Use of human placental alkaline phosphatase transgenes to detect somatic mutation in mice in situ.

Methods for in situ detection of cells that have suffered a specific mutation would be valuable for understanding somatic genetic mosaicism, a phenomenon that underlies a variety of diseases including cancer. Such methods would also be valuable in studying changes in gene expression, whether programmed by the cells or caused by exogenous forces, such as exposure to genotoxins or infection by a virus. To improve methods for detection of genetic change at the cellular level in animal tissues, we used the human placental alkaline phosphatase (PLAP) gene. The PLAP gene sequence was modified such that it could no longer produce functional PLAP enzyme. Mutant PLAP genes were placed in the mouse genome, and populations of cells carrying these mutant PLAP genes were studied to determine the fraction of cells that would acquire PLAP activity. Spontaneous and induced reversion of mutant PLAP genes was studied in cultured cells and in the tissues of transgenic mice. The data obtained from these studies show the utility of in situ reporter genes such as PLAP for detection of variant cells within a tissue.