Abstract
Cell surface carbohydrates are thought to play important roles in the development and differentiation of mammalian cells. In previous studies we have found that one population of dorsal root ganglion (DRG) neurons is specified by the expression of complex globoseries oligosaccharides (Dodd, J., D. Solter, and T. M. Jessell (1984) Nature 311: 469–472; Jessell, T. M., and J. Dodd (1985) Philos. Trans. R. Soc. Lond. (Biol.) 308: 271–281). We now report that monoclonal antibodies (MAbs) directed against backbone structures of lactoseries oligosaccharides define antigens present in the cytoplasm of a second, anatomically and functionally distinct subset of DRG neurons. Lactoseries carbohydrate structures identified by MAb A5 are restricted to small- and intermediate-diameter DRG neurons with central projections in the superficial dorsal horn of the rat spinal cord. The distribution of labeled terminals suggests that many of the DRG neurons that express lactoseries carbohydrates are likely to convey nociceptive information. More complex galactose- and fucose-substituted lactoseries structures recognized by MAbs LD2, KH10, TC6, TD10, LA4, and anti-Lewis a are segregated on subsets of DRG neurons that differ in their expression of substance P, somatostatin, and fluoride-resistant acid phosphatase and in their laminar termination in the superficial dorsal horn. The majority of lactoseries carbohydrate antigens identified in the cytoplasm of DRG neurons are also expressed on the surface of subsets of DRG neurons in culture. These studies establish that structurally defined carbohydrate differentiation antigens specify the majority of primary sensory neurons with cutaneous receptive fields. Moreover, lactoseries carbohydrate structures similar or identical to those expressed on neonatal DRG neurons in culture have been implicated in cell-cell interactions at early stages of preimplantation embryonic development. Our observations suggest strategies for testing the hypothesis that carbohydrates present on the surface of subsets of DRG neurons play a role in cell interactions that contribute to the laminar organization of sensory afferents in the developing spinal cord.