PEAR1 is a potential regulator of early hematopoiesis of human pluripotent stem cells

Hemogenic endothelial (HE) cells are specialized endothelial cells to give rise to hematopoietic stem/progenitor cells during hematopoietic development. The underlying mechanisms that regulate endothelial-to-hematopoietic transition (EHT) of human HE cells are not fully understand. Here, we identified platelet endothelial aggregation receptor-1 (PEAR1) as a novel regulator of early hematopoietic development in human pluripotent stem cells (hPSCs). We found that the expression of PEAP1 was elevated during hematopoietic development. A subpopulation of PEAR1⁺ cells overlapped with CD34⁺CD144⁺CD184⁺CD73⁻ arterial-type HE cells. Transcriptome analysis by RNA sequencing indicated that TAL1/SCL, GATA2, MYB, RUNX1 and other key transcription factors for hematopoietic development were mainly expressed in PEAR1⁺ cells, whereas the genes encoding for niche-related signals, such as fibronectin, vitronectin, bone morphogenetic proteins and jagged1, were highly expressed in PEAR1⁻ cells. The isolated PEAR1⁺ cells exhibited significantly greater EHT capacity on endothelial niche, compared with the PEAR1⁻ cells. Colony-forming unit (CFU) assays demonstrated the multilineage hematopoietic potential of PEAR1⁺-derived hematopoietic cells. Furthermore, PEAR1 knockout in hPSCs by CRISPR/Cas9 technology revealed that the hematopoietic differentiation was impaired, resulting in decreased EHT capacity, decreased expression of hematopoietic-related transcription factors, and increased expression of niche-related signals. In summary, this study revealed a novel role of PEAR1 in balancing intrinsic and extrinsic signals for early hematopoietic fate decision.