Transactivation in Drosophila of Human Enhancers by Human Transcription Factors Involved in Congenital Heart Diseases

Background: The human transcription factors (TFs) GATA4, NKX2.5 and TBX5 form part of the core network necessary to build a human heart and are involved in Congenital Heart Diseases (CHDs). The human natriuretic peptide precursor A (NPPA) and α-myosin heavy chain 6 (MYH6) genes are downstream effectors involved in cardiogenesis that have been demonstrated to be in vitro targets of such TFs. Results: To study the interactions between these human TFs and their target enhancers in vivo, we overexpressed them in the whole Drosophila cardiac tube using the UAS/GAL4 system. We observed that all three TFs up-regulate their natural target enhancers in Drosophila and cause developmental defects when overexpressed in eyes and wings. Conclusions: A strong potential of the present model might be the development of combinatorial and mutational assays to study the interactions between human TFs and their natural target promoters, which are not easily undertaken in tissue culture cells because of the variability in transfection efficiency, especially when multiple constructs are used. Thus, this novel system could be used to determine in vivo the genetic nature of the human mutant forms of these TFs, setting up a powerful tool to unravel the molecular genetic mechanisms that lead to CHDs. Developmental Dynamics 241:190–199, 2012. © 2011 Wiley Periodicals, Inc. KEY FINDINGS: The mammalian transcription factors GATA4, Nkx2.5 and TBX5 are able to transactivate the Nppa and Myh6 human enhancers in Drosophila embryos. The endogenous Drosophila homologs of GATA4, Nkx2.5 and TBX5 are not transactivated by GATA4, Nkx2.5 or TBX5, ruling out a possible endogenous regulatory circuit. Overexpression in the mesoderm of GATA4, Nkx2.5 or TBX5 is lethal and overexpression in eyes and wings causes reduced organs.