Aberrant surface protein expression on Eklf-null mutant EryP. (A) CD24 is not expressed on Eklf^−/− EryP at E11.5 (top panel). By E14.5, a subpopulation of EryP/H2B-GFP have activated expression of CD24 to levels seen on EryD, while the remaining EryP/H2B-GFP fail to express CD24. (B) CD55 was modestly down-regulated on Eklf-null mutant EryP, while CD147 was moderately up-regulated. (C) FACS analysis of FL cells isolated from WT and Eklf mutant embryos. In comparison with the uniform levels of expression of α4, α5, and β1 integrins and CD44 on WT EryP/H2B-GFP, heterogeneous expression was seen on Eklf mutant EryP. (D) EryP/H2B-GFP Eklf^−/− FL cells from panel C were gated according to CD44 surface expression (gate A, expressed; gate B, not expressed). The corresponding levels of integrins α5 and β1 are shown.