Intersecting signalling and transcriptional pathways in Drosophila heart specification

The Drosophila heart, also called the dorsal vessel, is a linear tube consi sting of two major cell types, namely cardioblasts which serve as cardiomyo cytes and pericardial cells which surround its outer surface. This organ is derived from segmental clusters of cells in the dorsal mesoderm during ear ly embryonic development. During the past few gears, genetic and molecular studies have led to significant advances in our understanding of the regula tory mechanisms that pattern the early mesoderm by defining these cell clus ters and ultimately specifying individual cells within them as heart progen itors. These studies established that the patterning events involve specifi c combinations of localized inductive signals that act in coned with mesode rm-autonomous transcription factors to achieve a progressive subdivision of the mesoderm. Some of the synergistic interactions between mesodermal tran scription factors and external signalling molecules have been defined at th e molecular level. With respect to the pericardial cells, the final specifi cation steps were found to employ cell-intrinsic lineage mechanisms. Becaus e of the many striking similarities between Drosophila and early vertebrate heart development, which appear to extend to the molecular level, these in sights will be of significant help in defining related events during verteb rate cardiogenesis.