Our microarray and in situ hybridization analyses of this zebrafish HEP model revealed downregulation of six peptidase precursor genes – including carboxypeptidase A5 (cpa5), chymotrypsinogen 1 like (ctr1l), chymotrypsinogen B1 (ctrb1), elastase 2 like (ela2l), trypsin precursor (try) and trypsin like (tryl) – specifically in the exocrine pancreas of the HEP zebrafish (yquem/urod, −/−) (Wang et al., 2007). This evidence concerns the gene CTRB1 and hepatoerythropoietic porphyria.