Cardiac malformations, adrenal agenesis, neural crest defects and exencephaly in mice lacking Cited2, a new Tfap2 co-activator

The protein EP300 and its paralog CREBBP (CREB-binding protein) are ubiquitously expressed transcriptional co-activators and histone acetyl transferases'. The gene EP300 is essential for normal cardiac and neural development, whereas CREBBP is essential for neurulation, hematopoietic differentiation, angiogenesis and skeletal and cardiac development(2-5). Mutations in CREBBP cause Rubinstein-Taybi syndrome, which is characterized by mental retardation, skeletal abnormalities and congenital cardiac defects(6,7). The CBP/p300-interacting transactivator with ED-rich tail 2 (CITED2) binds EP300 and CREBBP with high affinity(8) and regulates gene transcription(8-10). Here we show that Cited2(-/-) embryos die with cardiac malformations, adrenal agenesis, abnormal cranial ganglia and exencephaly. The cardiac defects include atrial and ventricular septal defects, overriding aorta, double-outlet right ventricle, persistent truncus arteriosus and right-sided aortic arches. We find increased apoptosis in the midbrain region and a marked reduction in ErbB3-expressing neural crest cells in mid-embryogenesis. We show that CITED2 interacts with and co-activates all isoforms of transcription factor AP-2 (TFAP2). Transactivation by TFAP2 isoforms is defective in Cited2(-/-) embryonic fibroblasts and is rescued by ectopically expressed CITED2. As certain Tfap2 isoforms are essential in neural crest, neural tube and cardiac development(11-13), we propose that abnormal embryogenesis in mice lacking Cited2 results, at least in part, from its role as a Tfap2 co-activator.