PD Dr. Kay Grobe                   

University of Münster
Institute for Physiological Chemistry & Pathobiochemistry
Waldeyerstraße 15
48149 Münster

The main focus of PD Dr. Grobes group, located in the Department of Physiological Chemistry and Pathobiochemistry at the University of Münster, Germany, is the characterization of cell surface Heparan sulfate (HS)/growth factor interactions, their regulation on the level of HS synthesis and the characterization of mouse mutants made deficient in particular HS-biosynthetic genes. HS is produced by most mammalian cell types in the Golgi compartment on proteoglycan core proteins and is subsequently secreted to the cell surface. Many growth factors, chemokines, cytokines and morphogens bind to cell surface HS, and the proteoglycans are thought to act as co-receptors for these ligands. During development, these interactions are of great importance as they are thought to establish gradients of soluble signaling factors in the vicinity of their production. Cells surrounding the source of a particular signal can then respond in a graded manner according to the concentration of that signal and their HS “makeup”, resulting in patterns of cell types important for the final body plan. Not surprisingly, then, defects in the synthesis of HS proteoglycans result in a number of human diseases and developmental defects in the mouse, among them the hereditary bone disease HME (Hereditary Multiple Exostosis, a skeletal disorder characterized by the formation of abnormal bony growths) and Simpson-Golabi-Behmel syndrome (characterized by a wide variety of clinical manifestations including prenatal and postnatal overgrowth syndrome). Also, consistent with their multiple functions, defects in HS-proteoglycans have been involved in tumor progression, pathogenesis of Alzheimers disease, pathogen entry into cells, various common developmental defects and have even been implicated in regulating behaviour and memory in mice.

Our team presently analyzes three systemic and conditional (Cre/loxP) mouse mutants defective in HS synthesis. Mice deficient in Ndst1 function produce normal amounts of HS, but show altered HS sulfation patterns and growth factor binding properties. Mice die neonatally, showing severe developmental defects of the head, eyes, heart, skeleton and forebrain. These defects are consistent with impaired Sonic hedgehog (Shh) and fibroblast growth factor (Fgf) function. Using chemical and biochemical methods, we are now in the process to characterize the molecular basis for those defects. A particular focus lies on the molecular characterization of Shh/HS interactions. Here, the major goal is to understand how HS mediates the release of the biologically active, doubly lipidated signaling molecule ShhNp from the cell surface of Shh-producing cells, and how HS participates in the formation of Shh morphogen gradients. To achieve these goals, collaborations exist with national as well as international collaborators. Moreover, we have recently added the Drosophila system as an established tool to rapidly test and confirm in vitro data in vivo.
Methods used: molecular biology, recombinant protein production and purification, (stem) cell culture, histology, PCR, real-time PCR, protein analytics, carbohydrate analytics (HPLC and MS), FPLC, in situ hybridization, immunofluorescence- and confocal microscopy.

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