Gene-trap mutagenesis: Past, present and beyond

Although at least 35,000 human genes have been sequenced and mapped, adequa te expression or functional information is available for only similar to 15 % of them, Gene-trap mutagenesis is a technique that randomly generates los s-of-function mutations and reports the expression of many mouse genes. At present, several large-scale, gene-trap screens are being car ecl out with various new vectors, which aim to generate a public resource of mutagenized embryonic stem (ES) cells. This resource now includes more than 8,000 muta genized ES-cell lines, which are freely available, making it an appropriate time to evaluate the recent advances in this area of genomic technology an d the technical hurdles it has yet to overcome.