Identification and expression patterns of members of the protease-activated receptor (PAR) gene family during zebrafish development.

Protease-activated receptors (PARs) play critical roles in hemostasis in vertebrates including zebrafish. However, the zebrafish gene classification appears to be complex, and the expression patterns of par genes are not established. Based on analyses of genomic organization, phylogenetics, protein primary structure, and protein internalization, we report the identification of four zebrafish PARs: par1, par2a, par2b, and par3. This classification differs from one reported previously. We also show that these genes have distinct spatiotemporal expression profiles in embryos and larvae, with par1, par2a, and par2b expressed maternally and ubiquitously during gastrula stages and their expression patterns refined at later stages, and par3 expressed only in 3-day-old larvae. Notably, the expression patterns of zebrafish par1 and par2b resemble those of their mammalian counterparts, suggesting that receptor function is conserved among vertebrates. This conservation is supported by our findings that Par1 and Par2b are internalized following exposure to thrombin and trypsin, respectively.