Myelin formation by Schwann cells in the absence of β4 integrin

The interaction of the Schwann cell with its basal lamina has been hypothesized to be an important prerequisite for the formation of a myelin sheath in the peripheral nervous system. One possible player in this interaction is β4 integrin; it is up‐regulated during myelin formation and, in association with α6 integrin, can interact with particular components of the Schwann cell basal lamina. In order to characterize the functional roles of β4 integrin during myelination, we investigated myelination in the absence of β4 integrin, i.e., in peripheral nerve tissue from β4 integrin‐deficient mice. Because the mutants die within several hours after birth, we cultured dorsal root ganglia from neonatal mutants under conditions that promote myelination, quantified the myelin segments by immunofluorescence, and investigated the ultrastructure of the cultured myelin sheaths. In another approach, we quantified the few myelin sheaths that are detectable in femoral nerves of newborn animals. Based on both approaches, we conclude that myelination by Schwann cells can occur in the absence of β4 integrin demonstrating that this Schwann cell component is dispensable for myelin formation in peripheral nerves. GLIA 27:269–274, 1999. © 1999 Wiley‐Liss, Inc.