Cited2 controls left-right patterning and heart development through a Nodal-Pitx2c pathway

Abstract

Malformations of the septum, outflow tract and aortic arch are the most common congenital cardiovascular defects and occur in mice lacking Cited2, a transcriptional coactivator of TFAP2. Here we show that Cited2 -/-mice also develop laterality defects, including right isomerism, abnormal cardiac looping and hyposplenia, which are suppressed on a mixed genetic background. Cited2 -/-mice lack expression of the Nodal target genes Pitx2c, Nodal and Ebaf in the left lateral plate mesoderm, where they are required for establishing laterality and cardiovascular development. CITED2 and TFAP2 were detected at the Pitx2c promoter in embryonic hearts, and they activate Pitx2c transcription in transient transfection assays. We propose that an abnormal Nodal-Pitx2c pathway represents a unifying mechanism for the cardiovascular malformations observed in Cited2 -/-mice, and that such malformations may be the sole manifestation of a laterality defect.Genetic, developmental and molecular studies over the past decade have identified a number of DNA-binding transcription factors that have key roles in cardiac morphogenesis and in the pathogenesis of common congenital heart defects 1 . The role of transcriptional coactivators, molecules that connect DNA-binding transcription factors to the core transcriptional machinery, in cardiac development has only recently become apparent. These coactivators are exemplified by the paralogous genes EP300 and CREBBP 2 . Mutations in CREBBP cause Rubinstein-Taybi Syndrome 3 and are frequently associated with cardiac malformations 4 . EP300 and CREBBP interact with high affinity with a ubiquitously expressed cytokine and hypoxia-inducible transcriptional coactivator called CITED2 (also called p35srj and Mrg1) [5][6][7][8] . Binding of CITED2 to EP300 competitively inhibits the binding of the transcription factor HIF1A to EP300, blocking hypoxia-activated gene transcription 5,8 . Cited2 is essential for normal development of the heart, adrenals and nervous system 9-13 and for fibroblast proliferation 14 . Mice lacking Cited2 die prenatally with diverse cardiovascular malformations, including atrial and ventricular septal defects, double-outlet right ventricle, common arterial trunk and aberrant aortic arches.In addition to functioning as a transcriptional repressor of HIF1A, CITED2 also physically interacts with and coactivates TFAP2 (transcription factor AP2, also called Tcfap2) and LIM-domain containing transcription factors by linking them to EP300 and CREBBP 9,15,16 . Mutations in Tcfap2a and TFAP2B (Char syndrome) result in cardiac and aortic arch malformations 17,18 , suggesting that coactivation of TFAP2 by CITED2, EP300 and CREBBP is necessary for the normal development of these structures 9 . An alternative explanation for the development of cardiac malformations in mice lacking Cited2 is dysregulation of hypoxia-activated gene transcription 12 .The cardiovascular malformations resulting from deficiency of Cited2 encompass a diverse and variable spectrum that is not explained by effects on...

Post-transcriptional Control of Cited2 by Transforming Growth Factor β

“…Cited2 acts upstream of Nodal, a member of the TGF-␤ superfamily, and is required for normal establishment of the left-right axis (14,15). Overexpression of Cited2 in Rat1 cells results in loss of cell contact inhibition, anchorage-independent growth in soft agar, and tumor formation in nude mice, suggesting that Cited2 is a transforming gene (1).…”

Negative Feedback Regulation of NF-κB Action by CITED2 in the Nucleus

“…Further studies revealed left-right patterning defects in these embryos, especially in co-isogenic C57BL/6J backgrounds (26). Moreover, CITED2 could selectively maintain adult hemopoietic stem cell functions, at least in part via Ink4a/Arf and Trp53 (27).…”

Cited2 is required for normal hematopoiesis in the murine fetal liver

“…2 These initial in vitro studies underscore the potential roles of Cited2 in different biologic processes. Deletion of Cited2 gene results in embryonic lethality in the mid to late gestation with embryos displaying cardiac malformations, neural tube defects, 7 adrenal agenesis, [8][9][10] left-right patterning defects, 9,11 and placental defects. 12 Further mechanistic studies have provided evidence that Cited2 plays pivotal roles in these processes through its transcriptional modulator functions for HIF-1 8,13 or AP-2␣ signaling.…”

“…12 Further mechanistic studies have provided evidence that Cited2 plays pivotal roles in these processes through its transcriptional modulator functions for HIF-1 8,13 or AP-2␣ signaling. [9][10][11] Accumulated evidence has implicated the role of Cited2 in hematopoiesis because Bmi-1, which is essential for adult hematopoietic stem cell self-renewal, 14 is induced by Cited2 in mouse embryonic fibroblast (MEF) cells. 15 CBP and p300 are fate decision factors for HSCs, responsible for HSC self-renewal and hematopoietic differentiation, respectively.…”