The landscape of chromatin accessibility in skeletal muscle during embryonic development in pigs

Abstract

Background: The development of skeletal muscle during the embryonic stage in pigs is precisely regulated by transcriptional mechanisms, which depends on chromatin accessibility. However, the landscape of chromatin accessibility in skeletal muscle during embryonic development in pigs has not been reported. To gain insight into the landscape of chromatin accessibility and the associated genome-wide transcriptome during embryonic muscle development, we performed ATAC-seq and RNA-seq on skeletal muscle of pig embryos at 45, 70 and 100 days post coitus (dpc).Results: In total, 21638, 35447 and 60181 unique regions (or peaks) were found across 45 dpc (LW45), 70 dpc (LW70) and 100 dpc (LW100) embryos, respectively. More than 91% of peaks were annotated within -1 kb to 100 bp of transcription start sites (TSSs). First, widespread increases in specific accessible chromatin regions (ACRs) from 45 to 100 dpc embryos suggested that the regulatory mechanisms became increasingly complicated during embryonic development. Second, the findings of integrated ATAC-seq and RNA-seq analyses showed that not only the numbers but also the peak intensities of ACRs could control the expression of associated genes. Finally, motif screening of stage-specific ACRs revealed some transcription factors that regulated muscle development-related genes, such as MyoD, Mef2c, and Mef2d. Motif screening of DPI of common peaks detected that a potential transcriptional repressor, namely CTCF, was identified among those genes that exhibited different change trends between the ATAC-seq and RNA-seq data.Conclusions: This work indicates that chromatin accessibility plays an important regulatory role in the embryonic muscle development of pigs and regulates the temporal and spatial expression patterns of key genes in muscle development by influencing the binding of transcription factors. Our results contribute to a better understanding of the regulatory dynamics of genes involved in pig embryonic skeletal muscle development.