Delineating Chromatin Accessibility Re-patterning at Single Cell Level during Early Stage of Direct Cardiac Reprogramming

Direct conversion of cardiac fibroblast into functional induced cardiomyocytes by forced expression of three cardiac transcription factors, Mef2c, Gata4, and Tbx5, holds great promise for regenerative medicine. Cardiac reprogramming consists of waves of transcription remodeling events, including the fast acquisition of cardiac program and the gradual loss of fibroblast program. However, how this transcription remodeling was driven by the upstream chromatin landscape is still unclear. In this study, we performed single-cell ATAC-seq on Day 3 cardiac reprogramming cells and unveiled networks of transcription factors (TFs) playing a pivotal role in the shift of chromatin accessibility during the early stage of cardiac reprogramming. Moreover, integration analysis of scRNA-seq and scATAC-seq lead to the identification of active TFs function as barriers to cardiac reprogramming. Single-cell ATAC-seq profiles of Day 3 cardiac fibroblast undergoing cardiac reprogramming were generated by 10x Genomics Chromium System.