The Cardiac TBX5 Interactome Reveals a Chromatin Remodeling Network Essential for Cardiac Septation

• Isolation and characterization of the endogenous cardiac TBX5 interactome
• TBX5 interacts biochemically and genetically with the NuRD repressor complex
• TBX5 represses inappropriate gene programs incompatible with cardiac development
• Human TBX5 mutations alter the NuRD interaction and correlate with septal defects

SummaryHuman mutations in the cardiac transcription factor gene TBX5 cause congenital heart disease (CHD), although the underlying mechanism is unknown. We report characterization of the endogenous TBX5 cardiac interactome and demonstrate that TBX5, long considered a transcriptional activator, interacts biochemically and genetically with the nucleosome remodeling and deacetylase (NuRD) repressor complex. Incompatible gene programs are repressed by TBX5 in the developing heart. CHD mis-sense mutations that disrupt the TBX5-NuRD interaction cause depression of a subset of repressed genes. Furthermore, the TBX5-NuRD interaction is required for heart development. Phylogenetic analysis showed that the TBX5-NuRD interaction domain evolved during early diversification of vertebrates, simultaneous with the evolution of cardiac septation. Collectively, this work defines a TBX5-NuRD interaction essential to cardiac development and the evolution of the mammalian heart, and when altered may contribute to human CHD.