Remodeling the cardiac sarcomere using transgenesis.

An underpinning of basic physiology and clinical medicine is that specific protein complements underlie cell and organ function. In the heart, contractile protein changes correlating with functional alterations occur during both normal development and the development of numerous pathologies. What has been lacking for the majority of these observations is an extension of correlation to causative proof. More specifically, different congenital heart diseases are characterized by shifts in the motor proteins, and the genetic etiologies of a number of different dilated and hypertrophic cardiomyopathies have been established as residing at loci encoding the contractile proteins. To establish cause, or to understand development of the pathophysiology over an animal's life span, it is necessary to direct the heart to synthesize, in the absence of other pleiotropic changes, the candidate protein. Subsequently one can determine whether or how the protein's presence causes the effects either directly or indirectly. By affecting the heart's protein complement in a defined manner, the potential to establish the function of different proteins and protein isoforms exists. Transgenesis provides a means of stably modifying the mammalian genome. By directing expression of engineered proteins to the heart, cardiac contractile protein profiles can be effectively remodeled and the resultant animal used to study the consequences of a single, genetic manipulation at the molecular, biochemical, cytological, and physiological levels.