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Characterization and Distribution of a New Cell Surface Marker of Neuronal Precursors

In a screen for novel cell surface markers of neuronal progenitors, we recently identified mAb 2F7 that recognizes an epitope present on both progenitor cells and postmitotic neurons, in the developing CNS and PNS. In the embryonic rat telencephalon, the mAb 2F7 epitope is expressed by migratory and postmigratory neurons in the developing cerebral cortex, as well as by presumptive neuronal progenitor cells of the ventricular zone. In the neonatal forebrain mAb 2F7 labels postmitotic neurons, including those of the developing cerebral cortex and olfactory bulb, as well as the axons of the corpus callosum. While mAb 2F7 immunoreactivity is present on only a low density of the neuronal progenitor cells situated in the anterior part of the subventricular zone, a progressively higher proportion of cells forming the rostral migratory stream express this epitope. mAb 2F7 labels the surfaces of neurons and neuronal precursors, but not mature oligodendrocytes and astrocytes in primary cultures derived from the rat neural tube. In vivo, migrating neural crest cells, motor neurons, and axonal projections associated with the spinal cord express the mAb 2F7 epitope. Immunoblot analyses reveal that the mAb 2F7 epitope resides on several high-molecular-weight, membrane-associated proteins, and is likely to be composed of N-linked carbohydrate. These findings suggest that mAb 2F7 recognizes a novel epitope that is present on progenitor cells and postmitotic, differentiating neurons in the developing mammalian nervous system.