The Zic family is a group of genes encoding zinc finger proteins that are highly expressed in the mammalian cerebellum. Zic genes are the vertebrate homologue of Drosophila pair-rule gene, odd-paired(opa), which plays important roles in the parasegmental subdivision as well as in the visceral mesoderm development of Drosophila embryos. Recent studies on human, mouse, frog, fish and ascidian Zic homologues support that Zic genes are involved in a variety of developmental processes, including neurogenesis, myogenesis, skeletal patterning, and left-right axis establishment. In an effort to explore possible functions of Zic proteins during vertebrate embryogenesis, we initially examined more detailed expression pattern of zebrafish homologue of zic3(zic3z). zic3z transcripts are detected in the neuroectoderm, neural plate, dorsal neural tube, and brain regions including eye field during early embryonic development. Marker DNA studies found that zic3z transcription is modulated by BMP, Wnt, and Nodal signals particularly in the dorsal and vegetal neuroectoderm at gastrula. Interfering with zic3z translation with zic3z-specific morpholino causes abnormal brain formation and expansion of the optic stalk cells. Retinal ganglion cells(RGCs) undergo abnormal neuronal differentiation. These findings suggest that zic3z defines the dorsal and vegetal neuroectoderm to specify brain formation and retinal neurogenesis during early embryonic development.