Role of TET proteins during cardiac lineage specification
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abstract
Epigenetic regulation of cardiac gene expression plays a critical role in orchestrating early heart development and cardiac dysfunction. We recently discovered a novel family of epigenetic regulators, the Ten-eleven transition (TET) dioxygenases, which regulate DNA methylation by converting 5-methylcytosine (5mC) to further oxidized derivatives, with 5-hydroxylmethylcytosine (5hmC) as the most abundant species. We found that bisulfite sequencing, a method that is widely used to profile DNA methylome at genome-wide scale, fails to discriminate between 5mC and 5hmC, thus calling for an urgent overhaul to the current methylome data. The objectives of our project are to generate a dynamic map of cardiac hydroxylmethylomes and to elucidate the function of novel TET proteins during cardiac lineage specification. Findings from our published and own preliminary studies led us to hypothesize that Tet-mediated DNA demthylation orchestrates gene expression to mediate heart development. Empowered by a set of innovative toolkits tailored for genome-wide or loci-specific mapping and editing of DNA methylation, as well as single or combined Tet-deficient mouse models that are immediately available in the PI's laboratory, we are uniquely positioned to address the unmet challenges in two aims. In Aim 1, we will use mouse embryonic stem cells (mESC) as a model system to define how Tet proteins and 5hmC orchestrate cardiac lineage specification in vitro. We will ask i) how each Tet protein shapes the cardiac hydroxylmethylome landscape; and ii) how Tet/5hmC coordinates the gene expression network to drive mESC differentiation towards the cardiac lineage. In Aim 2, we will mechanistically dissect the interplays between Tet and Wnt signaling pathways and identify epigenetic signatures that are essential for cardiac lineage specification. We will also use our newly-devised epigenome editing tools to control DNA modifications at defined loci, with the goal of fine tuning cardiac tissue regeneration efficiency and ultimately rescuing developmental defects in heart. Accomplishment of our proposed epigenomic and mechanistic studies has the potential to lead to paradigm-shift advances in controlling cardiac development and heart regeneration. Discoveries made in this project will be crucial for deciphering the molecular etiology of congenital heart defects, as well as for designing better strategies to regenerate heart tissues for therapeutic purposes. (AHA Program: Innovative Research Grant)
