Content area
Full Text
Summary
To localize membrane glycoconjugates in neurons of the mouse spinal cord and dorsal root ganglia (DRG), cryostat sections of newborn (PO), 7 day-old (P7), P14, P21 and P31 animals were stained with ten FITC-conjugated plant lectins, the majority of them recognizing N-acetyl-D-galactosamine (GalNAc) terminal sugar residues. In the dorsal root ganglia of PO animals, the different lectins showed distinct patterns of labeling in either cells of the nervous system, including neurons, or other structures such as nerves or blood vessels. Moreover, some of these lectins showed important changes in their pattern of labeling during postnatal development. This was especially relevant for lectins that label a subpopulation of small-sized cells that have been previously identified as the nociceptive cells of the DRG. Enzymatic digestion of sections with neuraminidase removes sialic acid from the carbohydrate chains of glycoconjugates thus exposing novel sugar residues. When this treatment was applied to DRG sections from postnatal animals the pattern of lectin staining was either changed or eliminated and heterogeneous subsets of glycoconjugates normally masked by this sugar were exposed. In the spinal cord of PO animals, none of the lectins labeled cells in the central gray matter. However, after the enzymatic digestion of sections with neuraminidase, spinal cord motoneurons and some other cells were labeled by two of the lectins suggesting that GalNAc residues present in these cells are normally masked by terminal sialic acid. Altogether, these results show important changes in the temporal and spatial expression of glycoconjugates that may be relevant for the postnatal development of the CNS and PNS of mice.
Introduction
Cell surface carbohydrates are likely to play important roles in the development of the nervous system (see for review Margolis & Margolis, 1979; Jessell et al., 1990). It has been shown that in brain, membrane associated glycoproteins constitute 85-90% of total glycoprotein content (Margolis & Margolis, 1979). Lectins are useful tools to study membrane glycoproteins since they are proteins or glycoproteins that bind with high affinity to specific carbohydrate residues (see for a general review Ponder, 1983; Jessell et al., 1990). In the nervous system, the use of lectins has been proven to be an effective approach to study the functional relevance of glycoconjugates. For example, several reports have described the existence...