The role of cyclops/nodal signaling in zebrafish early embryogenesis

Abstract

Nodal proteins are members of the transforming growth factor-beta (TGF-b) family and have crucial roles in mesendoderm formation and left-right patterning during vertebrate development. We isolated a temperature-sensitive mutation affecting the zebrafish Nodal-related secreted signaling factor, Cyclops. I use this mutant allele, cycsg1, to answer a central question pertaining to the timing of vertebrate floor plate specification. I found that the floor plate in zebrafish is specified early in development, during gastrulation. I also revealed that the mechanism of the temperature-sensitive phenotype which caused by a premature stop codon in the pro-domain in cyclops gene is due to a readthrough but it is not stop-codon dependent. By detailed analysis in pro-domain of Cyclops, I found sequences important for protein activity, critical amino acid for inhibitor binding, and an important region responsible for the signaling range of Cyclops.