IDENTIFICATION AND SEQUENCING OF A PUTATIVE VARIANT OF PROOPIOMELANOCORTIN IN HUMAN EPIDERMIS AND EPIDERMAL-CELLS IN CULTURE

Proopiomelanocortin (POMC) is a precursor polypeptide for various bioa ctive peptides, including adrenocorticotropic hormone, alpha-, beta-, and gamma-melanotropin, beta-endorphin, and beta-lipotropin. Although the classical source of POMC is the pituitary, various studies indicat e the expression of POMC in several nonpituitary tissues. In this stud y, in situ hybridization with anti-sense cRNA riboprobe was used to sh ow expression of POMC mRNA in human epidermis and cultured human epide rmal cells (melanocytes and keratinocytes). POMC mRNA was amplified by reverse transcriptase-polymerase chain reaction using anti-sense and sense primers designed from Exons 2 and 3 of POMC gene. A approximate to 300 bp product was present in normal human skin, grafted human skin , and cultured normal human melanocytes and keratinocytes. By Southern analysis this product was hybridized specifically to the POMC cDNA. S equence analysis of the reverse transcriptase polymerase chain reactio n product from tissues or cells showed 85% homology to POMC cDNA from human, bovine, pig, and monkey sources. This suggests the existence of a putative isoform or variant of POMC mRNA in human epidermis.