The transcription factor (TF) Islet1 (Isl1) is important for the development of a cardiac cell lineage in mouse called the second heart field,which contributes to certain heart structures. However, the precise role of Isl1 in the early regulatory network that specifies cardiac progenitors from mesoderm remains unresolved. Now, Petra Pandur and co-workers report that tailup (tup), the Drosophila homolog of Isl1, is required for early cardiogenesis in flies (see ). They show that Tup protein is expressed during cardiogenesis, and that tup is required for cardiac progenitor specification. In tup mutants, the expression of three conserved TFs (tinman/Nkx2.5,pannier/Gata4 and Dorsocross/Tbx5/6) that are part of the early cardiac regulatory network is downregulated. Conversely, Tup expression depends on each of these TFs. All four TFs interact genetically,and tup functions in both the ectoderm and mesoderm to regulate heart development. From their findings, the authors propose that tup is a crucial component of the early cardiac specification network, a role that might be conserved in vertebrates.
