Abstract
ABSTRACTDeletions of chromosome 1p36 are associated with a high incidence of congenital heart defects (CHDs). The arginine-glutamic acid dipeptide repeats gene (RERE) is located in a critical region for CHD on chromosome 1p36 and encodes a cardiac-expressed nuclear receptor co-regulator. Mutations affecting RERE cause atrial and ventricular septal defects (VSDs) in humans, and RERE-deficient mice also develop VSDs. During cardiac development, mesenchymal cells destined to form part of the atrioventricular (AV) septum are generated when endocardial cells in the AV canal undergo epithelial-to-mesenchymal transition (EMT) and migrate into the space between the endocardium and the myocardium. These newly generated mesenchymal cells then proliferate to fill the developing AV endocardial cushions. Here, we demonstrate that RERE-deficient mouse embryos have reduced numbers of mesenchymal cells in their AV endocardial cushions owing to decreased levels of EMT and mesenchymal cell proliferation. In the endocardium, RERE colocalizes with GATA4, a transcription factor required for normal levels of EMT and mesenchymal cell proliferation. Using a combination of in vivo and in vitro studies, we show that Rere and Gata4 interact genetically in the development of CHDs, RERE positively regulates transcription from the Gata4 promoter and GATA4 levels are reduced in the AV canals of RERE-deficient embryos. Tissue-specific ablation of Rere in the endocardium leads to hypocellularity of the AV endocardial cushions, defective EMT and VSDs, but does not result in decreased GATA4 expression. We conclude that RERE functions in the AV canal to positively regulate the expression of GATA4, and that deficiency of RERE leads to the development of VSDs through its effects on EMT and mesenchymal cell proliferation. However, the cell-autonomous role of RERE in promoting EMT in the endocardium must be mediated by its effects on the expression of proteins other than GATA4.This article has an associated First Person interview with the first author of the paper.
Highlights
Deletions of chromosome 1p36 are the most common terminal deletions in humans (Heilstedt et al, 2003a)
RERE colocalizes with GATA4, a transcription factor required for normal levels of epithelial-to-mesenchymal transition (EMT) and mesenchymal cell proliferation
Using a combination of in vivo and in vitro studies, we show that Rere and Gata4 interact genetically in the development of congenital heart defects, RERE positively regulates transcription from the Gata4 promoter, and GATA4 levels are reduced in the AV canals of REREdeficient embryos
Summary
Deletions of chromosome 1p36 are the most common terminal deletions in humans (Heilstedt et al, 2003a). 1 in 5000 newborns carries a terminal or interstitial deletion affecting chromosome 1p36. These children are at risk for a variety of medical problems—developmental delay, intellectual disability, brain malformations, eye defects, hearing loss, congenital heart defects (CHD), cardiomyopathy, renal anomalies, post-natal growth deficiency, and dysmorphic features— which, together, constitute the 1p36 deletion syndrome (Battaglia et al, 2008; Shapira et al, 1997). The arginine-glutamic acid dipeptide repeats gene (RERE) is located in the proximal critical region for 1p36 deletion syndrome and in one of the five 1p36 cardiac critical regions (Jordan et al, 2015; Zaveri et al, 2014). RERE encodes a nuclear receptor coregulator that is expressed in a wide variety of tissues, including the embryonic and adult heart, and has been shown to positively regulate retinoic acid signaling during development (Vilhais-Neto et al, 2010; Wang et al, 2008; Zoltewicz et al, 2004)
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