| Cutaneous malignant melanoma is a tumour derived from melanocytes. Although this cancer tends to metastasize, tumours at early stages are often curable by surgical excision alone. Melanoma genetics research aims to identify variants that predispose individuals and families to the disease, thereby allowing routine surveillance and early detection of tumours.; Germline mutations in the coding region of CDKN2A (chromosome 9p21) account for susceptibility in 25-40% of melanoma kindreds, and I hypothesized that mutations that affect splicing may also play a role. I helped characterize three splice donor sites variants that lead to aberrant splicing within the exons, thereby eliminating parts of sequences that encode the functional domain of the p16INK4a, tumour suppressor. I also used RT-PCR to detect aberrantly spliced products resulted from intronic mutations. Though I found no such phenomenon in 15 melanoma probands, I uncovered a mutation (IVS2-284A>G) in the affected members of a large American melanoma kindred. This mutation generates an aberrant splice acceptor site, resulting in transcripts that include 196 bp of intronic sequence.; Although epidemiological data suggest the presence of a genetic basis to melanoma in the Ashkenazi Jews, no disease-associated mutations have been found in this population. I did not find any such variants in CDKN2A and CDK4, the two genes known to contain predisposition mutations. I also excluded associations between melanoma and chromosomes 9p21 or 1p22, the confirmed and proposed melanoma susceptibility loci.; Then, I searched for associations between melanoma and variants in the melanocortin-1 receptor gene (MC1R) in the Ashkenazim. MC1R, a G-protein coupled receptor (GPCR), regulates melanin balance and melanocyte growth and differentiation through cAMP signal transduction. I found that the R142H variant in MC1R was significantly associated with melanoma (p = 0.024). The Arginine-142 residue is almost 100% conserved across all known GPCRs, and a previous biochemical study had found that MC1R bearing R142H lead to decreased production of CAMP.; The characterization of the splice site variants, the discovery of the intronic mutation in CDKN2A, and the findings on the R142H weak modifier variant of MC1R should allow the identification of additional at risk individuals and families. |
