Binding Patterns of Lectins with GalNAc specificity in the mouse dorsal root ganglia and spinal cord

To localize membrane glycoconjugates in neurons of the mouse spinal cord an d 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 l ectins, the majority of them recognizing N-acetyl-D-galactosamine (GalNAc) terminal sugar residues. In the dorsal root ganglia of PO animals, the diff erent lectins showed distinct patterns of labeling in either cells of the n ervous system, including neurons, or other structures such as nerves or blo od vessels. Moreover, some of these lectins showed important changes in the ir pattern of labeling during postnatal development. This was especially re levant for lectins that label a subpopulation of small-sized cells that hav e been previously identified as the nociceptive cells of the DRG. Enzymatic digestion of sections with neuraminidase removes sialic acid from the carb ohydrate chains of glycoconjugates thus exposing novel sugar residues. When this treatment was applied to DRG sections from postnatal animals the patt ern of lectin staining was either changed or eliminated and heterogeneous s ubsets of glycoconjugates normally masked by this sugar were exposed. In th e spinal cord of PO animals, none of the lectins labeled cells in the centr al gray matter. However, after the enzymatic digestion of sections with neu raminidase, spinal cord motoneurons and some other cells were labeled by tw o of the lectins suggesting that GalNAc residues present in these cells are normally masked by terminal sialic acid. Altogether, these results show im portant changes in the temporal and spatial expression of glycoconjugates t hat may be relevant for the postnatal development of the CNS and PNS of mic e.