A role for tenascin-like molecules in developing olfactory glomeruli.

Abstract

The distribution and potential functions of extracellular matrix and cell-surface molecules during neural development were explored, using an insect olfactory system as a model. Immunocytochemical and biochemical experiments were performed to examine the cellular localization and temporal pattern of expression of molecules similar to the vertebrate extracellular matrix molecule tenascin. These studies showed that tenascin-like molecules were associated with glial cells that form borders around distinct units of neuropil called glomeruli. These molecules were present at critical times during the glomerulus formation. In vitro assays, performed to examine the effects of tenascin on the morphological development of moth CNS neurons, indicated that the growth of these neurons was inhibited by tenascin. Taken together, these results suggest that glial cells decorated with tenascin-like molecules could contribute to the patterning of the olfactory neuropil by constraining neurite outgrowth within developing glomeruli. The distribution of other glycosylated molecules that could play important developmental roles was examined using the lectin peanut agglutinin. This lectin labeled the tips of dendrites as they grow into developing glomeruli to interact with glial cells or sensory axons. Four lectin-labeled proteins were shown to be developmentally regulated and thus could participate in neurite outgrowth, synapse formation or the stabilization of glomerular units. Future experiments to further explore molecular mechanisms underlying the development of neural architecture are proposed. The results of this study are discussed in the context of dynamic interactions between neurons and glial cells.