A neural-specific transcription factor that can act as both a transcriptional activator and a transcriptional repressor. Both represses and activates neuronal differentiation in a dose-dependent manner, independently regulating cell fate choice and cell proliferation. Converts ectoderm to a neural fate. Suppresses the transcription of the cell cycle inhibitor p27xic1 and promotes the proliferation of neuroectodermal cells at a high concentration. Promotes the transcription of p27xic1 and inhibits ectodermal proliferation at low concentrations. The transcription factors foxd1 and foxg1 mutually repress each other to pattern the forebrain. At late gastrula and early neurula stages, expressed in a narrow stripe at the anterior end of the neural plate. At later stages, this stripe of expression thickens and expression also appears in the lateral margin of the neural plate. The anterior line differentiates to show expression in the forebrain, anterior (nasal) retina and olfactory placode, whereas the lateral cells form neural crest cells that migrate in the first branchial arch. In tailbud stages and tadpoles, expressed primarily in the neuroepithelial cells of the telencephalon.