Transcriptional activator involved in the development of insulin-producting beta cells in the endocrine pancreas (By similarity). May also be involved in specifying diencephalic neuromeric boundaries, and in controlling the expression of genes that play a role in axonal guidance. Binds to elements within the NEUROD1 promoter (By similarity). Expressed in a continuous narrow band of cells along a boundary zone demarcating the location at which two of the earliest nuclei in the brain differentiate. Belongs to the NK-2 homeobox family.