P 0 -Cre Transgenic Mice for Inactivation of Adhesion Molecules in Schwann Cells.

Normal peripheral nerve myelination depends on Schwann cell-basal lamina interactions. An important component of Schwann cell basal lamina is laminin-predominantly laminins 2 and 4. Mutations in the alpha 2 chain common to these two isoforms are associated with dysmyelination in mouse (dy) and man (congenital muscular dystrophy). Thus, laminin 2 and 4 receptors are also likely to be important for myelin formation. Several laminin 2/4 receptors are detected at the basal lamina surface of myelin-forming Schwann cells, namely, α6β4 and α6β1 integrins and dystroglycan. The evidence linking these receptors to myelination is suggestive, but not conclusive. Genetic studies have not yet confirmed a role for these molecules in myelin formation. Natural or targeted inactivation of α6, β4, and β1 integrins and of dystroglycan have profound effects on other tissues causing embryonic or perinatal death before myelination. Therefore, to conditionally inactivate these receptors specifically in myelin-forming Schwann cells, we have constructed and initially characterized a P ₀ -Cre transgene that activates Cre-mediated recombination of loxP-containing genes in peripheral nerve.