Mutation is a driving factor in many diseases, in particular cancer, but also diseases such as atherosclerosis. Mutation has been studied in human blood cells and other cell types that can be cultured. These mutation studies in humans have revealed increased mutation based on chemical exposure or tumor formation, but correlations between a particular gene or chemical are difficult due to the varied nature of the human population. Therefore mouse models of mutation have been developed since mice can be inbred and a particular gene can be isolated and studied.
There are many different mouse models of mutation, each with its own advantages and disadvantages. Some mouse models of mutation can measure a wide range of mutations but only in cell types that can be cultured. Other mouse models of mutation can measure a smaller range of mutations in all tissues, but the specific cell type is unknown. Still other mouse models of mutation can measure only a specific type of mutation, but in many tissues and in specific cell types. There is not yet a mouse that can measure all mutations, in all tissues, and in specific cell types.
I have studied two different mouse models of mutation: G11 PLAP and APRT. The G11 PLAP assay measures only one type of mutation (a frameshift), but the specific cell types that are mutated can be determined. The APRT assay measures many different kinds of mutation, but only in cell types that can be cultured.
The G11 PLAP assay showed that not only is there increased mutation upon chemical treatment and increasing age, but there is also an increase in proliferation. A cell that is mutated for G11 PLAP does not have a growth advantage; therefore PLAP can be an independent marker for cell proliferation. It was surprising to find an increase in proliferation with increasing age, since most organs are thought to have a low mitotic index in adulthood. The utility of the G11 PLAP assay to not only measure mutation, but also proliferation, has led me to the design of better mouse models that can detect of wider range of mutations, but still be in situ. I have developed a potential mouse model of mutation that can detect of wider range of mutations, but still be in situ.
The shYFP mouse model has a siRNA on one homologue and a fluorescent protein on the other homologue. A normal cell is dim, but upon loss of the siRNA, the cell becomes bright. This phenomenon was seen in both embryonic stem cells and intestinal epithelia. The loss of the siRNA was found to be from large chromosomal events, but smaller mutation events could also lead to loss of the siRNA. This is the first mouse model to measure many different mutational events in situ. I have continued to work on perfecting the model with slight variations with the ultimate goal to make a mouse that can measure many different kinds of mutation in any cell both rapidly and easily.