on selective plane illumination microscopy (SPIM). SPIM yields optical sectioning by uncoupling the optical path for sample illumination from emitted photon detection. The illumination branch creates a thin light sheet to illuminate a specimen from the side and the emitted light is collected and imaged onto a high speed and high sensitivity camera by a second objective lens. The unprecedented speed of light sheet-based microscopy poses challenges for data handling and image processing, which we address by developing novel image processing tools.

Currently, we investigate cell shape changes and growth patterns in the Drosophila embryo with emphasis on the role of mechanical constraints on organ formation and tissue differentiation, complemented by mammalian cell culture studies investigating cell cycle response of an epithelial tissue to external and internal mechanical perturbations. Our group is part of the Centre for Modelling and Simulations in the Biosciences (BIOMS).

Future projects and goals

We are focused on the control and regulation of cell proliferation, apoptosis and cellular rearrangement processes in developing tissues, with a specific emphasis on epithelial tissues and the role of mechanical interactions as a regulator. We seek to characterise and quantify the spatio-temporal effects of mechanical stress, deformations and fluid flow-induced sheer stress on cell growth, gene expression and cellular polarity in two-dimensional epithelial tissues. To address this issue, we pursue an interdisciplinary approach combining classical biological techniques with detailed modelling methods from various fields, ranging from statistical physics to applied mathematics and computer science. We will continue to not only tailor light-sheet microscopes to match specific biological questions, but also push the boundaries of light-sheet microscopy towards high speed intracellular imaging with extremely thin light sheets, super-resolution techniques, and quantitative in toto imaging.