Molecular control of boundary cap stem cell function

We wish to answer fundamental biological questions that will benefit future research into nervous system regeneration by studying a type of neural stem cells known as boundary cap stem cells. These embryonic cells reside in clusters on the borders of the spinal cord and brainstem, where nerves exit and enter to connect to the rest of the body. These clusters, the boundary caps, are thought to be important for the correct development of the nervous system in mammals. In addition, they have the potential to act as stem cells that could be used for nervous system repair and regeneration. For these reasons, we want to understand how boundary caps are formed, how they function in the embryo to aid nervous system development, and how they eventually become nerve cells and support cells to in the adult nervous system. To achieve these goals, we will explore the function of three types of molecules that were previously shown to regulate the behaviour of neurons and blood stem cells and are targetable by clinical drug therapies.

The vertebrate nervous system is comprised of the central nervous system (CNS), including the brain and spinal cord, and the peripheral nervous system (PNS), containing the autonomic and sensory nerves. Boundary caps (BC) are stem cell clusters on the surface of the embryonic brainstem and spinal cord that guard the interface between the CNS and PNS during embryogenesis by preventing cell body mixing between both compartments, whilst creating a permissive environment for axons to cross between them. After birth, BC stems cells contribute to PNS formation by differentiating into peripheral glia and sensory neurons. The absence of BCs in adults likely contributes to the failure of axons to regenerate across the PNS/CNS border, and the identification of the molecules and mechanisms that determine the fate of boundary caps will therefore fundamentally advance our understanding of PNS development. It will also open up new avenues for research into nervous system regeneration. Our pilot data suggest that the cell surface protein neuropilin 1 (NRP1) is expressed by BC stem cells in vivo and in vitro, and that NRP1 is an important regulator of BC formation, BC differentiation and sensory axon organisation. NRP1 is a well-established receptor for axon guidance molecules of the class 3 semaphorin family, but it also serves as a receptor for the vascular endothelial growth factor termed VEGF164. Spurred by these promising observations, we propose to define the precise role of NRP1 and its ligands in BC development, maintenance and differentiation using a combination of genetic analyses and BC stem cell cultures.

This main impact of this work will be a significant advancement of our knowledge of the mechanisms that control neural stem cell maintenance and differentiation in vitro and in vivo. This work should be of interest to clinician-scientists involved in developing novel therapeutics for patients with neurodegenerative disorders and/or neurological injury. In the long term, this work will likely be of interest to the commercial sector involved in stem cell therapies/regenerative medicine or developing VEGF therapies and interested in licensing their products for novel purposes. We aim to disseminate our findings to the commercial sector and to clinician specialists in the following ways. Firstly, the project investigator and co-investigator will present the work at national, European and international neuroscience conferences that are attended by both scientists and clinicians. Secondly, the project investigator will explore the potential of clinical application of our research by establishing relevant collaborations. Thirdly, should the project reveal novel signalling pathways that could be targeted in therapies, the project investigator will obtain advice how to protect and commercialise IPR arising from this project. Finally, we will publish our work in open-access journals and disseminate our findings to the public via the media and through teaching in schools and Universities.