Cardiac Morphogenesis and Dysmorphogenesis I. Normal Development

In this chapter, we will provide the developmental biologist, interested in cardiac development, a schematic description of heart development. This chapter is not intended to describe in detail every aspect of cardiac morphogenesis in the vertebrate heart or to elaborate extensively on all the species-specific differences that can be found. Such an effort would take up a complete volume in this series. As the mouse (genetic models, i.e., knockouts, transgenes, and trisomies) and the chicken (experimental models, microinjection, and cell-tracing studies) are still the animals of choice for the study of cardiac development, we will concentrate on these two animal models and relate the observations described to relevant data in other species-in particular, human. In order to prevent confusion with the different staging protocols, we have summarized the most frequently used staging systems in Table 1. This table should facilitate the comparison of embryonic stages. Hence, chicken embryos are staged according to Hamburger and Hamilton (H/H) (1 ), the stages of the mouse embryos depicted in this chapter are given in embryonic days (ED) according to Theiler (2 ), and stages in human development are given in Carnegie Stages (CS) according to O’Rahilly and Mueller (3 ). We will discuss some of the basic concepts important for the understanding of cardiac development in normal and abnormal situations and briefly touch on the use of molecular markers to trace the fate of subpopulations of cells. In addition, we will describe the development of a few areas in the heart, those most frequently affected in animal model systems for congenital cardiovascular malformations, in a little more detail. If the information concerning normal and abnormal heart development provided in our chapters in this series of Developmental Biology Protocols does not suffice, we strongly encourage developmental biologists to seek assistance by, and collaborate with, cardiovascular embryologists.