The long-term objectives are to establish a basic linkage map of the genome of the laboratory marsupial, Monodelphis domestica, and, thereby to increase the scientific value of this animal model in a variety of basic and applied research situations. The establishment of this gene map (the first for any marsupial) would enable the localization of genes that contribute to physiologically relevant variation in complex characteristics such as developmental anomalies and disease susceptibilities, and would provide additional insights regarding the evolution of the mammalian genome, particularly the conservation of gene syntony and linkage organization between Monodelphis and humans. This knowledge would facilitate the chromosomal localization and subsequent identification and molecular characterization of genes in the human genome that are possible homologs of genes that become identified as disease-related factors in the Monodelphis model. Our immediate plans are to utilize the gene map to identify associations between alleles at candidate tumor suppressor and oncogene loci and the occurrence of ultraviolet radiation-induced skin and eye neoplasia (melanocytic nevus, melanoma, and corneal sarcoma) that will be studied in Projects 1,2, and 3 of this Program Project. In the future we intend to use the map in concert with information generated in Projects 4 and 5 concerning the inheritance of variation in cholesterol metabolism, to localize and identify genes that affect differential lipemic responsiveness to high fat, high cholesterol dietary challenge. For the current project period, our aims are: 1) to generate a """"""""framework map"""""""" composed of a minimum of 100 anonymous polymorphic DN marker sequences (using RAPD-PCR technology) in the Monodelphis genome, 2) to identify (via Southern blot/RFLP analysis) genetic polymorphisms among marsupial homologs of human tumor suppressor genes (APC, DCC, MCC, NF, p53, RB, WT) and ras family oncogenes (H-ras, K-ras, N-ras), 3) to establish the identities of linked gene clusters involving RAPD, tumor suppressor, oncogene, and (previously identified) isozyme loci via recombination analysis in multiply heterozygous female Monodelphis (which exhibit low recombination rates), 4) to initiate studies of gene order and linkage distances among synthetic marker loci using recombination data from multiply heterozygous males (which exhibit high recombination rates), 5) to identify associations between neoplastic phenotypes and particular alleles at tumor suppressor gene and oncogene loci, 6) to determine whether loss of heterozygosity (LOH) occurs at selected tumor suppressor loci in cultured cells derived from melanomas and corneal sarcomas of this species.
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