Inducible Gene Trapping with Drug-Selectable Markers and Cre/loxP To Identify Developmentally Regulated Genes

Abstract

Gene trapping in mouse embryonic stem cells is an important genetic approach that allows simultaneous mutation of genes and generation of corresponding mutant mice. We designed a selection scheme with drug selection markers and Cre/loxP technology which allows screening of gene trap events that responded to a signaling molecule in a 96-well format. Nine hundred twenty gene trap clones were assayed, and 258 were classified as gene traps induced by in vitro differentiation. Sixty-five of the in vitro differentiation-inducible gene traps were also responsive to retinoic acid treatment. In vivo analysis revealed that 85% of the retinoic acid-inducible gene traps trapped developmentally regulated genes, consistent with the observation that genes induced by retinoic acid treatment are likely to be developmentally regulated. Our results demonstrate that the inducible gene trapping system described here can be used to enrich in vitro for traps in genes of interest. Furthermore, we demonstrate that the cre reporter is extremely sensitive and can be used to explore chromosomal regions that are not detectable with neo as a selection cassette.

We thank Hugo J. Bellen, Xiao-Zhong Wang, and Meredith Wentland for critical reading of the manuscript. We also thank Sukeshi Vaishnav, Sandra Rivera, Gabriele C. Schuster, and Janis Wesley for technical assistance in histological analysis, feeder cell preparation, chimera generation, and mouse colony maintenance and Sarah Quakkelaar-Howard for help preparing the manuscript.

This work was supported by grants to A.B. from the NIH National Cancer Institute.