Genetic analysis of growth control and development
My laboratory uses genetic and biochemical approaches to study mechanisms important in growth control and cancer. We have developed gene trapping strategies for genome-wide, biallelic mutagenesis of mammalian cells. Mutations in embryonic stem cells that affect specific genes of interest may be introduced into the germline; alternatively, biallelic mutagens may be used in phenotype-driven screens to identify genes responsible for recessive phenotypes in mammalian cells. We have used them to first approach to generate mice and cells defective in genes that are potentially involved in post-transcriptional gene regulation, [Ran GTPase activating protein, hnRNP A2/B1, hnRNP C, hnRNP U, TLS/Fus (hnRNP P2) and arginine methytransferase 1 (Prmt1)]. The genetic analysis of TLS/Fus, a gene translocated in human cancer, led to the unexpected discovery implicating this RNA binding protein in the maintenance of genome stability. The second approach has been used to identify candidate genes involved in Reovirus infection.
Studies to develop gene trap vectors provided basic information about transcript quality control, notably exon definition and nonsense-mediated decay, that govern the expression of gene segments inserted at ectopic sites in the genome. In addition, the collection of mutant stem cells has been used in genome-wide studies of spontaneous and carcinogen-induced LOH (loss of heterozygosity). The extent of LOH was remarkably high approaching 1% of the genome after brief exposure to nontoxic levels of carcinogens. These results highlight the importance of LOH as a somatic mutation and suggest that much of the LOH in cancer cells may result from prior exposure to genotoxic agents rather than from a state of chromosome instability during carcinogenesis. In addition, this work underscores the importance of genome maintenance in stem cells that serve as the normal cellular precursors to cancer. Current work in the lab is investigating the mechanisms of carcinogen-induced LOH.