The objective of this research is to study chemical mutagenesis at the DNA level in mammals and to evaluate genetic and biochemical events in certain mutants as models of human genetic diseases. A major problem in mutagenesis is that the level and specificity of response is very different between indicator organisms; predictions about induced mutagenesis may not be relevant. Significant variation is due to the diversity of the marker genes; a single sequence needs to be used as a target in the various organisms and tissues. Our analysis is based on variance among single copies of the phi X174 virus containing am3 and cs70 mutations as a shuttle vector in different species. The accomplishments are as follows: 1) Techniques have been developed to recover chromosomally integrated phi X DNA and produce sufficient viable phages for the study of mutagenesis in cultures or tissues of transgenic mice. 2) The reversion frequency of am3 has been measured in progeny phage rescued from untreated mouse L-cells (5 X 10-), and cells treated with 20mM EMS (1.16 X 10-5). 3) New cell lines containing phi X have been produced. 4) Experiments are in progress to expand the indicator region of the phi X phage to provide detection of many more mutations in the integrated phage DNA. The use of integrated viral vector in transgenic mice can combine a theoretical study of mechanisms of mutation in several model organisms with an assessment of mutagenic hazard. A single DNA sequence can be exposed and analyzed as naked DNA, as a single stranded virus, double stranded in bacteria, and as vector DNA in the nuclear genome of mammalian cells or transgenic mice. In addition, we have characterized a new genetic mouse biochemical model of transient neonatal jaundice as a unique UDP-glucuronyl transferase deficiency. Adults homozygous for the mutation appear phenotypically normal in terms of the jaundice but remain enzymatically deficient throughout life. The enzymatic deficiency is accompanied by generalized necrosis and liver enlargement in older mutants. Work is in progress to determine whether the mutation is in the structural gene or perhaps regulatory.
