DETECTION OF MESSENGER-RNA TRANSCRIPTS FOR RETINOIC ACID, VITAMIN-D3, AND THYROID-HORMONE (C-ERB-A) NUCLEAR RECEPTORS IN HUMAN SKIN USING REVERSE TRANSCRIPTION AND POLYMERASE CHAIN-REACTION

Differentiation of keratinocytes involves both non-genomic and genomic events. The genomic effects are regulated by ligand-dependent transcription factors, e.g. the steroid/thyroid super-family of nuclear receptors. In the present study we examined mRNA expression of receptors for retinoic acid, thyroid hormone, and vitamin D3 in normal human skin and cultured keratinocytes using reverse transcription coupled to the polymerase chain reaction. The vitamin D3 receptor and the retinoic acid receptor (RAR) gamma together with the more distantly related RXRalpha were amplified extensively in skin and cultured keratinocytes. RARalpha was amplified at a lower level, and RARbeta was almost undetectable. The thyroid hormone receptors alpha1 and beta1 were weakly amplified, but to comparable levels. Because receptors for retinoic acid, thyroid hormones, and vitamin D3 are all expressed in human epidermis differentiation of keratinocytes is probably regulated at transcriptional level by these molecules. It remains to be seen whether alterations in the expression of the nuclear receptors occur in certain skin disorders.