In this study, we show the feasibility of this approach and provide evidence that the genes identified by the bioinformatics method, c- Myc and Cdc25A, are strong candidates for the tumor latency modifiers Apmt1 and Apmt2. In an attempt to circumvent this process, we therefore developed a combined genetics, genomics, and bioinformatics approach to identify interesting candidate genes for analysis and testing. This method, although effective, is slow and laborious, entailing significant time, animal costs, and effort.
#Jessica subler series#
The conventional strategy for identification of modifier or QTL candidate genes requires the creation of congenic animals, followed by mapping the trait in question in a series of subcongenic intervals. Backcross analysis showed the presence of two epistatically interacting loci on Chrs 9 and 15 ( LeVoyer et al., 2000) and generation of congenic animals for high-resolution conventional quantitative trait analysis initiated (J. Previously, we have shown by outcrossing to the I/LnJ inbred strain of mice, the presence of epistatically interacting latency modifiers in the I/LnJ genome that significantly accelerate tumor appearance ( Lifsted et al., 1998). These animals express the mouse polyoma Middle-T antigen (PyVT) from a mouse mammary tumor virus enhancer and promoter, resulting in the development of synchronous, multifocal tumors by 57 days of age on average ( Guy et al., 1992 Lifsted et al., 1998).
To study these genetic factors, our laboratory uses a transgenic mouse mammary tumor model, the FVB/N-TgN(MMTV-PyVT) 634Mul mouse ( Guy et al., 1992). Identification and characterization of these additional genetic factors will hopefully lead to a greater understanding of the etiology of breast cancer and potentially novel ways to prevent or treat it. Although environmental exposures are likely to account for some of the variability, there is evidence that there may be additional genetic elements that contribute to the differential expressivity of the phenotype ( Krontiris et al., 1993 Ford and Easton, 1995 Phelan et al., 1996 Kristensen et al., 1998). However, women carrying the same mutation, even within families, can exhibit significantly different clinical expression ( Goldgar et al., 1994 Friedman et al., 1995 Langston et al., 1996 Easton et al., 1997), with some women developing cancer early in life, whereas others remain unaffected until >70 years of age ( Narod et al., 1995). Women carrying mutations in the breast cancer susceptibility genes BRCA1 and BRCA2 are highly predisposed to developing cancer compared with the general population. These data suggest that c- Myc and Cdc25A are Apmt1 and Apmt2, and suggest that, at least in certain instances, bioinformatics can be utilized to bypass congenic construction and subsequent mapping in conventional QTL studies. In vivo analysis was performed by generating compound PyVT/ Myc double-transgenic animals to mimic the hypothetical model, and was found to recapitulate the age-of-onset phenotype. Molecular and in vitro analysis showed that the polymorphisms were functionally significant. Genomic sequencing revealed noncoding polymorphism in both genes, in the promoter region of Cdc25A, and in the 3′ UTR of c- Myc. Among the genes identified by this method were the cell cycle-associated genes Cdc25A and c- Myc, both of which have been implicated in breast cancer. On the basis of the assumption that the loci were functioning in the same or intersecting pathways, a search of the literature databases was performed to identify molecular pathways containing genes from both candidate intervals. To identify potential candidate genes loci, a combined bioinformatics and genomics strategy was used. The epistatically interacting modifier loci ( Apmt1 and Apmt2) accelerate the polyoma Middle-T (PyVT)-induced mammary tumor.
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