Expression of extracellular matrix molecules and cell surface molecules in the olfactory nerve pathway during early development

Abstract

The spatial and temporal expression patterns of several extracellular matrix molecules--laminin and fibronectin and cell surface molecules, neural cell adhesion molecule (NCAM), L1, tenascin, chondroitin sulfate proteoglycan, and peanut agglutinin (PNA) binding sites--were investigated during early olfactory nerve development. NCAM and L1 have similar patterns: They are expressed in the olfactory nerve and on the olfactory receptor neurons (ORNs) commencing with the earliest olfactory axon outgrowth (E12-E15). Their expression patterns suggest that both NCAM and L1 are associated with extension and fasciculation of olfactory axons. A comparison of L1 and olfactory marker protein suggests that L1 is expressed predominantly on immature ORNs. Laminin has an unique punctate staining pattern in the developing olfactory pathway as early as E12. These laminin puncta might play a role in olfactory neurite outgrowth and guidance. At E14, when pioneer olfactory axons enter the brain, the laminin-positive meninges on the surface of the olfactory bulb primordium break down but remain intact in the rest of the telencephalon. This suggests a functional interaction between the olfactory axons and the glial-pial barrier. Fibronectin staining is diffuse throughout the cranial mesenchyme but is absent from the olfactory nerve pathway. No specific patterns of tenascin or chondroitin sulfate, were observed during early olfactory development. PNA binding sites were associated with olfactory axon fasciculation. The expression of several extracellular matrix molecules and cell surface molecules is spatially and temporally regulated in the developing olfactory system. These molecules, thus, may play functional roles in olfactory axon outgrowth, fasciculation, and/or guidance.

Activation of theWnt–βCatenin Pathway in a Cell Population on the Surface of the Forebrain Is Essential for the Establishment of Olfactory Axon Connections

“…This BM is composed of laminin, collagen-IV, and proteoglycans of the CSPG and the HSPG classes (Gong and Shipley, 1996;Treloar et al, 1996;Julliard and Hartmann, 1998). The position of ␤galϩ nuclei with respect to the BM was assessed by double immunostaining for ␤gal and either collagen-IV or HSPG, on E12.5 and E14.5 BAT nlacZ embryonic heads.…”

“…Beginning at embryonic day 10 (E10), immature olfactory receptor neurons (ORNs) in the olfactory placode (OP) extend axons toward the forebrain (FB) along with several populations of migratory cells (Gong and Shipley, 1996). This meshwork of neurites and migratory cells form a migratory mass (MM) that remains separated from the FB by the basement membrane (BM).…”

The role of Dlx homeogenes in early development of the olfactory pathway

“…Forebrain basement membrane is unfenestrated in Dlx5-/-embryos At approximately E14.5 during mouse embryo development the BM of the OB region is fenestrated and then eliminated to allow the MM to form the OB nerve layer (Gong and Shipley 1996;Treloar et al 1996). We have examined the organization of the BM (see Julliard and Hartmann 1998) in Dlx5-/-mice by immunostaining with antibodies that recognize laminin, collagen-IV, heparan-sulfate proteoglycan (HSPG), chondroitin-sulfate proteoglycan (CSPG), on sections of WT and Dlx5 lacZ -/-embryonic noses at E12.5, E14.5 and P0.…”

“…A small number of pioneer axons enter the FB at earlier stages (Astic et al 2002;Key 1998), but their function is still unclear. At later stages (E13.5-E14.5) the basement membrane (BM) separating the MM from the olfactory bulb (OB) is degraded allowing massive entry of ORN axons and the formation of the outer sublaminae of the nerve layer (Doucette 1989;Gong and Shipley 1996;Bailey et al 1999;Au et al 2002).…”

Novel Microglomerular Structures in the Olfactory Bulb of Mice

“…In developing (Terkelsen et al, 1989;Gong and Shipley, 1996;Treloar et al, 1997) and mature (Yamashita et al, 1998) mice, OSNs that target the MOB and AOB strongly express NCAM in their cell bodies and axons. To assess the presence of NCAM in microglomeruli, we double-labeled olfactory bulbs with UEA and NCAM (Fig.…”