ONTOGENY, CHARACTERIZATION AND TROPHIC DEPENDENCE OF AC4/ANTI-SSEA-1-POSITIVE SENSORY NEURONS IN THE CHICK

Antibodies to a variety of carbohydrate differentiation antigens were screened in dorsal root ganglia (DRG) of hatchling chicks with the goal of identifying markers for subpopulations of sensory neurons. Two antibodies, AC4 and anti-SSEA-1, which recognize a lactoseries glycoconjugate(s), labeled a subset of small and medium diameter neurons in the dorsomedial DRG. This antigen was present early in embryonic development, being expressed on sensory neuron precursors prior to their withdrawal from the cell cycle, and appeared to be associated with a cell-surface glycolipid. Immunoreactive neurons were supported in vitro primarily by brain-derived neurotrophic factor (BDNF), to a lesser extent by neurotrophin-3 (NT-3), but not by nerve growth factor (NGF). The subpopulation of sensory neurons identified by these antibodies is likely to be functionally diverse, having targets in both skin and muscle.