Abstract 16484: The Transcriptional Repressor NR1D2 is Associated With Congenital Heart Disease and Plays an Evolutionarily Conserved Role in Cardiac Development

Abstract

Title: The Transcriptional Repressor NR1D2 is Associated with Congenital Heart Disease and Plays an Evolutionarily Conserved Role in Cardiac Development. Introduction: Congenital heart disease (CHD) is a leading cause of morbidity and mortality in young children and the underlying genetic etiology is complex and poorly defined. Recent genetic studies of mixed cardiac phenotypes focusing on de novo events have identified novel disease loci in up to 10% of participants and uncovered new functional categories of genes related to cardiac development. Hypothesis: We hypothesize that exome sequencing of patients with CHD will uncover novel genes related to cardiac disease and development. Methods: To identify disease-associated mutations, we analyzed exome sequencing data in a multi-institutional discovery cohort of 59 trios with a novel analytical pipeline. We phenotyped knockout animals for orthologous genes across multiple genetic phyla (mouse and fruit fly) for aspects of cardiac development. Additionally we performed Chromatin Immuno-Precipitation Sequencing (ChIP-seq) in a HL-1 mouse atrial cell line. Results: Exome sequencing uncovered a de novo missense variant R175W in the highly conserved DNA binding domain of NR1D2 a key component of the molecular clock. Knockout mice for Nr1d2tm1-Dgen display atrioventricular septal defects and related malformations, while knockdowns of the drosophila homolog Eip75B displays abnormal heart tube fusion during late embryonic development. ChIP-seq data for Nr1d2 suggests transcriptional repression at key loci controlling differentiation into both valve development (Twist1, Twist2, Bmpr1b) and atrial left-right patterning (Pitx2, Cited2). Conclusions: A patient with a deleterious de novo mutation in NR1D2 and knockout in multiple model organisms show cardiac defects, while genomic analysis of ChIP-seq data supports a modulatory role for this transcriptional repressor in the complex 3-dimensional process of cardiac morphogenesis. In conclusion, these data suggest that NR1D2 plays an evolutionarily conserved role in cardiac development and congenital heart disease. Further experiments are needed to understand the mechanism by which NR1D2 might link the molecular clock to cardiac development.