The genes that drive heart-cell differentiation in vertebrates and Drosophi
la are similar, even though the Drosophila 'heart' is a simple tube and the
vertebrate heart is a multichambered physiologically complex organ. Mutati
onal analysis in mice and, as particular focus of this review, in zebrafish
, reveals the additional genes brought into play to fashion these evolution
arily 'new' organotypic components.