Transcription of Melanogenesis Enzymes in Melanocytes: Dependence upon Culture Conditions and Co‐Cultivation With Keratinocytes

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Abstract
Eumelanogenesis of human skin melanocytes requires at least three enzymes: tyrosinase, TRP 1, and TRP 2. The regulation of these enzymes on transcriptional level was detected in a semiquantitative attempt. The total RNA of melanocytes was reverse‐transcripted and followed by a PCR with degenerated primers for all three enzymes. The amplification products were related to each other densitometrically. We examined five different culture conditions: 1) melanocytes in a popular phorbolester containing F‐10‐medium, 2) melanocytes in a co‐culture medium with EGF, 3) melanocytes in a co‐culture medium with high calcium, 4) melanocytes co‐cultured with keratinocytes in EGF containing co‐culture medium, and 5) melanocytes co‐cultured with keratinocytes in co‐culture medium with high calcium. Melanocytes cultured in phorbolester containing F‐10‐medium featured transcripts of tyrosinase, TRP 1, and TRP 2 in the ratio 45:45:10. The same results were obtained for melanocytes co‐cultured with keratinocytes under the two different culture conditions. In melanocytes cultured alone in co‐culture media only TRP 1‐transcripts were present. It is likely that under co‐culture conditions a keratinocyte‐derived factor supports the transcription of all three enzymes. For melanocytes in the phorbolester‐containing melanocyte medium a proteinkinase C dependent regulation of transcription seems possible.