Abstract
Direct reprogramming of cardiac fibroblasts (CFs) to induced cardiomyocytes (iCMs) is a newly emerged promising approach for cardiac regeneration, disease modeling, and drug discovery. However, its potential has been drastically limited due to the low reprogramming efficiency and largely unknown underlying molecular mechanisms. We have previously screened and identified epigenetic factors related to histone modification during iCM reprogramming. Here, we used shRNAs targeting an additional battery of epigenetic factors involved in chromatin remodeling and RNA splicing factors to further identify inhibitors and facilitators of direct cardiac reprogramming. Knockdown of RNA splicing factors Sf3a1 or Sf3b1 significantly reduced the percentage and total number of cardiac marker positive iCMs accompanied with generally repressed gene expression. Removal of another RNA splicing factor Zrsr2 promoted the acquisition of CM molecular features in CFs and mouse embryonic fibroblasts (MEFs) at both protein and mRNA levels. Moreover, a consistent increase of reprogramming efficiency was observed in CFs and MEFs treated with shRNAs targeting Bcor (component of BCOR complex superfamily) or Stag2 (component of cohesin complex). Our work thus reveals several additional epigenetic and splicing factors that are either inhibitory to or required for iCM reprogramming and highlights the importance of epigenetic regulation and RNA splicing process during cell fate conversion.
Highlights
Mammalian hearts have limited ability to regenerate, deleterious insult such as myocardial infarction (MI) can result in a permanent loss of cardiomyocytes (CMs) and a progressive decline in heart function [1]
We previously showed that removal of the key epigenetic barrier Bmi1 promotes the efficiency and quality of induced cardiomyocytes (iCMs) generated via transcription factor-mediated direct reprogramming [21]
In an effort to further examine the influence of additional epigenetic factors on iCM reprogramming, we used a similar loss-offunction screen to determine the role of 25 selected genes related to epigenetic modification and chromatin remodeling (Table 1)
Summary
Mammalian hearts have limited ability to regenerate, deleterious insult such as myocardial infarction (MI) can result in a permanent loss of cardiomyocytes (CMs) and a progressive decline in heart function [1]. Thereafter, a growing number of studies have been performed focusing on alternative cocktails that could improve efficiency and/or purity of iCMs [4, 6,7,8,9,10,11,12,13,14,15,16] and began to reveal the underlying molecular mechanisms during iCM reprogramming [17,18,19,20,21,22] Despite these advances, the potential of iCM approach to be used on patients is still limited because of
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