BackgroundDNA methylation is a major epigenetic mechanism altering gene expression in development and disease. However, its role in the regulation of gene expression during heart development is incompletely understood. The aim of this study is to reveal DNA methylation in mouse embryonic hearts and its role in regulating gene expression during heart development.Methods and ResultsWe performed the genome‐wide DNA methylation profiling of mouse embryonic hearts using methyl‐sensitive, tiny fragment enrichment/massively parallel sequencing to determine methylation levels at ACGT sites. The results showed that while global methylation of 1.64 million ACGT sites in developing hearts remains stable between embryonic day (E) 11.5 and E14.5, a small fraction (2901) of them exhibit differential methylation. Gene Ontology analysis revealed that these sites are enriched at genes involved in heart development. Quantitative real‐time PCR analysis of 350 genes with differential DNA methylation showed that the expression of 181 genes is developmentally regulated, and 79 genes have correlative changes between methylation and expression, including hyaluronan synthase 2 (Has2). Required for heart valve formation, Has2 expression in the developing heart valves is downregulated at E14.5, accompanied with increased DNA methylation in its enhancer. Genetic knockout further showed that the downregulation of Has2 expression is dependent on DNA methyltransferase 3b, which is co‐expressed with Has2 in the forming heart valve region, indicating that the DNA methylation change may contribute to the Has2 enhancer's regulating function.ConclusionsDNA methylation is developmentally regulated for genes essential to heart development, and abnormal DNA methylation may contribute to congenital heart disease.

The normal murine placenta possesses several components of RAS, and in response to AMH several of these elements undergo important changes. In addition, differential expression of RAS mRNA, miRNA and protein, indicate post-transcriptional regulatory mechanisms involved with hypoxic stress, and necessitate further investigation.

Black maternal mortality is on the rise in the United States and cannot be fully explained by socioeconomic factors and limited access to care.[6] that of non-Hispanic white women5. Even in states such as California that appeared to buck the national trend (8.3/100,000), Black women still died at triple the rate (26.6/100,000) in that state (Figure 1) [6].Commonly cited reasons for the disparity observed include lower socioeconomic status and lack of prenatal care [7]. While each

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