REGIONALIZATION OF THE DEVELOPING FOREBRAIN - A COMPARISON OF FORSE-1, DLX-2, AND BF-1

The FORSE-1 monoclonal antibody (mAb) was generated using a strategy d esigned to produce mAbs against neuronal cell surface antigens that mi ght be regulated by regionally restricted transcription factors in the developing CNS. To determine whether FORSE-1 has a labeling pattern s imilar to that of known transcription factors, the expression of BF-1 and Dlx-2 was examined by in situ hybridization on sections serial to those labeled with FORSE-1. We find a striking overlap between BF-1 an d FORSE-1 in the telencephalon; both are expressed in the lateral but not the medial walls of the telencephalon, and the boundaries of expre ssion are apparently identical. FORSE-1 staining is detected prior to BF-1 expression in the neural tube, however. FORSE-1 and Dlx-2 have ve ry different patterns of expression in the forebrain, suggesting that regulation by Dlx-2 cannot by itself explain the distribution of FORSE -1. However, they share some sharp boundaries in the diencephalon. In addition, FORSE-1 identifies some previously unknown boundaries in the developing forebrain. These results indicate that a new cell surface marker can be used to subdivide the embryonic telencephalon and dience phalon into regions smaller than previously described, providing neces sary complexity to the developmental patterning in the forebrain.