Lothar Hennighausen (NIDDK)
Cre-recombinase under the control of the whey acidic acid protein was only detected in alveolar epithelial cells of mammary tissue during lactation, and transcription occurred at all stages of mammary development.
The Cre recombinase from bacteriophage P1 excises intervening DNA sequences located between two unidirectional lox sites positioned on the same linear DNA segment, leaving one lox site behind. Through insertion of lox sites via homologous recombination into the gene of interest and targeting Cre recombinase expression to a specific cell type using a tissue-specific promoter, it is possible to introduce predetermined deletions into the mammalian genome. To delete genes specifically from mammary gland, transgenic mice were created carrying the Cre gene under the control of the whey acidic protein (WAP) gene promoter. Expression of WAP-Cre was only detected in alveolar epithelial cells of mammary tissue during lactation. Recombination mediated by Cre under control of the WAP gene promoter was largely restricted to the mammary gland but occasionally was observed in the brain. High-level transcriptional activity of WAP-based transgenes can be obtained at every stage of mammary development.