Human and canine mRNA expression evaluated by RT-PCR. Expression of tyrosinase mRNA by human (SK-MEL-188) and canine (CML 83-2) melanoma cell lines was examined by RT-PCR. Conserved, tyrosinase-specific primer sets, 3/4 and 3/5 (schematic diagram), were used to amplify a 528 bp and an overlapping 918 bp cDNA fragment, respectively, indicating the expression of tyrosinase genes in both cell lines.