Protooncogene expression identifies a transient columnar organization of the forebrain within the late embryonic ventricular zone.

Immunocytochemical studies using monoclonal antibodies directed against oncogenic peptides revealed a heterogeneous distribution of the peptides within the ventricular zone of the embryonic day 18 rat forebrain. The sis-, src-, ras-, and myc-encoded peptides were concentrated in the same isolated clusters of 5-25 radial glial cells (also identified by vimentin staining), providing a transient columnar compartmentalization to the ventricular zone. An increased number of [3H]thymidine-labeled ventricular zone cells were observed within the protooncogene stained radial glial cell columns as compared to noncolumn areas. The columnar heterogeneity of radial glial cells reveals the mosaicism of the embryonic ventricular zone and the differential proliferation of its cells.