The authors analyzed zebrafish embryos lacking expression of miR-128-1 and miR-128-2 (miR-128Δ/Δ), and observed increased numbers of hemECs and nascent HSPCs (nHSPCs) and an expansion of erythroid and lymphoid — but not myeloid — progenitors in secondary hematopoietic organs. Single-cell RNA sequencing of wild-type and miR-128Δ/Δ ECs isolated 26 hours post fertilization (hpf) indicated a continuum of cell differentiation states across EHT, including, for example, a cell cluster expressing both hemEC and nHSPC genes (defined as an EHT-undergoing cluster), one expressing genes priming lymphoid–erythroid progenitors (pLEPs) and one expressing genes priming lymphoid–myeloid progenitors (pLMPs). In the absence of miR-128, pre-EHT clusters and the cell cluster undergoing EHT were expanded, whereas the pLMP and pLEP clusters were not; although they displayed increased expression of the lymphoid marker ikzf1 and the erythroid marker gata1a, respectively.
Further analysis indicated that miR-128 expression peaks before and during EHT. Moreover, induced expression of miR-128 in the AGM of miR-128Δ/Δ embryos at 27 hpf could reverse the miR-128Δ/Δ nHSPC phenotype. These data and results from an EHT model using human pluripotent stem cells suggest that miR-128 expression in the AGM before hemogenic specification affects EHT and HSPC heterogeneity.
This is a preview of subscription content, access via your institution