CONDITIONAL TRANSGENICS

Transgenic mice are important experimental systems for understanding t he regulation of gene expression and the function of various gene prod ucts within the complex environment of an intact organism. Re-combinan t genes are introduced into the mouse embryo and their patterns of exp ression or phenotypic effects are examined. Although current technolog y permits one to target expression of the transgene to many distinct c ell types, such as the cardiac myocyte, many experimental models requi re that gene expression be responsive to additional levels of control- a paradigm known as ''conditional transgene expression.'' Here, we des cribe the rationale for conditional transgenics, examine the systems t hat have been utilized to achieve highly regulated gene expression in vivo, and consider how these new, experimental approaches may improve our understanding of cardiovascular function and pathology.