The D1.1 antigen: a cell surface marker for germinal cells of the central nervous system

A monoclonal antibody against a cell surface ganglioside present on neuroepithelial cells was produced by immunizing mice with the B49 cell line, a clonal line with properties of both neurons and glial cells. The expression of this antigen, designated as D1.1, was analyzed in the developing rat cerebellum. The D1.1 antigen was localized by the immunofluorescent staining method to germinal cells of the external granule layer (EGL). Fluorescent labeling of cells comprising the EGL was apparent on embryonic day 18 when the EGL first forms, and the labeling was present throughout the period of postnatal cerebellar development. No cells within the adult cerebellum were labeled with the anti-D1.1 antibody. The D1.1-labeled cells of the EGL synthesize DNA, as demonstrated by [3H] thymidine autoradiography. However, within 48 hr after their final mitosis, nascent cerebellar cells that had migrated away from the external granule layer were no longer labeled with antibody. Some of the neurons and some of the astrocytes in cerebellar cell cultures were fluorescently labeled with the anti-D1.1 antibody. The number of anti-D1.1-labeled neurons in the cultures decreased over the first 10 days in vitro in agreement with the findings that in vivo the fluorescent labeling of the D1.1 antigen disappears from postmitotic cells. The antibody recognizes a ganglioside that in thin layer chromatographic experiments has a mobility between that of the GM1 and GM2 ganglioside. These data suggest that the D1.1 ganglioside antigen is a cell surface marker for germinal cells and that the acquisition and subsequent loss of this antigen is an aspect of the biochemical maturation of neurons and glial cells.