Dynamic Visualization of DNA Methylation in Cell Cycle Genes during iPSC Cardiac Differentiation

Abstract

Epigenetic DNA methylation is an essential mechanism controlling gene expression and cellular function. Endpoint analyses with conventional assays have generated significant insights into static states of DNA methylation, but were short of visualizing the dynamics of epigenetic regulation. Here, we adopted a genomic DNA methylation reporter (GMR) system to track the changes of DNA methylation during cardiac differentiation. The promoter region of Cdk1 (Cyclin-dependent kinase 1) or Sox2 (SRY-Box Transcription Factor 2) gene was cloned upstream of the small nuclear ribonucleoprotein polypeptide N (Snrpn) minimal promoter followed by a fluorescent reporter gene. Mouse induced pluripotent stem cells (iPSCs) carrying Sox2 GMR rapidly lost fluorescent reporter signal upon the induction of differentiation. Cdk1 GMR reporter signal was strong in undifferentiated iPSCs, and gradually decreased during directed cardiomyocyte (CM) differentiation. The present study demonstrated the dynamic DNA methylation along the course of cell cycle withdrawal during CM differentiation. The GMR reporter system can be instrumental to monitor real-time epigenetic DNA modification at single-cell resolution.