Cardiac fields and myocardial cell lineages
We focus on the origin of myocardial cells in the first and second heart fields in splanchnic mesoderm in the early embryo. Genetic lineage tracing using Cre recombinase activated conditional reporter genes has made a major contribution to our understanding of cardiac progenitor cells and will be discussed together with other experimental approaches to analysing cell lineages at the clonal level. Interactions between myocardial, epicardial and endocardial lineages are essential for coordinated function and homeostasis of the normal heart. Perturbation of heart field development and myocardial lineage contributions to the heart through developmental or acquired pathologies results in and modulates the progression of cardiac disease. Understanding the origin of myocardial lineages during embryonic development and how they converge to generate an integrated heart is thus a major biomedical objective. Furthermore, reactivation of developmental programmes is likely to be of major importance in strategies aimed at repair of the damaged heart.