Abstract
High-dimensional single cell profiling coupled with computational modeling holds the potential to elucidate developmental sequences and define genetic programs directing cell lineages. Here we introduce an approach to the discovery and exploration of developmental pathways based on the concept of “trajectory space”, in which cells are defined not by their phenotype but by their distance along nearest neighbor trajectories to every other cell in a population. We implement a tSpace algorithm, and show that multidimensional profiling of cells in trajectory space allows unsupervised reconstruction of complex developmental sequences. tSpace is robust, scalable, and implements a global approach to trajectory analysis that attempts to preserve both local and distant relationships in developmental pathways. Applied to high dimensional flow and mass cytometry data, the method faithfully reconstructs known branching pathways of thymic T cell development, and reveals patterns of tonsillar B cell development and of B cell migration. Applied to single cell transcriptomic data, the method unfolds the complex developmental sequences and genetic programs leading from intestinal stem cells to specialized epithelial phenotypes. Profiling of complex populations in high-dimensional trajectory space should prove useful for hypothesis generation in developing cell systems.
Footnotes
↵‡ shared authorship