Cell Polarity – Pattern formation at the single cell level
Previous and Current Research
Epithelial tissues are characterised by a pronounced apico-basal polarity, which is manifested by the asymmetric distribution of organelles or cytoplasmic proteins, and in the differentiation of the plasma membrane into two distinct domains, the apical and the baso-lateral domains (Fig. A). The apical domain can be further subdivided into spatially and functionally distinct regions, nicely seen in photoreceptor cells, where the apical domain is further subdivided into the rhabdomere and the stalk membrane (green and magenta, respectively, in Fig. B). Work in our group is aimed to understand the cellular, molecular and genetic mechanisms that control the establishment and maintenance of epithelial cell polarity. In particular we are interested to unravel the mechanisms that ensure the maintenance of the apical membrane when exposed to physical stress, e. g. during morphogenesis of epithelial tissues, or when exposed to light stress in photoreceptor cells, using Drosophila and zebrafish as model organisms.
One of the key players is the evolutionarily conserved Crumbs (Crb) protein complex. The complex is required
- for maintaining apico-basal cell polarity in epithelia;
- for regulating the proper size of the apical pole in epithelial and photoreceptor cells;
- for allowing proper morphogenesis of Drosophila photoreceptor cells;
- for preventing degeneration of photoreceptor cells and hence blindness, both in Drosophila and in human.
Future Projects and Goals
Current research in the group aims to unravel how the complex, which itself is localized apically, controls these processes. In addition, we are interested to identify additional mechanisms controlling apical-basal polarity and epithelial integrity, using genetic and biochemical approaches.
- What are constituents of the Crb complex, beside the known core components Crumbs, Stardust, DPATJ and DLin-7, and what is their function?
- How is the complex built and trafficked to the apical membrane?
- What is the importance of the recycling of the transmembrane protein Crumbs by the retromer?
- How does the Crumbs complex prevent light-dependent retinal degeneration?
- How is apico-basal polarity regulated in epithelia, which do not rely on the complex?
Methodological and Technical Expertise
- Drosophila genetics: fly husbandry, genetic screens, mapping of genes, clonal analysis establishment and analysis of transgenic flies.
- Light microscopy: preparation of embryos, larval, pupal and adult tissues for immune-histochemistry, study the specimens with confocal laserscanning microscopy, in-vivo imaging of embryos
- Electron microscopy: preparation of embryonic, larval and adult tissues of Drosophila and zebrafish for analysis by electron microscopy, immuno-electronmicroscopy
- Cell culture: standard cell culture techniques, transfection of cells, expression and purification of proteins
- Molecular biology and biochemistry: standard DNA-, RNA- and protein technologies, protein interaction. High throughput transcriptomic, proteomic and lipidomic analysis.
Pocha, S. M., Shevchenko, A. and Knust, E.
Crumbs regulates rhodopsin transport by interacting with and stabilizing myosin V.
J. Cell Biol. 195, 827–838 (2011)
Pocha, S. M., Wassmer, T., Niehage, C., Hoflack, B. and Knust, E.
Retromer controls epithelial cell polarity by trafficking the apical determinant Crumbs.
Curr. Biol. 21, 1111–1117 (2011)
Johnson, K., Grawe, F., Grzeschik, N. and Knust, E.
Drosophila Crumbs is required to inhibit light-induced photoreceptor degeneration.
Curr. Biol. 12, 1675–1680 (2002)
Wodarz, A., Hinz, U., Engelbert, M. and Knust, E.
Expression of Crumbs confers apical character on plasma membrane domains of ectodermal epithelia of Drosophila
Cell 82, 67–76 (1995)
Tepaß, U., Theres, C. and Knust, E.
The Drosophila gene crumbs encodes an EGF-like protein, expressed on apical membranes of epithelial cells and required for organization of epithelia.
Cell 61, 787–799 (1990)