The role of Wnt proteins in symmetric/asymmetric division of the mammary stem cells
Final Report Abstract
Wnt proteins form a family of highly conserved signaling molecules that regulate cell-to-cell interactions during embryogenesis and adult homeostasis. Wnt proteins are secreted as hydrophobic lipid modified glycoproteins. Purified Wnt proteins are highly insoluble and require detergent to maintain them in solution. The presence of detergent can limit the amount of Wnt added to the cells due to its toxicity. In my study I developed a novel method to covalently immobilize Wnt proteins to a glass surface in the absence of detergent. The immobilized Wnt proteins activate the Wnt signaling pathway in various Wnt responsive cell lines. The immobilized Wnt proteins can be stored for long periods of time without losing their biological activity. Furthermore, I have demonstrated that the activity of immobilized Wnt proteins can be maintained for a longer period of time in culture than when compared to the soluble form of Wnt proteins. This novel method will allow us to provide a more active and stable source of Wnt that can be used at higher concentrations for a variety of applications including longer-term cell culture and for the first time, the ability to present Wnt proteins alone to the cell in a spatially controlled manner. With this tool, I study the effect of a local source of Wnt proteins on the division mode of a purified population of mammary gland stem cells (MaSCs). I succeeded in establishing a protocol for culturing the MaSCs on the immobilized Wnt surface. By using time-lapse imaging, I aim to follow the division mode and the fate decision of MaSCs. To that end I will monitor the distribution of cell surface markers specific to MaSCs and the spindle orientation of the dividing cell as compared to the location of the immobilized Wnt proteins. In summary, I succeeded in establishing a system that aims to answer a fundamental question in stem cell biology: whether asymmetric divisions of stem cells are controlled by polar signals.
Publications
- (2010) A study on the interaction between heparan sulfate proteoglycans and Wnt proteins. Dev Dynamics. 293(1): 184-190
Fuerer C., S.J. Habib and R. Nusse
