Fig. 4. The combinatorial activity of patterning proteins and proneural proteins promotes neural cell type commitment. The combinatorial activities of patterning proteins (vertical axis) and of proneural proteins and inhibitory HLH proteins (horizontal axis) in the commitment of progenitor cells to neuronal (N), oligodendroglial (O) or astroglial (A) fates are shown as entries on a matrix. These results were obtained by overexpressing combinations of factors in neural stem cell population cultures derived from rat embryonic spinal cord. The effect of particular transcription factor combinations on the generation of the primary neural cell types is represented by `+' for significant induction, `-' for significant repression and `0' for no activity. See text and Sugimori et al. (Sugimori et al., 2007) for details.