Our research has helped to show the connection between the development of the olfactory nerve and so-called GnRH cells (gonadotropin-releasing hormone cells). If the development of the olfactory nerve is disrupted, GnRH cells do not reach their final location near the pituitary gland. GnRH cells regulate sexual development and fertility, which cannot occur if this developmental stage shows a high degree of disruption. It is unusual combinations of genetic changes that underlie the disorders, which is in line with our working hypothesis that it is the interaction between many different types of cells that is involved in establishing a nerve. We address whether the so-called nerve-brain barrier cells participate in nerve establishment. The project is expected to show which precise step(s) in the formation of the olfactory nerve fails and thus causes lack of GnRH.By using the olfactory nerve as a model, new information is also expected on how nerve cell axons interact with a number of other, relatively little studied cell types to form and maintain the nerve-brain barrier. Nerves connect the periphery and the brain, making it important to know how the barrier allows axon passage but is not permeable to e.g. infectious agents, metastatic cells or toxic substances. Little is known about the cells of the barrier and how they are affected by nerve damage. The area around the olfactory nerve also contains an area for drainage of the fluid produced in the brain, making the healing process of the nerve-brain barrier in this area important to understand.