Dissecting cellular crosstalk by sequencing physically interacting cells

Crosstalk between neighboring cells underlines many biological processes, such as cell activation, differentiation and signaling. Current single-cell genomic technologies lack information of cell-cell interactions, as each cell is profiled separately following tissue dissociation. Here we present Physically Interacting Cells sequencing (PIC-seq), which combines fluorescently activated cell sorting of physically interacting cells along with massively parallel single-cell RNA-sequencing and computational modeling to systematically map in situ cellular interactions and characterize their molecular crosstalk. Focusing on interactions between T cells and dendritic cells (DC) in vitro and in vivo, we map T-DC interaction preferences, and discover regulatory T cells as the major T cell subtype interacting with DC. Analysis of T-DC pairs characterized interaction-specific transcription, including upregulation of a costimulatory program in rare interactions between pathogen-presenting DC and T cells. In summary, PIC-seq provides a new technology to profile cell-cell interactions and characterize interaction-specific pathways and target genes at high resolution. Overall design: Transcriptional profiling of thousands of single cells and doublets (PIC) from both in vivo and in vitro assays of interacting T and dendritic cells.