Developmental expression of OSP/claudin-11

Oligodendrocyte‐specific protein (OSP/claudin‐11) is a major component of CNS myelin and has been recently added to the claudin family of tight junction proteins. In this study, the developmental expression of OSP/claudin‐11 was determined using in situ hybridization, immunohistochemistry (IH), and Western blot analysis. OSP/claudin‐11 mRNA was expressed in a bimodal fashion. During prenatal development, OSP/claudin‐11 mRNA was abundant in developing meninges, in areas adjacent to cartilage, and in mesoderm. In postnatal animals, OSP/claudin‐11 was expressed primarily in developing oligodendrocytes and to a lesser extent, in testes. Double‐labeled IH using O2‐A progenitor cells revealed that OSP/claudin‐11 expression occurs from the early progenitor stage and continues in mature oligodendrocytes. Electron microscopic IH localized OSP/claudin‐11 to laminar myelin in the adult CNS. Western blot analysis of OSP/claudin‐11 in developing brain revealed the expression of two separate transcripts that were developmentally regulated. These data demonstrate that OSP/claudin‐11 expression is highly regulated during development and, therefore, may play an important role in growth and differentiation of oligodendrocytes and other cells outside the CNS. J. Neurosci. Res. 3:284–290, 2000 © 2000 Wiley‐Liss, Inc.