With the dramatic development of single-cell RNA sequencing (scRNA-seq) technologies, the systematic decoding of cell-cell communication has received great research interest. To date, several in-silico methods have been developed, but most of them lack the ability to predict the communication pathways connecting the insides and outsides of cells. Here, we developed CellCall, a toolkit to infer inter- and intracellular communication pathways by integrating paired ligand-receptor and transcription factor (TF) activity. Moreover, CellCall uses an embedded pathway activity analysis method to identify the significantly activated pathways involved in intercellular crosstalk between certain cell types. Additionally, CellCall offers a rich suite of visualization options (Circos plot, Sankey plot, bubble plot, ridge plot, etc.) to present the analysis results. Case studies on scRNA-seq datasets of human testicular cells and the tumor immune microenvironment demonstrated the reliable and unique functionality of CellCall in intercellular communication analysis and internal TF activity exploration, which were further validated experimentally. Comparative analysis of CellCall and other tools indicated that CellCall was more accurate and offered more functions. In summary, CellCall provides a sophisticated and practical tool allowing researchers to decipher intercellular communication and related internal regulatory signals based on scRNA-seq data. CellCall is freely available at https://github.com/ShellyCoder/cellcall.

Low reprogramming efficiency and reduced pluripotency have been the two major obstacles in induced pluripotent stem (iPS) cell research. An effective and quick method to assess the pluripotency levels of iPS cells at early stages would significantly increase the success rate of iPS cell generation and promote its applications. We have identified a conserved imprinted region of the mouse genome, the Dlk1-Dio3 region, which was activated in fully pluripotent mouse stem cells but repressed in partially pluripotent cells. The degree of activation of this region was positively correlated with the pluripotency levels of stem cells. A mammalian conserved cluster of microRNAs encoded by this region exhibited significant expression differences between full and partial pluripotent stem cells. Several microRNAs from this cluster potentially target components of the polycomb repressive complex 2 (PRC2) and may form a feedback regulatory loop resulting in the expression of all genes and non-coding RNAs encoded by this region in full pluripotent stem cells. No other genomic regions were found to exhibit such clear expression changes between cell lines with different pluripotency levels; therefore, the Dlk1-Dio3 region may serve as a marker to identify fully pluripotent iPS or embryonic stem cells from partial pluripotent cells. These findings also provide a step forward toward understanding the operating mechanisms during reprogramming to produce iPS cells and can potentially promote the application of iPS cells in regenerative medicine and cancer therapy.