The group addresses the important question of how vertebrate and invertebrate cells coordinate developmental behaviours with that of their neighbours. It is well established that one way to achieve this goal is that organizing cells secrete signaling molecules such as the Hedgehog (Hh) morphogens to instruct receiving cells in concentration-dependent manner. In vertebrates, the Hh family member Sonic Hh (Shh) is essential for patterning of the ventral neural tube, for specifying digit identities and for axon guidance. In the adult, Shh pathway activation has been implicated in maintaining the stem/cancer stem cell niche and in the progression of various cancers. Despite these important roles, various aspects of Hh solubilization, its transport and signaling function remain unclear.
In the past, we have established that Hhs are solubilized by proteolytic processing of their lipidated N- and C-terminal Hh peptides (called shedding)(Dierker et al., 2009; Ohlig et al., 2011; Ohlig et al., 2012). We also found that Hh shedding depends on accessory glycoproteins called heparan sulfate proteoglycans (HSPGs) (Grobe et al., 2005; Ortmann et al., 2015). HSPGs are extracellular proteins linked to highly anionic heparan sulfate (HS) glycosaminoglycan chains that bind Hhs and factors required for their regulated release (called Scubes)(Jakobs et al., 2014; Jakobs et al., 2016; Jakobs et al., 2017). Still, the hierarchical assembly and molecular structure of such Hh assembly and release platforms as determinants of subsequent Hh spreading and signaling are only poorly understood. Therefore, by using advanced microscopy in conjunction with biochemistry, we currently characterize the molecular mechanisms that govern dynamic Hh platform assembly as well as Hh platform structure and its molecular composition at the cell surface.
In a second line of research, we currently decipher Hh long-range transport in the Drosophila wing disc by site-directed mutagenesis of HS-binding Hh amino acids. So far, removal of selected Hh residues was found to vastly increase its signalling range, resulting in striking patterning abnormalities such as mirror-image duplications of anterior wing tissue, while other residues have the opposite role. These findings provide a new mechanism to explain the essential role of HSPGs for accurate, defined and robust Hh signalling during development.
- Macchi, M., Magalon, K., Zimmer, C., Peeva, E., El Waly, B., Brousse, B., Jaekel, S., Grobe, K., Kiefer, F., Williams, A., Cayre, M. and Durbec, P. (2020). Mature oligodendrocytes bordering lesions limit demyelination and favor myelin repair via heparan sulfate production. Elife. 2020;9 pii: e51735. doi: 10.7554/eLife.51735.
- Manikowski, D., Jakobs, P., Jboor, H. and Grobe K. (2019). Soluble Heparin and Heparan Sulfate Glycosaminoglycans Interfere with Sonic Hedgehog Solubilization and Receptor Binding. Molecules. pii: E1607. doi: 10.3390/molecules24081607.
- Nandadasa, S., Kraft, CM., Wang, LW., O’Donnell, A., Patel, R., Gee, HY., Grobe, K., Cox, TC., Hildebrandt, F. and Apte, SS. (2019). Secreted metalloproteases ADAMTS9 and ADAMTS20 have a non-canonical role in ciliary vesicle growth during ciliogenesis. Nat Commun. 10(1):953. doi: 10.1038/s41467-019-08520-7.
- Kastl, P., Manikowski, D., Steffes, G., Schürmann, S., Bandari, S., Klämbt, C. and Grobe K. (2018). Disrupting Hedgehog Cardin-Weintraub sequence and positioning changes cellular differentiation and compartmentalization in vivo. Development 145. doi:dev167221.
- Schürmann, S., Steffes, G., Manikowski, D., Kastl, P., Malkus, U., Bandari, S., Ohlig, S., Ortmann, C., Rebollido-Rios, R., Otto, M., Nüsse, H., Hoffmann, D., Klämbt, C., Galic, M., Klingauf, J. and Grobe K. (2018). Proteolytic processing of palmitoylated Hedgehog peptides specifies the 3-4 intervein region of the Drosophila wing. Elife. 7. pii: e33033. doi: 10.7554/eLife.33033.
- Jakobs, P., Schulz, P., Schürmann, S., Niland, S., Exner, S., Rebollido-Rios, R., Manikowski, D., Hoffmann, D., Seidler, D.G. and Grobe, K. (2017). Ca2+ coordination controls Sonic hedgehog structure and its Scube2-regulated release. J Cell Sci. 130(19), 3261-3271. doi: 10.1242/jcs.205872.
- Jakobs, P., Schulz, P., Ortmann, C., Schürmann, S., Exner, S., Rebollido-Rios, R., Dreier, R., Seidler, D.G. and Grobe, K. (2016). Bridging the gap: Heparan sulfate and Scube2 assemble Sonic hedgehog release complexes at the surface of producing cells. Sci Rep. 6: 26435
- Ortmann, C., Pickhinke, U., Exner, S., Ohlig, S., Lawrence, R., Jboor, H., Dreier, R. and Grobe K. (2015). Sonic hedgehog processing and release are regulated by glypican heparan sulfate proteoglycans. J Cell Sci. 128(12): 2374-85
- Ohlig, S., Farshi, P., Pickhinke, U., van den Boom, J., Höing, S., Jakuschev, S., Hoffmann, D., Dreier, R., Schöler, HR., Dierker, T., Bordych, C. and Grobe, K. (2011). Sonic Hedgehog Shedding Results in Functional Activation of the Solubilized Protein. Dev. Cell 20, 764-774