Gene trap mutagenesis in mice: new perspectives and tools in cancer research.

The complete human DNA sequence of the human genome was published in 2004 and we entered the postgenomic era. However, many studies showed that gene function is much more complex than we expected, and that mutation of disease genes does not give any clue for molecular mechanisms for disease development. Since the first report on gene knockout mice in 1989, knockout mice have been shown to be a powerful tool for functional genomics and for the dissection of developmental processes in human diseases. In accordance with this successful application of knockout mice, three major mouse knockout programs are now underway worldwide, to mutate all protein-encoding genes in mouse embryonic stem cells using a combination of gene trapping and gene targeting. We developed the exchangeable gene trap method suitable for large scale mutagenesis in mice. In this method we can produce null mutation and post-insertional modification, enabling replacement of the marker gene with a gene of interest and conditional knockout. We herein discuss the effect of this gene-driven type approach for cancer research, especially for finding the genes that are related to cancer, but are paid little attention in hypothesis-driven cancer research.