CYCLOPS ENCODES A NODAL-RELATED FACTOR INVOLVED IN MIDLINE SIGNALING

Ventral structures in the central nervous system are patterned by sign als emanating from the underlying mesoderm as well as originating with in the neuroectoderm. Mutations in the zebrafish, Danio rerio, are pro ving instrumental in dissecting these midline signals. The cyclops mut ation leads to a loss of medial floor plate and to severe deficits in ventral forebrain development, leading to cyclopia. Here, we report th at the cyclops locus encodes the nodal-related protein Ndr2, a member of the transforming growth factor type beta superfamily of factors. Th e evidence includes identification of a missense mutation in the initi ation codon and rescue of the cyclops phenotype by expression of ndr2 RNA, here renamed ''cyclops.'' Thus, in interaction with other molecul es implicated in these processes such as sonic hedgehog and one-eyed-p inhead, cyclops is required for ventral midline patterning of the embr yonic central nervous system.