Epigenetic regulation of cardiac neural crest cell development

Congenital heart diseases remain the leading cause of infant morbidity and mortality in developed countries. >30% of inborn heart defects are due to conotruncal abnormalities in the cardiac outflow tract and great arteries. Cardiac neural crest cells (cNCCs) are a major cell type participating in conotruncal development, and yet our current knowledge about epigenetic regulation of cNCCs remains highly limited. CHD7 encodes an ATP-dependent chromatin remodeling factor and is the main causal gene for CHARGE syndrome. ~70% of CHARGE patients display inborn heart defects with conotruncal anomalies being the most often observed forms. CNCC dysfunction has been proposed as the major cause for these conotruncal defects based on studies using in vitro cultured cells and an in vivo Xenopus CHARGE model. However, the cell autonomous role of CHD7 in cNCCs has not been supported by published mouse genetic studies, presenting a major knowledge gap regarding the activity of CHD7 in cNCCs and the developmental basis of the heart defects in CHARGE. In our unpublished study, we deleted Chd7 using Wnt1-Cre2, which is a recently established NCC-specific Cre driver to overcome a limitation of the original Wnt1-Cre. Mutant mice displayed severe conotruncal defects and died soon after birth. Therefore we provide the first mouse genetic evidence to support the essential cell autonomous role of CHD7 in cNCCs. Our mechanistic studies showed that CHD7 directly interacts with WDR5, which is a core component of H3K4 histone methyltransferase (HMTase) complexes. In this study, we will test our central hypothesis that CHD7 interacts with WDR5/HMTase complexes to regulate the epigenetic status of cNCC genes, promoting normal cardiovascular development. In Aim 1, we will determine how CHD7 epigenetically regulates Hand2 through its interaction with WDR5 in cNCCs. In Aim 2, we will reveal the regulatory target networks of CHD7 in cNCCs through unbiased high-throughput studies. This research is highly transformational and innovative. 1) Our data represent the first mouse genetic evidence to support the essential cell autonomous role of CHD7 in cNCCs. This study will help clarify contradictory results in the literature. 2) We show, for the first time, that CHD7 physically interacts with WDR5, which is a core component of the H3K4 HMTase complexes. We will thus test a novel mechanism by which a nucleosome remodeling factor crosstalks with the histone modification machinery. (AHA Program: Transformational Project Award)