Extracellular matrix and development of lamination in the dorsal lateral geniculate nucleus in the tree shrew (Tupaia belangeri)

In the tree shrew (Tupaia belangeri), the cytoarchitectonic lamination of the lateral geniculate nucleus cannot be detected at birth; it only appears during the early postnatal period. However, a laminated pattern was revealed with rapid Golgi staining and retinal afferents were segregated into the appropriate laminae well before cytoarchitectonic lamination could be seen. Both observations indicate that the extracellular matrix may play a role in the separation of lateral geniculate nucleus cells into laminae. In the present study, the organization of the extracellular matrix was investigated during development using immunohistochemical and in situ hybridization techniques. For immunohistochemistry, peanut agglutinin (PNA) lectin and antibodies against tenascin (TN) were chosen, while for in situ hybridization, mTN riboprobes were used, simultaneously, with antibodies against Vimentin (Vim) and microtubule associated protein (MAP-2). The results showed that the pattern of PNA-binding glycoproteins and that of tenascin were relatively similar, although tenascin appeared later and disappeared earlier. The first interlaminar spaces to be detected were those between layers innervated by opposite eyes. The TN specific mRNA was detected in the lateral geniculate nucleus at P0, but was no longer visible at P7. By comparing TN mRNA and Vim or MAP-2 stainings a correspondence could be observed. The extracellular matrix lamination therefore seems to precede cytoarchitectonic lamination, suggesting that the extracellular matrix may play a role in the development of laminated structures. The TN-producing cells seem to be developing astrocytes and neurons.