QUALITATIVE AND QUANTITATIVE CATALOG OF TYROSINASE ALTERNATIVE TRANSCRIPTS IN NORMAL MURINE SKIN MELANOCYTES AS A BASIS FOR DETECTING MELANOMA-SPECIFIC CHANGES

The decline in cell differentiation commonly associated with malignant progression may be due in part to an increase in alternative splicing of the pre-mRNAs of tissue-specific genes. As a necessary basis for i nvestigating this possibility in a murine model of cutaneous melanoma, the complete qualitative and quantitative inventory of alternative tr anscripts was sought for the tyrosinase gene in normal mouse skin mela nocytes, as this gene plays a key role in melanization. Of 111 alterna tive mRNAs predicted from known splice sites in the gene, 19 isoforms were detected, and their abundances determined, through a systematized protocol involving splice junction-specific probes, exon-specific res triction enzymes, and quantitative RT-PCR with an RNA internal standar d, No unpredicted tyrosinase transcripts were discovered. Two of the t ranscripts, each involving an intra-exonic deletion and present at rel atively low abundance in normal skin, were subsequently found to be co nsistently upregulated in melanomas. (C) 1997 Academic Press.