Transcriptional activator which is essential for neuronal differentiation. Can promote ectotopic neuronal differentiation and confers insensitivity to lateral inhibition, but only in cooperation with bHLH transcription factors. First expressed at mid-late gastrulation within the dorsal ectoderm. By the completion of gastrulation its expression is clearly restricted to 3 groups of cells arranged in a radially symmetrical pattern on either side of the dorsal midline of the posterior neural plate, where the ventral, intermediate and dorsal groups of cells differentiate into motor neurons, interneurons and sensory neurons respectively. The same pattern of expression is maintained in later-stage neurula embryos. Positively regulated by X-NGNR-1 and negatively regulated by lateral inhibition. Belongs to the MYT1 family.