Retracing the in vivo haematopoietic tree using single-cell methods.

The dynamic process by which self-renewing stem cells and their offspring proliferate and differentiate to create the erythroid, myeloid and lymphoid lineages of the blood system has long since been an important topic of study. A range of recent single cell and family tracing methodologies such as massively parallel single-cell RNA-sequencing, mass cytometry, integration site barcoding, cellular barcoding and transposon barcoding are enabling unprecedented analysis, dissection and re-evaluation of the haematopoietic tree. In addition to the substantial experimental advances, these new techniques have required significant theoretical development in order to make biological deductions from their data. Here, we review these approaches from both an experimental and inferential point of view, considering their discoveries to date, their capabilities, limitations and opportunities for further development.