Gene expression during cardiac development

The vertebrate heart forms as two concentric epithelial cylinders of myocardium and endocardium separated by an extended basement membrane matrix commonly referred to as cardiac jelly. Subsequent maturation involves a complex series of events including asymmetric changes in cell shape and division which contribute to bending and the formation of the bulboventricular loop, the formation of specialised tissues including endocardial cushion tissue of the atrioventricular (AV) and outflow tract regions, the development of conductive tissue and myocyte maturation leading to the overall pattern of expression characteristic of mature heart muscle. These processes depend on a precise spatial and temporal control of gene expression both of genes encoding regulatory molecules and those encoding structural components of the heart. In this chapter we address three aspects of cardiac development, namely, the determination of cell fate during formation of endocardial cushion tissue in the embryonic heart, transitions in troponin gene expression during fetal myocyte maturation, and the use of cloning techniques based on the polymerase chain reaction for identifying transcription factors present in the heart.