During the last decade, gene expression in cardiac muscle of the developing embryo has
been examined in situ with the use of nucleic acid probes and antibodies. With growth and
maturation from a simple tube to a four-chambered organ, the myocardium undergoes a
complex series of developmental changes in the temporal and spatial expression patterns of
a number of structural and transcription factor genes. Studies of embryonic hearts suggest
that different populations of cardiac myocytes might appear during development. These in …