JAK1 KINASE IS REQUIRED FOR CELL MIGRATIONS AND ANTERIOR SPECIFICATION IN ZEBRAFISH EMBRYOS

Establishment of the vertebrate body plan requires a variety of signal ing molecules. In a search for tyrosine kinases expressed in early zeb rafish embryos, a model system for the study of vertebrate development , we discovered Jak1 kinase to be maternally encoded and the mRNA even ly distributed among the cells of blastula-stage embryos. Injection of RNA-encoding dominant-negative Jak1 kinases reduces a specific cell m igration, epiboly, and results in the reduction of goosecoid expressio n and of anterior structures. This work establishes that. In addition to its role in signal transduction of cytokines in adult tissues, Jak1 kinase has a role in early vertebrate development.