Molecular transitions in early progenitors during human cord blood hematopoiesis

Hematopoietic stem cells give rise to diverse cell types in the blood system, yet our molecular understanding of the earliest fate decisions that generate this enormous diversity in humans remains incomplete. Here we leverage Drop-seq to individually profile more than 20,000 progenitors cells from human cord blood, without prior enrichment or depletion for individual lineages based on surface markers. Our data reveal a transcriptional ''atlas'' of progenitor states in human cord blood, which we leverage to reconstruct differentiation trajectories from HSC to four downstream lineages. And we also demonstrate that Drop-seq data can be utilized to identify new heterogeneous markers of cell state. Overall design: CD34+ cells were enriched from human cord blood mononuclear cells, and mRNA profiles were generated by paired-end sequencing in Illumina HiSeq, with cDNA being amplified using the Drop-seq protocol, or a modified SMART-Seq2 protocol. Generally, 2-3 replicates were performed per biological sample.