Dynamic alternative polyadenylation during iPSC differentiation into cardiomyocytes

Alternative polyadenylation (APA) is an important post-transcription regulatory mechanism widely occurring in eukaryotes and has been associated with special traits/diseases by several studies. However, the dynamic roles and patterns of APA in cell differentiation remain largely unknown. Here, we systematically characterized the APA profiles during the differentiation of induced pluripotent stem cells (iPSCs) to cardiomyocytes by the previously published RNA-seq data across 16 time points. We identified 950 differential APA events and found five dynamic APA patterns with fuzzy c-means clustering analysis. Among them, 3'UTR progressive lengthening is the main APA pattern over time, the genes of which are enriched in cell cycle and mRNA metabolic process pathways. By constructing the linear mixed-effects model, we also indicated that TIA1 plays an important role in regulating APA events with this pattern, including genes essential to cardiac function. Additionally, APA and polyA machinery activity with another pattern can immediately respond to developmental signal-mediated stimuli at the early differentiation stage and result in a sharp shortening of the 3'UTR. Finally, a miRNA-APA network is constructed and several hub miRNAs potentially regulating cardiomyocyte differentiation are detected. Our results show the complex APA mechanisms during the differentiation of iPSCs into cardiomyocytes and provide further insights for the understanding of APA regulation and cell differentiation.