Enables DNA-binding transcription repressor activity, RNA polymerase II-specific; identical protein binding activity; and sequence-specific DNA binding activity. Involved in several processes, including circulatory system development; regulation of gene expression; and umbilical cord morphogenesis. Acts upstream of or within several processes, including animal organ development; blood vessel development; and osteoblast development. Located in cytoplasm and nucleus. Is expressed in several structures, including cardiovascular system; central nervous system; genitourinary system; jaw; and sensory organ. Orthologous to human HEY1 (hes related family bHLH transcription factor with YRPW motif 1). [provided by Alliance of Genome Resources, Apr 2022]