Contribution of heparan sulfate to the non-permissive role of the midline glia to the growth of midbrain neurites.
Radial glial cells and astrocytes are heterogeneous with respect to morphology, cytoskeletal- and membrane-associated molecules and intercellular interactions. Astrocytes derived from lateral (L) and medial (M) midbrain sectors differ in their abilities to support neuritic growth of midbrain neurons in coculture (Garcia-Abreu et al. J Neurosci Res 40:471, 1995). There is a correlation between these abilities and the differential patterns of laminin (LN) organization that is fibrillar in growth-permissive L astrocytes and punctate in the non-permissive M astroglia (Garcia-Abreu et al. NeuroReport 6:761, 1995). There are also differences in the production of glycosaminoglycans (GAGs) by L and M midbrain astrocytes (Garcia-Abreu et al. Glia 17:339, 1996). We show that the relative amounts of the glycoproteins laminin LN, fibronectin (FN) and tenascin (TN) are virtually identical in L and M glia, thus, confirming that an abundant content of LN is not sufficient to promote neurite growth. To further analyze the role of GAGs in the properties of M and L glia, we employed enzymatic degradation of the GAGs chondroitin sulfate (CS) and heparan sulfate (HS). Treatment with chondroitinase has little effect on the non-permissive properties of M glia but reduces the growth-supporting ability of L glia. By contrast, heparitinase I produces no significant changes on L glia but leads to neurite growth promotion by M glia. Taken together, these results suggest that glial CS helps to promote neurite growth and, more importantly, they indicate that a HS proteoglycan is, at least, partially responsible for the non-permissive role of the midline glia to the growth of midbrain neurites.
Garcia-Abreu
J
J
Departamento de Anatomia, Instituto de Ciências Biomédicas, Rio de Janeiro, Brazil.
Mendes
F A
FA
Onofre
G R
GR
De Freitas
M S
MS
Silva
L C
LC
Moura Neto
V
V
Cavalcante
L A
LA
D000818:Animals; D001253:Astrocytes / Q000378:metabolism / Q000502:physiology; D002478:Cells, Cultured; D004622:Embryo, Mammalian; D005353:Fibronectins / Q000378:metabolism; D005904:Glial Fibrillary Acidic Protein / Q000378:metabolism; D006025:Glycosaminoglycans / Q000378:metabolism; D006497:Heparan Sulfate / Q000502:physiology*; D015151:Immunoblotting; D007797:Laminin / Q000378:metabolism; D008636:Mesencephalon / Q000166:cytology / Q000502:physiology*; D051379:Mice; D016501:Neurites / Q000502:physiology*; D009457:Neuroglia / Q000502:physiology*; D019063:Tenascin / Q000378:metabolism
D005353:Fibronectins; D005904:Glial Fibrillary Acidic Protein; D006025:Glycosaminoglycans; D006497:Heparan Sulfate; D007797:Laminin; D019063:Tenascin