You might recall that age-related thinning of the myelin that insulates nerves strongly correlates with declining brain function. Researchers investigating MS are making progress into the mechanisms by which this happens: the protein netrin-1 "is known to guide and direct nerve cell axons to their targets. ... blocking the function of netrin-1 and one of its receptors in adult neural tissue causes the disruption of myelin. ... We've known for just over 10 years that netrin is essential for normal development of the nervous system, and we also knew that netrin was present in the adult brain, but we didn't know why. ... the new findings show that netrin-1 and its receptor are needed to hold paranodal junctions in place, and thereby maintain the structure of myelin. The paranodal junction is a highly specialized region of contact where an oligodendrocyte cell attaches itself to the nerve cell's axon. This juncture acts as a molecular fence, which organizes and segregates the distribution of key proteins along the nerve cells axon and plays an imperative role in the proper conduction of electrical signals along the length of the nerve cell. When the function of netrin-1 and its receptor is disrupted, the organization of this adhesive junction comes apart, disrupting the function of nerve cells in the brain and spinal cord."