Transcriptional repressor. Dimerization is required for DNA-binding (By similarity). Isoform a, but not isoform b, interacts with ctbp1. All isoforms show similar spatial expression. Localized to the animal hemisphere of early cleavage stage embryos. At tailbud stages, expressed in regions of the brain, eye and the splanchnic mesodermal layer of the lateral plate mesoderm surrounding the gut. At stage 35, expressed within the lens of the eye, in distinct regions of the head mesenchyme and in the area anterior to the gut. In the brain the anterior-most expression is restricted to the outer region of the mesencephalon. With ongoing development, additional expression is found in the curling gut. Isoform a and isoform b are expressed both maternally and zygotically. Maternal expression disappears before gastrulation and zygotic expression begins after stage 20 and continues throughout embryogenesis. In contrast, isoform c is only detected from stage 30. The leucine-zipper is required for dimerization and transcriptional repression.