Fertilization triggers activation of Fyn kinase in the zebrafish egg

Fertilization results in the tyrosine phosphorylation of several egg proteins and studies have shown that tyrosine protein kinase activity is required for successful fertilization. The Fyn protein kinase has been detected in eggs of the sea urchin, frog and rat, although measurement of fertilization-induced changes in Fyn kinase activity have only been successful in the sea urchin system. The present study demonstrates the presence of Fyn kinase in the zebrafish egg and the stimulation of this enzyme at fertilization. Activation of Fyn was detected as early as 30 seconds post-fertilization and increased approximately six-fold by 2 minutes post-insemination. The activation of Fyn in the zebrafish egg required sperm and was not observed in spontaneously activated eggs.