CXCR4 and hereditary elliptocytosis: The timing of this requirement for CXCL12 coincides with the detection of surface expression of its receptor CXCR4 on HSC precursors between E9 and E10, which is subsequently decreased by late E10, consistent with single-cell transcriptional analysis, which suggests Cxcr4 expression in HE is downregulated during the transition to pre-HSC by pseudotemporal ordering.