Role of 14-3-3 proteins in early Xenopus development.

14-3-3 proteins are intracellular dimeric phosphoserine/threonine-binding molecules that participate in signal transduction and checkpoint control pathways. 14-3-3 proteins are required for normal eye development, brain function, and terminal patterning in Drosophila melanogaster, but the role of 14-3-3 proteins in vertebrate development is undefined. In this work an unphosphorylated peptide inhibitor of 14-3-3, R18, was used to determine the role of 14-3-3 proteins in Xenopus embryonic development. Biochemical analysis demonstrated that R18 was specific and efficient at attenuating global 14-3-3 activities in Xenopus embryos. Microinjection experiments showed a requirement for 14-3-3 function in mesodermal specification. Inhibition of 14-3-3 resulted in embryos with axial patterning defects and reduced expression of mesodermal marker genes. These phenotypic defects were caused by impaired fibroblast growth factor signaling in R18-injected embryos. These results establish the importance of 14-3-3 proteins in vertebrate embryonic development.