Fig. 8. Combinatorial actions of patterning and proneural/inhibitory HLH factors in specifying neuronal and glial cell lineages. The activities of individual transcription factors (patterning factors, left; proneural/inhibitory HLH factors, top) and their combinations are summarized. Arrows and blunt-ended lines indicate stimulation and inhibition, respectively, of differentiation into specific cell types. The thickness of each arrow arbitrarily reflects the strength of the activity. Olig, oligodendrocyte.