Cloning and characterization of focal adhesion kinases and their roles in zebrafish embryonic development

Focal adhesion kinase (FAK) is a protein tyrosine kinase involved in cell migration, proliferation and cell adhesion. To investigate the role of FAK in embryonic development, we employed a well-established vertebrate model, zebrafish, to proceed genetic study of FAK in vivo. Here we isolated two zebrafish FAK genes, fak1a (3159 bp) and fak1b (3138) bp and expressed in FAK-/- and NIH3T3 mammalian cells to study the outcomes of cell biology, biochemistry and cellular functional level in comparison to those of mouse FAK. Zebrafish fak1a and fak1b showed more than 85% similarity in amino acid sequences to their homologs in chicken, mice and humans. The expression of fak1a could promote cell proliferation, migration, and motility. In addition, we used antisense morpholino oligos (MO) knocking down intrinsic fak1a and fak1b in zebrafish embryos to investigate the role of Fak1a/1b during development. Upon knocking down intrinsic fak1a and fak1b in zebrafish embryos, epiboly and convergence extension defects were prominent. By a means of time-lapse recording assay, we demonstrated that zebrafish fak governed convergent extension movements via regulating cell migration ability and polarization. Also, the expression of eve1 is down regulated upon knocking down fak1a, suggesting that Fak1a may play a role in anterior-posterior (A-P) axial patterning. Together, zebrafish Faks involved in regulating cell migration both in vitro and in vivo, it is been regarded as the driving force during gastrulation cell movement which contributes to normal mesoderm formation.