Dynamic interactions between neuronal cells determine key morphological and functional properties of the nervous system during ontogeny and adult life. This is perhaps most profoundly illustrated by the elaboration of the myelin sheet that surrounds many axons and by the assembly and dynamics of the neuronal synapse. Members of the neuronal ADAM receptor family and their extracellular ligands, the LGI proteins, play critical, but as yet poorly understood roles in these dynamic interactions. ADAM and LGI proteins have been associated with tumorigenesis, hereditary forms of epilepsy, limbic encephalitis and amyelination. These diverse neurological diseases are not only a reflection of distinct expression patterns of the individual ADAM and LGI proteins but also reflect functional differences between these proteins.
 We use myelination of peripheral nerves and formation of the pinceau synapse in the cerebellum as experimental systems to study the role of LGI and ADAM proteins in different cellular interactions and gain insight into common and distinct mechanisms of their action. I will present our recent work on LGI2 and LGI4 and their ADAM receptors and discuss their role in potassium channel clustering and myelination.