RPE cells express DDC but not DAT. (A) DDC from RPE cells was detected by western blot. RPE protein was loaded and the equal level of C57 mouse striatum protein was used as positive control; protein DDC was detected by western blot and both samples displayed the same size protein bands. The protein DAT could not be detected in RPE cells. (B) The cDNA of DDC but not DAT was detected by PCR from the total cDNA of RPE cells.