Transcriptional activator. Expressed both maternally and zygotically. Distributed throughout the blastoderm at the blastua stage but becomes confined to the future ectoderm by the shield stage. Expressed in the presumptive neuroectoderm at the 75-80% epiboly stage. From the tail bud to the 3-somite stage, expressed throughout the neural plate, except in the anterior margin. At the 12- to 25-somite stage, expressed broadly in the central nervous system.