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Re-patterning of H3K27me3, H3K4me3 and DNA methylation during fibroblast conversion into induced cardiomyocytes. Stem Cell Res 2016 Mar;16(2):507-18



Pubmed ID


Pubmed Central ID




Scopus ID

2-s2.0-84959276987   72 Citations


Direct conversion of fibroblasts into induced cardiomyocytes (iCMs) offers an alternative strategy for cardiac disease modeling and regeneration. During iCM reprogramming, the starting fibroblasts must overcome existing epigenetic barriers to acquire the CM-like chromatin pattern. However, epigenetic dynamics along this reprogramming process have not been studied. Here, we took advantage of our recently generated polycistronic system and determined the dynamics of two critical histone marks, H3K27me3 and H3K4me3, in parallel with gene expression at a set of carefully selected cardiac and fibroblast loci during iCM reprogramming. We observed reduced H3K27me3 and increased H3K4me3 at cardiac promoters as early as day 3, paralleled by a rapid significant increase in their mRNA expression. In contrast, H3K27me3 at loci encoding fibroblast marker genes did not increase until day 10 and H3K4me3 progressively decreased along the reprogramming process; these changes were accompanied by a gradual decrease in the mRNA expression of fibroblast marker genes. Further analyses of fibroblast-enriched transcription factors revealed a similarly late deposition of H3K27me3 and decreased mRNA expression of Sox9, Twist1 and Twist2, three important players in epithelial-mesenchymal transition. Our data suggest early rapid activation of the cardiac program and later progressive suppression of fibroblast fate at both epigenetic and transcriptional levels. Additionally, we determined the DNA methylation states of representative cardiac promoters and found that not every single CpG was equally demethylated during early stages of iCM reprogramming. Rather, there are specific CpGs, whose demethylation states correlated tightly with transcription activation, that we propose are the major contributing CpGs. Our work thus reveals a differential re-patterning of H3K27me3, H3K4me3 at cardiac and fibroblast loci during iCM reprogramming and could provide future genome-wide epigenetic studies with important guidance such as the appropriate time window and loci to be utilized as positive and negative controls.

Author List

Liu Z, Chen O, Zheng M, Wang L, Zhou Y, Yin C, Liu J, Qian L


Ziqing Liu PhD Assistant Professor in the Physiology department at Medical College of Wisconsin

MESH terms used to index this publication - Major topics in bold

Cell Line
Cellular Reprogramming
DNA Methylation
Epigenesis, Genetic
Flow Cytometry
Mice, Transgenic
Microscopy, Fluorescence
Myocytes, Cardiac
Promoter Regions, Genetic
RNA, Messenger
Real-Time Polymerase Chain Reaction
SOX9 Transcription Factor
Transcription Factors
Transcriptional Activation
Twist-Related Protein 1
Twist-Related Protein 2