HEART DEVELOPMENT IN DROSOPHILA AND ITS RELATIONSHIP TO VERTEBRATES

The discovery of the vertebrate hox gene clusters and their structural and functional relationship to the Drosophila HOM-C cluster of homeot ic genes revealed amazing similarities between the developmental mecha nisms by which a major body axis is formed in vertebrates and those of many invertebrates, possibly encompassing all multicellular organisms . Recent data suggest that heart development in Drosophila also resemb les vertebrate heart development in several fundamental aspects despit e the drastic morphologic differences between them. The discovery of t he homeobox gene tinman, which is expressed in the embryonic heart of Drosophila and is required for heart formation, made it possible to co mpare the determining factors of heart development between Drosophila and vertebrates. tinman has mouse, frog, and fish relatives with consi derable sequence similarity, and one of these genes is also specifical ly expressed in the developing heart. It appears that embryologic orig ins and morphogenic movements of heart progenitors, as well as gene ex pression patterns and possibly their functions, are similar in Drosoph ila and in vertebrates. If it is true that heart development is conser ved between Drosophila and vertebrates, then Drosophila, once again, c ould serve as a model system for vertebrate development.