TIMING IS EVERYTHING IN LIFE - CONDITIONAL TRANSGENE EXPRESSION IN THE CARDIOVASCULAR-SYSTEM

Manipulation of the mouse genome by traditional transgenic approaches has facilitated studies of gene function within the context of the int act organism and allowed for the creation of useful animal models of h uman disease. However, the timing of gene activation or repression is a critical determinant of phenotype, and the ability to regulate the t emporal profile of transgene expression remains an important experimen tal goal. In this Mini Review, we describe the current status of syste ms to tightly regulate target gene expression in vivo, focusing on bin ary systems using chimeric transcription factors. Although experimenta l difficulties persist, regulated expression systems are beginning to produce conditional phenotypes with exciting experimental implications . We review the experience to date and examine the potential utility o f these approaches within the context of cardiovascular medicine.