Figure 1. FAK expression and phosphorylation during development.

(A) Western Blots from extracts of equal numbers of embryos probed with a monoclonal antibody against the C-terminus of FAK or polyclonal antibodies against the phosphorylated tyrosine residues indicated. FAK is phosphorylated on all three residues both before and after gastrulation. The intensity values from the densitometry analysis of the western blots were normalized against total FAK amount. (B) Blastula (1^st column), early gastrula (2^nd column) and late gastrula embryos (3^rd column) stained with P-Y397, P-Y576, P-Y861 and P-Y31paxillin antibodies as indicated. Phosphorylated FAK and paxillin can be detected on the plasma membrane from early blastula stages including the apical region of superficial blastomeres. During gastrulation elevated levels of phosphorylation are detected in the highly morphogenetic mesodermal tissues (white arrowheads). Scale bar: 400 µm.